Introduction

Hematopoietic cell transplantation (HCT) is a potentially lifesaving treatment for many diseases. With expansion to new indications, better international access and improved outcomes, the population of long-term HCT survivors is rapidly growing [1,2,3,4,5,6]. However, survivors face serious long-term medical issues, psychosocial challenges which often impact quality of life (QOL) and decreased life expectancy [7,8,9,10]. Consequently, prevention and recognition of late-effects, followed by prompt intervention are crucial to improving long-term survivor outcomes. Additionally, there is an urgent need to better understand the biology and patient experience of HCT late-effects, as well as the ideal health care delivery infrastructure to manage this growing population [11,12,13,14,15,16,17].

Previous guidelines for long-term survivors of HCT were produced as collaborative efforts by multiple societies in 2006 and 2012 [18,19,20,21,22,23]. To update guidelines and provide further geographic diversity, we convened a working group of experts from multiple international organizations as well as patient advocates (Fig. 1). We set out to design these recommendations to adapt to evolving treatment paradigms in transplantation and cellular therapy. The topics are organized by organ system or complication type. Tables have been created with recommendations by organ system, and supplemental tables are also available which include more detailed information. Due to the overall scope of the topic, several appendices are available. It should be noted that many late effects may take years or even decades to manifest and recommendations can generally be followed in perpetuity (unless otherwise specified); however, for some clinical situations discontinuation of screening may eventually be reasonable. Additionally, while these recommendations can be helpful at a population level, patient-specific risk-factors should also be considered, and these recommendations are not meant to replace the judgment or advice of clinicians caring for individual patients. Recommendations in this document rely heavily on expert consensus given the lack of prospective randomized trials for screening, prevention, or treatment [5]. Survivorship care may take many forms and these recommendations may be adapted as appropriate. Further, currently available data are derived largely from North American and European centers, which may not be generalizable to all populations and resource constraints may limit their implementation, especially in certain geographic regions. Consideration of local data-driven guidance is therefore valuable for survivorship care.

Fig. 1: International Societies Represented.
figure 1

American Society for Transplantation and Cellular Therapy (ASTCT), Asia-Pacific Blood and Marrow Transplantation Group (APBMT), Australia and New Zealand Transplant and Cellular Therapies (ANZTCT), Children’s Oncology Group (COG), Cell Therapy Transplant Canada (CTTC), Center for International Blood and Marrow Transplantation Research (CIBMTR), East Mediterranean Blood and Marrow Transplantation Group (EMBMT), European Society for Blood and Marrow Transplantation (EBMT), Latin American Bone Marrow Transplantation Group (LABMT), Pediatric Transplantation and Cellular Therapy Consortium (PTCTC), Sociedade Brasileira de Transplante de Medula Ossea (SBTMO).

Methodology

First, a core group of seven participants (SJR, NSB, BKH, CD, KSB, NSM, RP) reviewed the 2012 guidelines and suggested new topics for inclusion, areas to emphasize and changes in formatting. These suggestions were reviewed with the larger group of 30 participants, additional changes were suggested and implemented, and the overall format was agreed upon. Subgroups of two to four members reviewed relevant literature to draft topic section content and recommendations; all participants had the opportunity to provide feedback. All participants were then surveyed to determine agreement with each screening, prevention, and treatment recommendation. The recommendation was adopted if ≥85% agreement occurred but were further edited before a second round of voting if <85%. If >50% consensus could ultimately not be reached, the recommendation was abandoned. Specific recommendations were then categorized similar to the National Comprehensive Cancer Network (NCCN) approach; all were deemed 2A or 2B indicating lower level of evidence with uniform consensus (2A, ≥85%) or consensus (2B, >50% to <85%) [24].

Hematopoietic complications

Common hematopoietic complications include autoimmune cytopenias (AICs), clonal hematopoiesis of indeterminate potential (CHIP), iron overload, and venous thromboembolism (VTE). Mixed chimerism may also present challenges for some patients (Table 1, Supplementary Table 1). AICs can occur weeks to years after allo-HCT, with risk factors including younger age, non-malignant disease, umbilical cord blood graft source, unrelated or haploidentical donors, conditioning with anti-thymocyte globulin (ATG) or alemtuzumab, absence of TBI, presence of GVHD and Cytomegalovirus (CMV) reactivation [25,26,27]. Cytopenias should prompt etiological investigations, especially to exclude auto-immunity or therapy-related myeloid neoplasm (tMN; see subsequent malignant neoplasms); treatment is based on underlying etiologies.

Table 1 Hematologic Complications.

The clonal expansion of hematopoietic progenitors in CHIP appears to be due to age-associated somatic mutation, without overt hematologic malignancy [28,29,30]. CHIP is associated with the development of subsequent hematologic malignancies as well as cardiovascular disease in the general population [28,29,30], and inferior overall survival, increased risk of tMN, and higher rates of cGVHD in the HCT setting [31, 32]. Data are currently too sparse to make specific recommendations regarding CHIP-associated late effects monitoring. However, all survivors should undergo an individualized cardiovascular disease risk assessment (see cardiovascular disease) and CHIP may be considered among those risk factors.

Iron overload from pre-HCT transfusion burden is common and patients with disorders associated with ineffective erythropoiesis are particularly at risk [33]. Post-HCT iron-overload is associated with infections, chronic liver disease, pituitary dysfunction, glucose dysregulation, and cardiomyopathy [33]. Survivors of both autologous and allogenic HCT are at increased risk for VTE [34,35,36,37], and long-term HCT survivors with a history of VTE have greater non-relapse mortality [38]. Risk factors include indwelling catheters, acute or cGVHD, infections, prolonged immobilization, HCT for malignancy, endothelial damage from conditioning, and prior history of VTE [34,35,36, 39, 40]. Patients receiving immune-modulatory drugs for myeloma are also at higher risk.

Immunity and infections

HCT survivors are at risk for developing infections and autoimmune diseases post-HCT, however, significant gaps still remain in our knowledge of immune dysfunction as a late-effect of HCT [16]. Infection is a significant cause of late mortality after allogeneic HCT, even in individuals without cGVHD [7, 8, 41]. Late CMV infections are most commonly seen in those with early CMV, cGVHD, and late immune manipulation (e.g. lymphocyte infusions). Other viral infections that may lead to significant hospitalization, morbidity, and mortality are varicella zoster virus (VZV), influenza, and coronavirus disease 2019 (COVID-19) [42, 43]. Survivors are also at risk for Epstein Barr virus (EBV) post-transplant lymphoproliferative disorder (PTLD) (see subsequent malignant neoplasms) and hepatitis B and C (see gastrointestinal complications). Several risk factors affect the incidence of late fungal infections, including cGVHD with ongoing immunosuppression, history of relapse, age, underlying disease, type of conditioning (especially with total body irradiation; TBI), umbilical cord blood graft source, and the use of T-cell depletion (Table 2, Supplementary Table 2) [16, 44,45,46]. Pneumocystis jiroveci pneumonia (PJP) is rare unless there is non-adherence with prescribed prophylaxis, though when it does occur, mortality rate is high [47,48,49]. Finally, bacterial infections pose a risk for long-term survivors with asplenia, cGVHD, central lines, those who are unvaccinated, or who have other risk factors.

Table 2 Immunity and infections.

General guidelines for prophylaxis and treatment of HCT associated infections (both early and late), and advice for safe living are beyond the scope of these recommendations, and have been reviewed elsewhere [46, 50,51,52,53,54,55,56,57,58]. Dietary restrictions, and returning to work or school practices also lack uniform agreement [59,60,61]. Nonetheless, chronically immune suppressed patients should be aware of infection risks, how to recognize symptoms and signs of infection and adhere to antimicrobial prophylaxis and vaccination guidelines.

Vaccine-preventable late infections are three times more common among ≥2 year-HCT vs non-HCT cancer survivors and >30 times more common compared to the general population [45]. All survivors should be offered a full vaccination program according to published guidelines taking into account patient age and country recommendations [62,63,64,65] These are detailed in reports from the Infectious Disease Society of America and the 2017 European Conference on Infections in Leukemia (Appendix 1) [62, 66, 67]. As of this publication, vaccination for COVID-19 is recommended to begin at 100 days post-HCT, though immunogenicity remains variable, and this is a rapidly changing area [68,69,70].

Routine use of intravenous immune globulin (IVIg) for hypogammaglobulinemia in adults is generally not recommended as no survival advantage or infection prevention has been demonstrated with routine use in unselected patients after HCT [71], and potential side effects exist. However, certain populations may benefit from IVIG supplementation [56, 71,72,73,74,75,76,77,78].

Ocular complications

Ocular complications after HCT can be broadly divided into GVHD and non-GVHD related, although overlap often exists (Table 3, Supplementary Table 3) [79,80,81,82,83,84,85]. Lacrimal gland dysfunction is the most common feature of ocular GVHD. Conjunctival involvement in GVHD is rare in children but more frequent in adults. Dry eyes can also be seen with radiation effects, chemotherapy, lid dysfunction, medications, and meibomian gland dysfunction. Post-HCT cataract formation has been associated with glucocorticoid treatment for GVHD, busulfan conditioning or TBI [85]. Glaucoma may be a late complication of TBI, though systemic or topical corticosteroid therapy for cGVHD can also elevate intraocular pressure in susceptible patients, with children being at greater risk. Infectious complications include viral bacterial, fungal, and toxoplasma. Retinal hemorrhage and detachment are rare but can be associated with CMV retinitis or neovascularization associated with ischemic retinopathy.

Table 3 Ocular, oral and dental complications.

Oral and dental complications

Oral and dental complications may result from cGVHD, chemotherapy and radiation (Table 3, Supplementary Table 4). Oral cGVHD is common and can involve the mucosa, salivary glands (xerostomia), oral and lingual muscles, taste buds, and gingiva. Patients may report oral pain, dryness, odynophagia, dysphagia, and sensitivity to normally tolerated flavors [79, 86, 87]. Gingivitis due to cGVHD may further limit teeth brushing. Presence of cGVHD is also a risk factor for squamous cell cancer (see subsequent malignant neoplasms) [88,89,90,91,92,93,94]. Late complications also include increased dental demineralization and caries, teeth staining, gingival enlargement, symptomatic acute periodontal infections, and asymptomatic chronic periodontal infections [95]. Salivary gland dysfunction predisposes to caries, oral herpes simplex and candidiasis, mechanical and epithelial injuries, and impairs tooth mineralization [96]. Protracted xerostomia may also occur in patients without cGVHD due to chemotherapy, radiation, or as medication side effect. Chemoradiotherapy exposure may disturb dental development in 50–80% of children; younger age at HCT and TBI are important risk factors [95, 97]. TBI may also lead to mandibular underdevelopment and mandibular joint anomalies. Routine dental care is imperative for optimal oral health. Frequent self and professional oral examination are the mainstay for early diagnosis of oral cancer. Patients should report lesions that do not heal, localized pain, leukoplakia, or other mucosal changes.

Respiratory complications

Late pulmonary complications include idiopathic pneumonia syndrome (IPS), pulmonary fibrosis, bronchiolitis obliterans syndrome (BOS), and cryptogenic organizing pneumonia (COP; Table 4, Supplementary Table 5) [22]. IPS usually develops within the first 120 days post-HCT, although later cases can occur. IPS increases the risk of transplant-related mortality and is thought to be multi-factorial, with risk factors including allogeneic HCT, chest radiation or TBI, certain chemotherapies, increasing age, and GVHD [98,99,100]. Pulmonary fibrosis may occur late after transplant and is generally characterized by pre- or post-HCT lung injury with specific risk factors including radiation, bleomycin, busulfan, carmustine, smoking, a history of acute lung injury, or posttransplant CMV pneumonitis.

Table 4 Respiratory complications.

BOS is considered a lung manifestation of cGVHD often diagnosed within the first two years post-HCT [101,102,103,104]. Patients may initially be asymptomatic, making diagnosis difficult without screening. cGVHD is the most important risk factor for developing BOS; other factors include aGVHD, lung toxic medications, ABO incompatibility, peripheral blood grafts, and early post-HCT viral infections [101, 105]. Early detection and treatment of BOS impacts outcomes. The use of NIH diagnostic criteria usually establishes the diagnosis of BOS without needing a lung biopsy [79]. Cryptogenic organizing pneumonia, previously known as bronchiolitis obliterans organizing pneumonia (BOOP), typically presents <1 year post-HCT with fever, cough and dyspnea; chest CT imaging shows solitary or multifocal pulmonary infiltrates, while PFTs classically show a restrictive pattern [106, 107]. While cGVHD is a risk-factor, other risks include drug toxicity, radiation, HLA-mismatch, donor-recipient sex mismatch, and use of peripheral blood grafts [107,108,109]. The diagnoses of IPS, COP and BOS can be confirmed through lung biopsy, however, less invasive means are typically sufficient. IPS and COP are diagnoses of exclusion and typically requires a bronchoalveolar lavage to rule out infection.

Cardiac and vascular complications

Cardiovascular complications occur frequently and contribute to late mortality and include hypertension (see renal and urinary complications), dyslipidemia, congestive heart failure, arrhythmias, valvular heart disease, premature coronary artery disease, stroke (see neurological and cognitive complications), CHIP (see hematopoietic complications) and peripheral vascular disease (Table 5, Supplementary Table 6) [17, 22, 110,111,112,113,114,115,116,117,118,119]. Metabolic syndrome (MetS) includes parameters that together increase the risk for diabetes and cardiovascular disease and is associated with increased all-cause mortality. The prevalence of MetS among HCT survivors is 31–53% which is increased compared to background populations [120,121,122]. Diagnostic criteria include presence of visceral obesity, increased blood pressure, hyperglycemia or insulin resistance, high triglycerides or low HDL [123]. Allogeneic HCT recipients have a higher incidence of abdominal obesity, lipid disorders, and impaired glucose metabolism than autologous recipients, which may be due to glucocorticoids, sirolimus, calcineurin inhibitors (CNI), alloreactivity, cranial radiation and TBI [121, 124,125,126,127,128,129,130]. TBI has been associated with hyperglycemia, diabetes and dyslipidemia, and pancreatic irradiation can lead to diabetes, whereas GVHD has also been associated with hypertension [128, 131,132,133]. Ischemic events are more frequent after allogeneic compared to autologous HCT [134]. Hypertension, diabetes, dyslipidemia, smoking, sedentarism and obesity have been identified as important, additive risk factors [114, 134, 135]. Cardiomyopathy and heart failure are strongly related to anthracycline exposure (particularly cumulative doses ≥ 250 mg/m2), hypertension, history of chest irradiation, diabetes and age, whereas TBI or conditioning intensity have yielded conflicting results [114, 116, 136]. As genetic polymorphisms play a role in anthracycline related cardiomyopathy, there is no clear ‘safe dose’ of anthracyclines [137]. It is important to note that cardiovascular events increase in incidence with greater time since HCT [134], and the presence or absence of cardiovascular disease or echocardiographic findings soon after HCT do not necessarily predict the risk of long-term cardiac toxicities.

Table 5 Cardiac and vascular complications.

Gastrointestinal complications

Long-term gastrointestinal complications of HCT involve luminal and solid organs (Table 6, Supplementary Table 7). cGVHD of the gastrointestinal tract may lead to dysphagia, esophageal webs, strictures and stenosis [138]. Previous radiation therapy (e.g., mediastinal for Hodgkin lymphoma) may also increase the risk for esophageal strictures [139]. Esophageal cGVHD and/or targeted radiation or TBI are risk factors for esophageal cancer (see subsequent malignant neoplasms) [94, 139, 140]. Likewise, luminal strictures may occur in patients with a history of severe gastrointestinal GVHD, abdominal surgery or abdominal radiation, and may be considered in the differential diagnosis of intermittent abdominal pain or small bowel obstruction [141]. Abdominopelvic radiation also increases the risk for colon cancer in childhood cancer survivors(see subsequent malignant neoplasms) [142,143,144].

Table 6 Gastrointestinal, renal, and urinary complications.

Hepatic complications may be multifactorial and potentially associated with GVHD, infections, medication, underlying acquired and genetic liver disease, and iron overload (see hematopoietic complications). Focal nodular hyperplasia is a common incidental radiological finding that may be associated with oral contraceptive use, younger age at HCT, abdominal radiation, and appears to occur frequently in children with Neuroblastoma [145,146,147,148]. Although malignant transformation is uncommon [146], consultation with a hepatologist may be warranted with lesion growth or diagnostic uncertainty [148]. The prevalence of chronic hepatitis B virus (HBV) infection varies widely depending on patient age and geographic location. HBV antibody titers may not be detectible due to immunosuppression and should not be entirely relied upon. Pre-HCT chronic HBV infection (surface antigen positive) or resolved HBV infection (core antibody positive but surface antigen negative) may result in fulminant post-HCT hepatitis [149, 150]. Survivors with chronic HBV infection need regular monitoring to assess viral load, liver status, need for antiviral therapy and are usually referred to a hepatologist. Hepatitis C virus infection (HCV) usually results in chronic hepatitis presenting as asymptomatic ALT elevation 2–4 months post-HCT when IST is tapered; chronic HCV may cause little liver-related mortality in the first 10 years but is the leading cause of post-HCT cirrhosis [111, 151, 152].

Although uncommon, most pancreatic complications relate to biliary stone passage or, rarely, to tacrolimus-associated pancreatic damage [153]. Pancreatic exocrine insufficiency occasionally presents with steatorrhea and weight loss despite adequate caloric intake. Its pathogenesis is speculative but thought to involve pancreatic atrophy from prior damage, possibly GVHD-associated; response to a trial of enzyme supplementation may be diagnostic [154].

Renal and urinary complications

Renal and urinary complications after HCT include chronic kidney disease (CKD), transplant associated-thrombotic microangiopathy (TA-TMA), nephrotic syndrome (NS), and hypertension. CKD can be caused by a number of pre-, peri- and post-HCT exposures with risk factors including previous acute kidney injury (AKI), GVHD, increased age at HCT, baseline renal insufficiency, hypertension, and TBI [22, 155]. Most cases of CKD are multifactorial due to an accumulation of peri-transplant events and/or risk factors (Table 6, Supplementary Table 8). The cumulative incidence of CKD varies from 7 to 48% and may develop from 6 months to 10 years after HCT, with ~4% progressing to end-stage renal disease [155]. Progressive glomerular filtration rate declines are associated with increasingly higher risks for mortality [156]. TA-TMA is a well-recognized complication but diagnosis has often been delayed and confounded [157,158,159]. TA-TMA occurs most frequently early post-HCT, but may occur late after HCT often in association with cGVHD [157,158,159,160]. Elevated lactate dehydrogenase, rising urine-protein-to-creatinine ratio, and hypertension are the earliest markers of TA-TMA, and should prompt clinicians to pursue further workup [111, 155]. NS is usually characterized by ≥2 of proteinuria, hypoalbuminemia, edema, most often after immunosuppression has been tapered for GVHD (at 6-12 months post-HCT) [17, 155]. As many as 70% of patients develop hypertension <2 years post-HCT [17, 155]. Known risk factors include CNI therapy, AKI, TBI, autologous transplant, obesity, and diabetes [155]. Effective antihypertensive therapy is important for reducing cardiovascular disease risks (See cardiac and vascular complications) and progression of CKD3 [17].

Endocrine complications

HCT survivors are at risk of developing growth impairment, gonadal insufficiency and infertility, thyroid dysfunction, and adrenal insufficiency. Growth can be impacted by multiple factors, including treatment exposures and post-HCT complications (Table 7, Supplementary Table 9) [161]. The incidence of post-HCT growth hormone (GH) deficiency due to hypothalamic-pituitary injuries varies from 20 to 85% [162,163,164,165]. Cranial irradiation (particularly ≥18 gray) and TBI are established risk factors; the final growth impact depends on age at exposure, patient sex, dose of and time since radiation [162, 166,167,168,169,170,171]. Nutritional deficiencies may also impact growth and development. The prevalence of gonadal dysfunction exceeds 90% in some studies and can manifest as delayed pubertal development or otherwise as gonadal insufficiency and infertility (see sexual health, fertility, and pregnancy) [64]. If untreated, it may lead to sexual dysfunction, low bone mineral density, cardiovascular disease, and poor QOL [172]. TBI, cranial or gonadal irradiation, alkylating agents, and platinum chemotherapy are risk factors; age at exposure may also impact the risk. Thyroid dysfunction is the most common post-HCT endocrinopathy with prevalence ranging from 10 to 47% [173,174,175,176]. Hypothyroidism is diagnosed at a median of 4 years post-HCT, although the risk persists longer [174]. Risk factors for thyroid dysfunction are younger age, head and neck radiation, high-dose TBI, busulfan and cyclophosphamide conditioning, and prolonged cGVHD [174, 175, 177,178,179]. Primary adrenal insufficiency is uncommon; most adrenal insufficiency is secondary due to prolonged glucocorticoid treatment which suppresses the hypothalamic–pituitary–adrenal axis [180].

Table 7 Endocrine complications.

Sexual health, fertility and pregnancy

Sexual health, fertility, and pregnancy concerns of HCT survivors is summarized in Table 8 and Supplementary Table 10. Approximately one third of survivors report inability to perform sexually, inability to derive pleasure from sex, and/or little or no interest in sex [181, 182]. Women are more likely than men to report being sexually inactive in the preceding year (39% versus 27%) and, among those sexually active, to report low sexual function (64% versus 32%) [183]. Factors associated with being sexually inactive include older age, less than four years college education, low clinical performance status, and not being in a committed relationship. Additional factors for men include non-myeloablative conditioning and not being employed or in school. Lower sexual function has also been associated with TBI in males, and cGVHD for men and women [181,182,183,184,185,186].

Table 8 Sexual health, fertility and pregnancy.

HCT is associated with infertility due to pre-transplant and transplant-related treatment exposures and late effects [187, 188]. Female sex, pre-HCT cytotoxic therapy, myeloablative conditioning and germ cell tumor diagnosis have been associated with lower fertility post-HCT [189]. Underlying conditions may also impact fertility (e.g., Fanconi anemia). In females, the degree of ovarian damage is related to the dose and type of exposure (e.g., myeloablative conditioning, radiation) as well as ovarian reserve which is dependent on age and previous treatment. Alkylating agents have the highest age-adjusted odds ratio of ovarian failure [188, 189]. The TBI dose that is potentially sterilizing appears to decrease with increasing age [189, 190]. In males, chemoradiotherapy can impair spermatogenesis, but testosterone levels generally remain normal because Leydig cells are relatively resistant. Lower testosterone can be seen when affected by GVHD, particularly in the setting of chronic glucocorticoid exposure [191]. For women, embryo and oocyte cryopreservation remain the preferred methods of fertility preservation. Ovarian tissue cryopreservation is becoming increasingly successful and remains the only option for pre- pubertal patients [192]. Despite success in animal models, the clinical value of GnRH agonists to preserve ovarian function during chemotherapy remains uncertain [193]. Sperm cryopreservation is an established fertility preservation option for post-pubertal males. In pre-pubertal males, the only option is testicular tissue cryopreservation; although animal models are encouraging, there have been no reports to date of re-implanted testicular tissue leading to human live births [188].

Uterine radiotherapy exposures may lead to adverse reproductive outcomes [194]. Increased rates of infertility, miscarriage, preterm labor, intrauterine growth restriction and low birth weight have been described, particularly if conception occurred within a year of radiotherapy [188, 195]. However, when women have not received radiation, miscarriage rates have been comparable to the background population without a significant increase in congenital malformations or genetic abnormalities [196, 197]. Similarly, reported pregnancies and deliveries from partners of male recipients have usually been uncomplicated [191].

Muscle and connective tissue complications

Muscle and connective tissue complications after HCT are often associated with cGVHD and its treatment and include glucocorticoid-induced myopathy, fasciitis/deep sclerosis, polymyositis, and myasthenia gravis, and are summarized in Table 9 and Supplementary Table 11 [198,199,200,201,202,203,204]. Steroid myopathy typically presents with proximal muscle weakness, difficulty rising from a squatting position, then atrophy of these muscle groups. While improvement in strength may occur 2–3 weeks after steroid reduction, complete resolution can take longer. Fluorinated glucocorticoids (e.g. dexamethasone) are associated with a higher risk of myopathy than non-fluorinated glucocorticoids (e.g. prednisolone) [205]. While significant variability in individual susceptibility to myopathy is observed, ≤10mg/day of prednisone or equivalent are unlikely to result in myopathy but ≥40mg/day for ≥1 month usually causes weakness [205].

Table 9 Musculoskeletal, connective tissue, skeletal, and dermatologic complications.

Fasciitis and polymyositis are cGVHD manifestations [203, 206, 207]. Fasciitis may cause tightness or restricted range of motion on the Photographic Range of Motion Scale [206], with combinations of visibly tight tendons in volar forearms/palms, palpable deep tissue sclerosis with overlying hyperpigmentation and “groove’ signs. Along with cGVHD treatment patients with fasciitis may benefit from a multidisciplinary rehabilitation program to control edema and preserve range of motion. Polymyositis usually presents with moderate to severe proximal muscle weakness and myalgia [199]. Myasthenia gravis is a rare cGVHD complication that may be due to donor-derived antibodies against recipient acetylcholine receptors and manifests similar to classic myasthenia gravis with most cases occurring >2 years post-HCT [204, 208].

Skeletal complications

Skeletal complications following HCT include abnormal bone density and avascular necrosis (AVN). Low bone mineral density (BMD) or osteopenia is a common complication that if untreated may lead to osteoporosis and increased risk for bone fragility fractures (Table 9, supplemental Table 12). The prevalence of low BMD is up to 75% among allogeneic HCT survivors and 65% in autologous HCT survivors [209]. Low BMD can be seen as early as one month post-HCT, and often persists beyond three years post-transplant [210,211,212,213,214,215,216,217]. Patient risk-factors include extremes of age at HCT, female sex, low body weight or body mass index, inadequate calcium or vitamin D intake, physical inactivity, renal dysfunction and hypogonadism. Disease-related risk factors include myeloma, hemophagocytic lymphohistiocytosis, hemoglobinopathies, and pre-HCT chemotherapy exposures [218]. Lastly, HCT-related risk factors include TBI or craniospinal irradiation, GVHD, and prolonged IST including CNIs and glucocorticoids [210,211,212,213,214,215,216,217,218,219,220,221,222].

The cumulative incidence of AVN is 3–10% at five years post-HCT [209, 223], and onset of AVN may range from six months to 10 years post-HCT [223]. Patients with a history of acute lymphoblastic leukemia or sickle cell disease may have AVN pre-HCT [224]. AVN most commonly affects the femoral head, although knees, ankles, elbows, vertebrae, and multiple concurrent joints may often be implicated [225]. AVN development is higher with females, more intensive conditioning regimens (especially TBI), moderate to severe cGVHD, prior acute GVHD, higher glucocorticoid exposures, and adolescent and young adults (AYA) where rapid bone growth occurs [222, 224,225,226,227,228,229].

Dermatologic complications

Cutaneous complications may occur in up to 70% of survivors [22] and is most commonly due to cGVHD but may also result from infections, subsequent neoplasms, or anti-infective and immunosuppressive drugs (Table 9, Supplementary Table 13). Excellent overviews of diagnosis and management of cutaneous cGVHD are available elsewhere [56, 79, 230,231,232], and the risk of skin cancers are reviewed below (see subsequent malignant neoplasms). Health care providers should recognize potential cutaneous side effects of glucocorticoids (easy bruising, loss of skin integrity) andcyclosporine (e.g. hirsutism, malignancy); they should monitor for cutaneous atrophy in survivors on high-potency topical glucocorticoids, and only recommend low-potency glucocorticoids (e.g. hydrocortisone 1–2.5%) in high-risk areas like the face [79, 231, 232].

Neurological and cognitive complications

Late neurologic dysfunction after HCT may affect the central nervous system (CNS) and peripheral nervous system, and are more frequent after allogeneic HCT (Table 10, Supplemental Table 14) [233,234,235]. Potential causes include infection or immunosuppression (CNI), neurotoxic chemotherapy (methotrexate, cytarabine, busulfan, thiotepa) and other medications, TA-TMA, cranial radiation or TBI, radiation-induced vasculitis, underlying disease (e.g. cerebrovascular disease, sickle cell disease, adenosine deaminase deficiency), CNS relapses of the original disease, PTLD, subsequent neoplasms (local effects or paraneoplastic syndromes) and, finally by exclusion, cGVHD [236].

Table 10 Neurological, cognitive complications, psychosocial health, and quality of life.

Survivors of TBI or cranial irradiation are at increased risk for secondary brain tumors (see subsequent malignant neoplasms). Radiation, cGVHD and glucocorticoid treatment are major risk factors for stroke [237,238,239,240,241]. For asymptomatic recipients of CNS radiation (particularly higher doses), brain MRI/ MRA screening for vasculitis maybe considered during shared decision-making but consensus on its utility is lacking [242]. Likewise, in recipients of high-dose neck radiation, carotid ultrasound screening can be considered during shared decision making.

Hearing loss secondary to radiation, platinum agents, and other drugs or complications may develop, and potentially lead to learning impairments [85, 243, 244]. Adenosine deaminase deficiency (ADA), osteopetrosis, lysosomal storage diseases and leukodystrophies are also associated with hearing disabilities.

Encephalopathy, aphasia, hemiparesis, seizures, apraxia, and tremors can happen in patients who have received intrathecal chemotherapy, cranial radiation, monoclonal antibodies, or tyrosine kinase inhibitors. Progressive multifocal leukoencephalopathy (PML) is causes by JC polyomavirus and has been associated with alemtuzumab, ATG, or rituximab therapy [245,246,247,248,249,250]. Opportunistic bacterial, toxoplasmosis, and viral infections (e.g. CMV, HHV-6) can lead to serious morbidity [251, 252]. Neurologic complications may impact cognitive function, affecting memory, concentration, speech and language skills, spatial abilities, and executive function [253,254,255,256]. Risk factors include female sex, younger age at HCT, extensive cGVHD, use of narcotics, glucocorticoids, antidepressants, sedatives, and TBI in children [12, 255]. Other potential risks include blinatumomab, intrathecal chemotherapy, PRES, TA-TMA, and history of immune effector cell-associated neurotoxicity syndrome (ICANS).

In addition to CNS complications, survivors less commonly develop immune mediated manifestations of peripheral nervous system, such as polymyositis, myasthenia gravis (see muscle and connective tissue complications) and chronic inflammatory demyelinating polyneuropathy, usually developing in association with tapering IST [257, 258, 204, 259,260,261]. Guillain-Barre-like syndrome with peripheral neuropathy and chronic demyelinating polyneuropathy related to GVHD have also been reported [262,263,264].

Psychosocial health and quality of life

Understanding patient perspectives on health related QOL is an integral part of survivorship care (Table 10, Supplemental Table 15). Physical function limitations can adversely affect a survivor’s ability to carry out daily tasks [12]. Approximately 10% of survivors report somatic distress >10 years post-HCT, with cGVHD, glucocorticoid exposure, and depression being risk-factors [12, 265, 266]. As many as 68% of patients report fatigue which is one of the most consistent symptoms negatively impacting QOL [267]. Risk factors for fatigue include female gender, cGVHD, younger age, and chronic pain [12, 268]. Similarly, up to half of survivors report sleep disturbance that does not seem to improve over time, and has been associated with female gender, older age, divorced status, unemployment, depression, distress, and autologous HCT [12]. Pain is reported among ~25% of survivors, often associated with musculoskeletal symptoms [12, 235, 266].

Anxiety and post-traumatic stress disorder (PTSD) affect 5–10% of long-term survivors [265, 269], whereas depression seems to gradually increase over time, affecting 10–30% [5, 270]. PTSD has been associated with GVHD and prolonged hospitalizations [269]. Anxiety has been associated with female gender, poor reported health status, lower household income, lower education, prednisone exposure and cGVHD [265, 270]. Depression is more frequent in male patients, those with poor functional status, lower household income, less education, TBI, prednisone exposure and cGVHD [265, 270, 271].

While lower social function scores have been reported in survivors compared to controls, others have reported excellent support from family and friends [253, 271, 272]. 60-80% of survivors are able to resume social roles, such as returning to work and school, but up to one third of survivors report worrying about being able to maintain employment [60, 271, 273,274,275,276,277,278,279,280]. Financial burden of HCT is a major concern for >20% of North American survivors and is relevant in other locations as well [253, 281,282,283,284]. AYAs seem to report lower social well-being and more difficulties establishing themselves in the labor market [278, 283, 285]. Pre-HCT lack of employment, less education, medical disability, late-effects, fatigue, pain, mental distress, GVHD, relapse and having a manual job have been associated with lower chances of post-HCT employment [60, 276, 278,279,280, 283, 285,286,287,288,289,290,291]. Financial difficulties are associated with worse physical and mental functioning, adverse medical outcome, and increased severity of GVHD [265, 288, 292,293,294].

There is no standard way of addressing perceived health status in HCT survivors, but many standardized patient-reported outcome questionnaires have been utilized, with accumulating evidence supporting the NIH-supported Patient-Reported Outcomes Measurement Information System (PROMIS) [295, 296]. Additionally, though not specifically validated in HCT, the NCCN distress thermometer can be used to triage patient concerns [297, 298]. For fatigue, NCCN survivorship guidelines may be helpful [298]. Sleep disorders can be investigated by detailed history and assessment of symptoms and potential interventions include review of medications, reviewing sleep/wake timing, physical activity, caffeine and other substance use and providing coping strategies such as relaxation and meditation techniques. For pain, appropriate mitigation strategies include non-pharmacologic interventions (e.g. massage, physical therapy, acupuncture) and/or analgesics, with non-opiates being prioritized [298]. Family members (including siblings) and informal caregivers can be even more affected by mental health issues than patients themselves, and their own QOL cannot be inferred from the patients’ results; referral to appropriate providers may be indicated [299,300,301,302].

It is essential for survivors to be able to rely on their standard support system, but also recognize they may get additional help from interacting with survivors who have similar experiences. Online peer mentor programs are available and presented in Appendix 2. Return to work programs can be instrumental, but practices vary widely Appendix 3 [303, 304]. Patients should be encouraged to evaluate their working/educational goals and identify barriers, working with human resources through their employer, occupational/vocational therapists, social workers and financial counselors [298].

Subsequent malignant neoplasms

HCT survivors have a 4–11 times increased risk of developing subsequent malignant neoplasms (SMN), compared with the general population [92, 305]. Among recipients of allogeneic HCT, the incidence of SMNs increases from 3.5% at 10 years to 12.8% at 15 years post-HCT [90, 93, 305]. SMNs can be categorized as hematologic (tMNs, PTLD) or solid tumors (Table 11, Supplementary Table 16).

Table 11 Subsequent malignant neoplasms.

Overall incidence of tMN is estimated to be 4% at 7 years post-HCT with a median occurrence at 2.5 years post-HCT [306]. Recipients of pre-HCT alkylating agents (particularly etoposide or cyclophosphamide), and possibly post-HCT cyclophosphamide, are at higher risk [307, 308]. Survivors have a higher risk of developing tMN after autologous HCT, but rarely, tMN can arise from donor hematopoiesis in patients who underwent allogeneic HCT [309, 310]. Patients conditioned with TBI, who received ≥3 lines of chemotherapy, who were poor stem cell mobilizers, or received lenalidomide maintenance for myeloma may have a higher risk of tMN [311,312,313,314]. The cumulative incidence of PTLD is 1% at 10 years after HCT and is associated with greater donor–recipient HLA disparity, T-cell depletion and GVHD [315]. Patients with primary immune deficiency are also at a higher risk of developing lymphomas. Recommendations on prevention and treatment of PTLD have been developed by the sixth European Conference on Infections in Leukemia and are described in detail elsewhere [316].

Incidence of solid cancers increases from approximately 2% at 10 years to 3–5% at 15 years post-HCT, varying widely based on exposures, family/ genetic history, age at and time since HCT [94, 317, 318]. Younger age at HCT, TBI, female sex, and cGVHD are risk factors for thyroid cancer in survivors [178, 319]. Survivors have a 7-16-fold higher risk for oral cancer compared to the general population; this risk is particularly increased in survivors with cGVHD and/or Fanconi anemia [89, 90, 93, 94, 320,321,322]. Genital cancer risks are also increased among recipients of reduced-intensity conditioning, limited field radiation, those with cGVHD and/or a diagnosis of Fanconi anemia [88, 90, 323]. Allogeneic HCT recipients are at an increased risk for gastrointestinal malignancies, with one report citing an standardized incidence ratio in survivors 5–10 years post-HCT of 74.0, 46.6 and 2.3 for cancer of the esophagus, oral cavity and colon, respectively [324]. Patients exposed to TBI are at risk of colorectal cancer and children exposed to TBI can develop polyps at an early age [143, 325]. Patients with inflammatory bowel disease are at very high risk of developing colon cancer, though it remains to be seen if similar issues occur in patients with gastrointestinal GVHD. Colonoscopy has been shown to be cost effective in those who received abdominal radiation exposure [142]. Recipients of chest irradiation (e.g. Hodgkin lymphoma) are at increased risk for breast cancer [326, 327]. Recipients of TBI without other radiation are also at increased risk [328]. Although rare, breast cancer in male childhood cancer survivors may be related to radiation therapy [329]. Anthracycline exposure, endogenous hormones and hormone replacement, and family history also should be considered when determining a patient’s overall risk [330, 331].

The 20-year post-HCT cumulative incidence is 6.5% for basal cell carcinoma and 3.4% for cutaneous squamous cell carcinoma [332]. The risk of melanoma is also significantly increased [333]. Areas of previously irradiated skin are most vulnerable to developing carcinomas, further exacerbated by a history of excessive sun exposure and chronic skin GVHD which itself can be triggered or aggravated by sun exposure. The role of immunosuppressive therapies in precipitating skin cancer is also a concern. Screening and prevention of skin malignancies mimics guidance offered for skin cGVHD (see dermatologic complications).

Survivors are also at higher risk for CNS tumors and sarcoma. Meningioma is the most frequent CNS tumor though more aggressive histologies may occur [334,335,336]. Heightened awareness for symptoms should be emphasized in patients after cranial irradiation or TBI. Survivors are at risk for secondary bone cancers, with a standardized incidence ratio of 8.5–13 [337, 338]. Risk factors may include underlying cancer predisposition syndromes (i.e., Li-Fraumeni syndrome, Diamond-Blackfan anemia) and radiation therapy. Clinicians should maintain a high level of suspicion in patients who present with relevant symtoms [338].

Special populations

Although there are many commonalities in risk factors and chronic health conditions for all HCT survivors, certain populations are more at risk for late-effects due to their underlying disease, treatment regimen or age-related late-effects and warrant long-term follow-up with multidisciplinary population-specific teams. Appendix 4 outlines considerations for special populations including hemoglobinopathies, marrow failure syndromes, inborn errors of immunity, enzymopathies, metabolic and other disorders, autoimmune disorders, myeloma, amyloidosis, infants, AYAs, and older adults (geriatric population). Appendix 5 provides a non-exhaustive list of additional references that may be helpful in managing late-effects of these specific populations. Specific recommendations for these populations can be found in the table within the corresponding organ system.

Models of survivorship care delivery

As survivorship care has become an integral part of cancer treatment, the Foundation for the Accreditation of Cellular Therapy and the Joint Accreditation Committee of International Society for Cell and Gene Therapy and EBMT (FACT-JACIE) guidelines mandate the monitoring and treatment of late-effects after HCT, including the transition from pediatric to adult care providers [339]. Besides survivorship care being recognized by many patients as a basic need [284, 335, 336], evidence for the added value of such practice is emerging. Indeed, those transplanted at centers with survivorship programs have improved survival [340]. However, in the United States, only 45% of programs have a HCT-specific long-term follow-up clinic [341]. Several different models of late effects follow-up have been proposed [4, 11, 341], however barriers to the establishment of survivorship clinics include lack of expertise, logistical challenges, and financial and reimbursement issues [341]. The implementation of programs and specific guidelines remains a challenge and ensuring survivors receive the recommended guidance is crucial [342,343,344].

Patients indicate a preference for holistic care, ideally with continued direct contact with the transplant center, particularly when they have developed GVHD, but this can be challenging when they live remote from their HCT team [284, 335, 336]. Survivorship care plans have been shown to decrease cancer-related distress and improve mental health in long-term survivors, although they do not exclusively replace comprehensive survivorship care [345]. Models using telehealth, mobile apps and wearable devices are currently being tested to overcome barriers [346,347,348,349,350]. However, technology use and uptake may be a challenge and patients often value human contact [284, 336, 351, 352]. In summary, a specific optimal survivorship care model has not been determined and different models continue to evolve based on HCT program and system strengths and abilities.

Future directions

As the transplantation and cellular therapy field continues to evolve and expand, so will the need for survivorship care. The long-term impact of novel small molecule cancer therapies and immunotherapies have not yet been well studied but have mechanisms of action that are generally distinct from conventional chemotherapy; some have idiosyncratic side effects, particularly relevant to specific populations (e.g. acute endocrine complications from certain immunotherapies) but long-term impacts are unclear [353]. Multiple CAR T-cell therapies are available and indications for these and additional cellular therapy products are quickly expanding. Cellular therapies may be associated with acute and subacute post-infusion complications mostly from altered immune function (e.g. cytokine release syndrome, ICANS) or from the elimination of cells expressing common antigens with the target cells (e.g. B-cell aplasia and CD19+ therapies) [76]. Gene therapies using an autologous-HCT platform have moved to late stage clinical trial testing, with some products now approved by regulatory agencies. Most clinical trial protocols require prolonged follow-up and are typically geared towards monitoring the underlying disease, specific genomic modification, and surveillance for clonal hematopoiesis/ tMN [354, 355]. While these trial mediated outcomes will provide crucial information for the long-term care of these patients, routine post-HCT care remains equally important (i.e. immune reconstitution and revaccination, monitoring for late-effects of conditioning chemotherapy). As many participants in these clinical trials have traveled great distances to enroll, often internationally, ensuring ongoing local follow-up and partnership with the research team is critical. Further, as these therapies become more established it will become increasingly important to provide data and encourage provider awareness of the long-term issues. All these novel approaches are likely to impact the range of late effects among future transplant and cellular therapy survivors, and further investigation is of the utmost importance.