Dismal prognosis of Pneumocystis jirovecii pneumonia in patients with multiple myeloma

Patients with multiple myeloma (MM) are at high risk for infections, including opportunistic infections such as Pneumocystis jirovecii pneumonia (PJP). We conducted a retrospective analysis of patients with MM developing PJP over a 6-year period between January 2016 and December 2021 at the University Hospital of Würzburg by screening cases of microbiologically documented PJP. A total of 201 positive results for P. jirovecii in respiratory specimens were retrospectively retrieved through our microbiology database. Of these cases, 13 patients with MM fulfilled the definition of probable PJP according to EORTC fungal disease definitions. We observed two peaks in PJP incidence, one after stem cell transplantation during first-line treatment (n = 5) and the other in heavily pretreated patients with six or more prior lines of therapy (n = 6). There was high morbidity with nine (69%) patients admitted to the ICU, seven of whom (78%) required mechanical ventilation, and high mortality (62%, n = 8). Notably, only two of the 13 patients (15%) had received PJP prophylaxis. The main reason for discontinuation of prophylaxis with trimethoprim-sulfamethoxazole was grade IV neutropenia. The observed morbidity and mortality of PJP in MM patients are significant and even higher than reported for patients with other hematologic malignancies. According to most current guidelines, the use of prophylaxis would have been clearly recommended in no more than three (23%) of the 13 patients. This illustrates the need to critically reconsider the indications for PJP prophylaxis, which remain incompletely defined.


Introduction
Immune dysfunction and related infectious complications are a hallmark of multiple myeloma (MM), the second most common hematologic malignancy.Both cellular and humoral immune responses are compromised by the disease itself [1] but also by its treatment, leaving MM patients susceptible to all types of infections, including those caused by opportunistic pathogens [2].
A serious and often fatal opportunistic infection in immunocompromised hosts is Pneumocystis jirovecii pneumonia (PJP).Currently, the incidence of PJP is decreasing in HIVpositive patients, but increasing in HIV-negative patients, who experience a more aggressive disease course with a higher need for intensive care treatment and a higher proportion of fatal outcomes [3][4][5].Diagnosis of PJP is based on host factors and typical clinical, radiological, and microbial findings.According to the EORTC criteria, the diagnosis of proven PJP requires the presence of clinical and radiological criteria and microscopic demonstration of P. jirovecii in respiratory specimens or tissue [6].Probable PJP is based on the presence of appropriate host factors, clinical and radiological criteria, amplification of P. jirovecii DNA in respiratory specimens, and/or detection of β-D-glucan in serum [6].
Trimethoprim/sulfamethoxazole (TMP-SMX) is the treatment of choice for PJP, alternative options include atovaquone, pentamidine, and clindamycin-primaquine [3,7].For the prevention of PJ disease, current ASCO, ECIL, and national guidelines explicitly recommend PJP prophylaxis only in hematologic patients at high risk, such as those following allogeneic transplantation, those diagnosed with acute lymphoblastic leukemia, or those receiving high-dose corticosteroids or certain lymphodepleting agents [7][8][9][10].However, some MM-specific guidelines also clearly recommend PJP prophylaxis in patients following autologous hematopoietic stem cell transplantation (HSCT) [11,12], which is also the standard of care at our institution.
To our knowledge, PJP has yet to be analyzed systematically in patients with MM.This becomes even more important as novel treatment options such as CAR-T-cell therapies and bispecific antibodies put more patients at risk for opportunistic infections like PJP.In studies with BCMA-directed bispecific antibodies, a significant proportion (3.6-4.9%) of patients developed PJP [13].Therefore, we retrospectively collected all cases of PJP in myeloma patients from 2016 to 2021 at our institution, a tertiary care hospital, and evaluated patient characteristics, diagnostic findings, disease course and outcome, and the use of PJP prophylaxis as a quality improvement project in collaboration between the in-house antimicrobial stewardship team (AMS) and the hematology department.

Methods
All cases of microbiologically documented PJP (positive immune staining and/or positive RT-PCR) in respiratory specimens were retrospectively collected between January 2016 and December 2021 through our microbiology database and screened for patients with a diagnosis of MM.The clinical history of MM patients was then retrieved.
Diagnoses of probable and proven PJP were assessed according to EORTC/MSGERC invasive fungal disease definitions in individuals without HIV [6].As β-D-glucan testing was not available during the entire study period, it was not considered in the diagnosis of additional cases with probable PJP.Quantitative PCR thresholds for distinguishing between colonization and infection with P. jirovecii have not yet been established, so PCR thresholds were not used in this analysis.

Patient characteristics
To identify patients with MM and PJP, we reviewed 201 cases with positive tests for P. jirovecii in respiratory specimens through our microbiology database.Nine of these 201 cases showed a positive microscopy for P. jirovecii; the remaining 192 cases had been tested positive by qPCR.Thirteen patients with a diagnosis of MM, all with positive qPCR and typical clinical and radiological criteria, met the criteria for probable PJP according to the EORTC guidelines [6].The median age at diagnosis of PJP was 60 years.Thirtyeight percent of patients were male.
We observed two peaks of PJP incidence, one after HSCT during first-line treatment (n = 5, 38%) and the other in heavily pretreated patients with six or more prior lines of therapy (n = 6, 46%).Patient characteristics, diagnostic findings, treatment, and outcome are shown in Table 1.Patients had a median history of multiple myeloma diagnosis of 5.8 years.Six (46%) patients had received corticosteroids in the 4 weeks preceding the diagnosis of PJP with a median dosage of 13 mg prednisolone/day.A total of four patients had undergone prior allogeneic transplantation, two as part of a primary tandem autologous-allogeneic transplantation strategy and two as a salvage therapy for refractory disease.

Diagnostic findings, disease course, and outcome
PJP is a diagnostic challenge.All but one patient had elevated LDH with a median of 351 U/l.Four patients had a known CD4+ T cell count, all below 200 /μL with a range of 19 to 131 /μL.Chest CT scans of all patients showed typical radiological findings such as ground glass opacities (GGO) in all but one patient (92%) and/or additional consolidations in 10 patients (77%) as a sign of a higher grade of inflammation.qPCR Ct values ranged from 18.4 to 32.
Antimicrobial treatment for P. jirovecii was given to 12 out of 13 patients.The patient who was not treated for PJP deteriorated rapidly and was diagnosed with PJP post mortem.Ten out of 13 patients (77%) were treated primarily with high-dose TMP-SMX according to the standard of care [3].One patient, in whom PJP was diagnosed during grade IV neutropenia following high-dose chemotherapy, was first treated with atovaquone and switched to TMP-SMX after stable engraftment.One other patient was treated with clindamycin/caspofungin. Adjunctive steroids were used in 8 out of 13 patients (62%).
Nine of the 13 patients (69%) were admitted to the ICU, two of them underwent non-invasive ventilation with high-flow oxygen and seven of nine patients (78%) required mechanical ventilation.Duration of mechanical ventilation ranged between 1 and 10 days.Eight of the 13 patients (62%) died, seven of them due to respiratory failure.The other patient showed altered mental status and seizures of unresolved etiology.The patients with a fatal outcome had a longer history of MM, were more heavily pretreated, and showed higher baseline LDH levels (Table 1).Three of them also had parallel reactivation of HSV and/or CMV (Table 1).Only one of the patients surviving

Use of prophylaxis
A key question is whether prophylaxis was used in the MM patients who acquired PJP.Remarkably, only two (13%) patients were on a PJP prophylaxis, one on TMP-SMX and the other on atovaquone.According to most national and international guidelines [8-10], prophylaxis would have been strictly indicated in only three (23%) of the 13 patients.One of them was the patient receiving atovaquone, the second patient developed PJP before the planned pentamidine prophylaxis could be started, and in the third patient, TMP-SMX had been interrupted for fear of prolonging chemotherapy-induced neutropenia.TMP-SMX had also been discontinued in two other patients with grade IV neutropenia following high-dose chemotherapy at least 3 weeks prior to diagnosis of PJP.In summary, neutropenia turned out to be an important factor in clinical decision-making regarding the discontinuation of prophylaxis in our study.

Discussion
This retrospective study analyzes Pneumocystis jirovecii pneumonia in patients with MM in a single center over the course of 6 years.To date, there are very few case reports of up to three patients dedicated to PJP in MM [2,[14][15][16].In our patient population, PJP mainly affected MM patients on their first line of therapy after HSCT and heavily pretreated patients with six or more prior lines of therapy.One possible explanation might be that a low CD4+ cell count is a risk factor for PJP even in HIV-negative patients [17] and that CD4+ cell counts decrease with each line of myeloma therapy [2].The observed two incidence peaks in early and late disease stages are therefore likely to represent the time points when physicians treating MM patients ought to be particularly aware of the occurrence of opportunistic infections like PJP.We observed very poor outcomes in MM patients with a high ICU admission rate of 69% of patients, 78% of them requiring mechanical ventilation.Other studies have shown lower ICU admission rates of 42% for patients with hematologic malignancy [18].Reported ICU admission rates for HIV-negative patients range from 38 to 52%, with 71% of them requiring mechanical ventilation [19,20].A rate of 43% of allogeneic transplant recipients who develop PJP has been reported to require mechanical ventilation [4].Around two-thirds of our MM patients died within 4 weeks after PJP diagnosis or due to PJP-related complications.In the literature, PJP-related deaths have been reported in 43-48% of patients undergoing HSCT (autologous and allogeneic) [4,21], in 29% of patients with hematologic malignancy in general [18], and in 15-30% of HIV-negative patients [4,22,23].In summary, morbidity and mortality in MM patients were higher than reported for hematologic patients and HIV-negative patients.
The key question arising from this is what prophylactic measures are adequate to prevent the occurrence of potentially fatal PJP in MM patients.The use of TMP-SMX prophylaxis has been generally shown to be effective in reducing the risk of PJP by 85% [24].Most MM patients in this analysis (77%, n = 10) did not have an indication for PJP prophylaxis according to most current national and international guidelines [8][9][10], recommending primary PJP prophylaxis in adult patients with high risk for PJP only.In all other settings, the use of PJP prophylaxis remains an individual decision, also due to a lack of prospective data in HIV-negative patients.Contrary to the aforementioned guidelines, the use of PJP prophylaxis in MM patients undergoing HSCT is recommended by MM-specific guidelines [11,12] and practiced at many institutions, including ours.Our study also exemplifies fatal outcomes in which PJP prophylaxis was interrupted due to grade IV neutropenia.There are insufficient data regarding a possible prolongation of neutropenia with the prophylactic use of TMP-SMX; in a Cochrane analysis comparing studies on the use of PJP prophylaxis, there was no significant difference in adverse events between patients receiving TMP-SMX or placebo [24].
To conclude, PJP is a rare but potentially fatal complication in MM.Indications for PJP prophylaxis are still incompletely defined, resulting in inconsistent approaches.Discontinuation of PJP prophylaxis in neutropenic patients appears to be outcome-determining and needs to be critically reconsidered.Given the high morbidity and mortality of PJP in patients with MM in our analysis, indication for PJP prophylaxis should be re-evaluated at least in this subcohort, going along with new emerging treatments such as CAR-Tcells and bispecific antibodies.More randomized controlled trials are required to pave a different approach to prevent PJP.
Author contribution All authors contributed to the study conception and design.Material preparation, data collection, and analysis were performed by CR, GS, and LR.The first draft of the manuscript was written by CR, GS, and LR and all authors commented on previous versions of the manuscript.All authors read and approved the final manuscript.
Funding Open Access funding enabled and organized by Projekt DEAL.
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Table 1
Patient characteristics, key diagnostic findings, outcome, and use of PJP prophylaxis