Introduction

Epithelioid sarcoma (ES) is a rare subtype of soft-tissue sarcoma of uncertain cellular origin that is characterized by failed expression of the SMARCB1/INI1 tumor-suppressor gene. This leads to the unopposed, constitutive, oncogenic activation of EZH2, an enzyme that trimethylates lysine 27 of histone H3 (H3K27me3) [1]. The rarity of ES in both pediatric and adult populations limits the available data on its natural history and treatment. SL Spunt, N Francotte, GL De Salvo, Y-Y Chi, I Zanetti, A Hayes–Jordan, SC Kao, D Orbach, B Brennan, AR Weiss, et al. [2] reviewed ES patients < 30 years old enrolled in two international prospective clinical trials and concluded that the estimated 5-year survival was 86.4%, 63.5%, and 0%, for low-, intermediate-, and high-risk patients, respectively. In addition, partial response was observed in 11/22 patients receiving neoadjuvant therapy (50%). Recently, M Gounder, P Schöffski, RL Jones, M Agulnik, GM Cote, VM Villalobos, S Attia, R Chugh, TW-W Chen, T Jahan, et al. [3] completed an international, open-label, phase-2 basket study and found that for locally advanced or metastatic ES, tazemetostat induced an objective response rate (ORR) of 15% (95% CI 7–26%). The median duration of response (DOR) was not reached at a median follow-up of 13.8 months (IQR 7.8–19.0). This suggests that in metastatic or advanced ES not eligible for complete resection, this epigenetic modifier is a good candidate for maintenance.

The backbone of standard treatment for localized ES is wide surgical excision, with radiation therapy utilized in cases at higher risk of local relapse [1]. However, systemic therapy should not be restricted to doxorubicin or tazemetostat alone in metastatic settings [1]. In some cases, alternative chemotherapy drugs or drug combinations may induce a more favorable response, which may be helpful in shrinking the tumor and improving surgical options. Patients may only cease taking medications when all of the residual tumors are eradicated via local treatment. In 2012, the earliest study on chemotherapy in epithelioid sarcoma had reported that systemic chemotherapy provided satisfactory palliation with a median progression-free survival (PFS) of 29 weeks (95% CI 23–35) [4]. Anthracycline-based regimens (usually doxorubicin in combination with ifosfamide) are commonly used as a first-line treatment. This treatment has been associated with an overall response rate ranging from 0 to 43% and a median progression-free survival (PFS) of three to eight months [5,6,7,8]. Gemcitabine, both as monotherapy or in combination with docetaxel, has a response rate in the range of 27–58% and a median PFS of 4–8 months [9, 10]. Signs of drug activity in a few cases have also been reported with pazopanib [11, 12] and dasatinib [13]. However, there is limited data on the activity of immunotherapy in ES, with one report of a response ascribed to pembrolizumab [14].

Irinotecan is a camptothecin analogue that was initially approved by the US Food and Drug Administration for the treatment of colorectal cancer in 1996 using a single, high-dose schedule [15]. This drug has taken on growing importance in the treatment of pediatric sarcomas, such as Ewing sarcoma and rhabdomyosarcoma, using a protracted administration schedule [16,17,18]. SN-38 is the active metabolite of irinotecan, and it mediates cytotoxicity by stabilizing the DNA topoisomerase I complex created during replication, preventing re-ligation of DNA, and restricting the activity of the topoisomerase I enzyme. In a preclinical study, we showed its efficacy in multiple soft tissue sarcomas [19,20,21], thus we tested this agent in combination with the anti-angiogenesis tyrosine kinase inhibitor (TKI) Anlotinib in refractory ES via off-label use.

In the current study, we retrospectively reviewed the records of patients treated with irinotecan, vincristine, and Anlotinib (VIA) with the following purposes: (1) to establish whether the VIA regimen is effective in metastatic or unresectable ES, including ORR and DOR and (2) to examine the tolerability of the VIA regimen in heavily treated patients with refractory metastatic or unresectable ES.

Methods

Eligibility

Data for the present analysis were retrospectively collected through the electronic medical record database of ES patients treated at Peking University People’s Hospital between July 2015–November 2021. Written informed consent was waived by the Medical Ethics Committee of Peking University People’s Hospital. The study met the requirements of the declaration of Helsinki and was carried out in accordance with the regulations of the local ethical committee.

Patients were selected according to the following criteria: (1) Grade 2 or 3 ES confirmed histologically using the American Joint Committee on Cancer (AJCC) system [22]; (2) patients presented with measurable lesions using the Response Evaluation Criteria In Solid Tumors (RECIST1.1) [23] and were not amenable to surgical resection or radiotherapy; (3) primary or secondary metastatic disease; (4) received more than two courses of the VIA regimen; (5) no concurrent treatment was given while on the VIA regimen; and (6) follow-up information and evaluation after chemotherapy were available.

Regimen

Treatment typically consisted of a 90-minute intravenous infusion of irinotecan at a dose of 50 mg/m2/d for 5 days every 3 weeks, vincristine given at a dose of 1.4 mg/m2 (maximum 2 mg) on days 1 and 8, and oral administration of Anlotinib once daily on days 1–14 within a 21-day cycle. This regimen had been previously tested in our IB trial for dose climbing [19, 20]. Routine radiographic evaluation was carried out once every 6 weeks, and the follow-up interval for patients ceasing treatment was generally every two months. Antiemetics were given three days before and after chemotherapy. Prophylactic therapies for diarrhea, such as antibiotics, probiotics, activated charcoal, or alkalinization, were routinely administrated due to our previous experience with this combination in Ewing sarcoma patients [19, 20]. Myeloid growth factor support between cycles was given when hematologic toxicity was observed.

Pathological evaluation and study parameters

Pathological reviews and SMARCB1 protein expression assays were performed in the Pathology Department of the Peking University People’s Hospital. Next-generation sequencing (NGS) was carried out by the Berry Oncology Corporation (Fuzhou, China). In addition to the data available in the database, surgical, reference pathology, radiology, and radiotherapy reports were studied by the first author. The regular protocol for patients with refractory sarcoma in our hospital consisted of baseline assessment via chest computed tomography (CT, with each layer ≤ 5 mm) and a bone scan or [18F]2-fluoro-2-deoxy-D-glucose-positron emission tomography (FDG-PET). If lesions other than lung metastases were identified, CT and/or magnetic resonance imaging (MRI) of those lesions was required. Clinical evaluation was assessed using the RECIST 1.1 criteria. PFS was analyzed using the Kaplan–Meier Method [24]. All of the statistical analyses were performed using SPSS 19.0 software (SPSS Inc., Chicago, IL, USA).

Results

Patient characteristics and demography

Between July 2015 and November 2021, a total of eight patients and 54 treatment courses were identified. The characteristics of the patients included in this study are summarized in Table 1. At initial diagnosis, the median age of all of the eligible patients was 36.0 years (range: 20.0–69.0 years). A female predominance (62.5%, 5/8) was noted in this cohort of patients. Among these patients, seven of eight (87.5%) had a primary lesion in the extremities while only one patient had multiple bone metastatic lesions with the primary lesion site unknown. No patient had primary lesions in the axial skeleton. The Eastern Cooperative Oncology Group (ECOG) score [25] was relatively low, with only one of eight patients (12.5%) having a score of more than two. Before receiving the combination therapy, two patients were treatment naïve, one had even progressed on first-line chemotherapy (doxorubicin and ifosfamide), four patients had progressed on two lines of systemic treatment (Table 2) consisting of various anti-angiogenesis TKIs, and one patient had progressed following more than three lines of therapy. Before VIA treatment, five of eight patients (62.5%) had localized inoperable lesions (local tumor thrombosis and lymphatic metastasis) and three of eight (37.5%) had metastatic lesions of the lung, bone, or liver. The presence of SMARCB1/INI1 protein expression and gene deletion occurred in seven of eight (87.5%) cases evaluated. Seven of these patients were classified as classic-type ES and one was deemed proximal-type ES [1].

Table 1 Patients demographics
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Table 2 Detailed information and treatment courses for each patient
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Efficacy

Based on RECIST1.1 criteria, three of eight (37.5%) patients experienced a partial response (PR) while five of eight (62.5%) had stable disease (SD) (Figs. 1 and 2) [23]. The DOR was 2.9, 7.2, and 8.3 months in the three patients, with two patients stopping treatment due to adverse events (AEs). The one patient is currently using the combination therapy for clinical benefit and is tolerating it well (Figs. 3 and 4). None of the patients experienced Progression of Disease (PD) or had ever progressed on this treatment combination. All of the patients who were disease stable ceased treatment due to reasons other than progression. Due to many difficulties (AEs, patient’s intention, local therapy, and COVID-19 pandemic control) and the small sample size in this case series, PFS could not be calculated by the Kaplan–Meier Method. However, with a follow-up time ranging from 9.5 to 86.3 months, we were able to determine that the median Overall Survival (OS) was 21.3 (95% CI, 54.1, 95.4) months and the 5-year OS rate was 83.3% (standard error 15.2%) (Fig. 5).

Fig. 1
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An epithelioid sarcoma patient with primary lesion located at right finger (patient number 4 in table 2) developed lymphatic metastasis to right axillary fossa before the combination therapy of irinotecan, vincristine and anlotinib

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Fig. 2
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Partial Response was noticed shortly after 3 cycles of this combination therapy in the right axillary fossa lymph node metastasis (patient number 4 in Table 2)

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Fig. 3
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Manifestation of coronal scan of magnetic resonance imaging for the patient with right axillary fossa lymphatic metastasis before this combination treatment, who has progressed upon two lines of chemotherapy

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Fig. 4
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The magnetic resonance imaging manifestation after 3 cycles of irinotecan, vincristine and anlotinib, which induced shrink of the tumor as well as liquefactive necrosis

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Fig. 5
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The Kaplan-meier estimate survival curve for overall survival in this group of patients from diagnosis to death

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Toxicity

All of the AEs related to the therapy were routinely recorded in the electronic medical record using Common Terminology Criteria for Adverse Events (CTCAE) (version 5.0) [26]. Grade 3–4 AEs are summarized in Table 3. The most common Grade 3 or 4 AEs included myelosuppression (92.6%) (particularly neutropenia and anemia), diarrhea (81.5%), and nausea and vomiting (68.6%). Notably, one patient experienced pelvic soft tissue necrosis and rupture (partially tumor-related and partially treatment-related), which required surgery for drainage (Figs. 6 and 7). Following debridement and suturing, this female patient recovered from the infection and continued using single chemotherapy treatment with irinotecan (patient number 5 in Table 2). However, bladder perforation occurred shortly after this due to previous radiation and tumor rupture, which required a second surgery for debridement and uretero-cutaneous diversion. One patient with a large left inguinal fold mass (patient 7 in Table 2) had grade 4 diarrhea and dehydration leading to loss of consciousness and was admitted directly to the intensive care unit (ICU) for palliative treatment. This suggests that the combination treatment should be accompanied with appropriate preventive measures to avoid severe toxicities.

Table 3 Grade 3 and 4 Toxicities observed in 8 patients (54 courses) according to CTCAE 5.0
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Fig. 6
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A female patients (patient number 5 in Table 2) with epithelioid sarcoma in right inguinal fold experienced tumor rupture in her retroperitoneum. This was her computerized tomography (CT) scan before rupture

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Fig. 7
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The CT scan taken shortly after her tumor rupture in her retroperitoneum with drainage tube after Emergent debridement surgery (patient number 5 in Table 2). Following debridement and suturing, this female patient recovered from the infection and continued using single chemotherapy of irinotecan

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Discussion

The present study, which had an ORR of 37.5%, provides evidence for the use of an alternative systemic treatment option for refractory ES. In indolent, locally aggressive, ultra-rare soft-tissue sarcomas, systemic treatment focused on ORR may effectively reduce tumor load. This, in turn, may convert inoperable ES to an operable state and allow late focal stage patients to avoid drug therapy and remain disease-free. The rationale for the combination of irinotecan, vinsristine, and Anlotinib in the present study was based on the theory that the addition of chemotherapy to TKIs may overcome the cytostatic properties of molecular targeted agents, especially with regard to anti-angiogenesis drugs [27]. The success of the LEADER study [28], studies reporting Lenvatinib used with etoposide plus ifosfamide in osteosarcoma [27], and other similar combinations [29] led us to test other cytotoxic agents commonly used in pediatric sarcoma patients in combination with Anlotinib. Anlotinib was used because it was deemed to be less toxic in a previous trial and is therefore more suitable for combination therapy [30, 31]. Tazemetostat was not used in these advanced patients because the agent had not yet been approved for application in mainland China when the patients were treated (2015–2021). There were no better systemic options for ES patients that had progressed on anthracycline-based chemotherapy regimens or TKIs.

Based on the results of a nonrandomized Phase II study (EZH-202; ClinicalTrials.gov: NCT02601950) that included INI1 negative advanced ES, the US FDA granted accelerated approval for tazemetostat (Tazverik R; Epizyme, Inc., 400 Technology Square, MA, USA) for the treatment of adult advanced ES in January 2020. This is a first-in-class, oral, small-molecule selective inhibitor of EZH2 and was also the first epigenetic regulating agent approved for soft tissue sarcoma [3]. Studies of epigenetic agents have become an important research focus as this is another tumor regulatory mechanism in tumor pathogenesis. However, the efficacy of EZH2 was subtle in clinical trials of its use in other sarcomas, especially when used as a single-agent therapy [32, 33]. In ES, we found an ORR of 15% in the modified intention-to-treat analysis, with durable responses and a median progression-free survival of 5.5 months [3]. In addition, most treatment-induced AEs were mild and tolerable [27], which suggests that this drug might be more suitable for maintenance in high-risk ES. It should be noted that a report by SL Spunt, N Francotte, GL De Salvo, Y-Y Chi, I Zanetti, A Hayes–Jordan, SC Kao, D Orbach, B Brennan, AR Weiss, et al. [2] showed that 71.3% of ES patients who experienced full resection of all tumor lesions achieved 5-year event-free survival (95% CI, 56.7.0–81.7). Thus, ORR is important in ES as it may allow patients to undergo wide resection or radiotherapy. We have summarized the most promising, recent systemic treatments for ES in Table 4. We noted that chemotherapies such as doxorubicin, ifosfamide, gemcitabine, docetaxel or these agents in combination, can induce greater ORR and should be considered more in neoadjuvant settings.

Table 4 Summary of systemic studies in epithelioid sarcoma
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Nevertheless, this study investigated an alternative systemic treatment option with a predilection to more toxic profiles compared to previous studies [3, 13]. Diarrhea, nausea and vomiting, and myelosuppression were found to be severe. Therefore, prophylactic therapy should always be administrated to avoid these unexpected consequences [20]. Even when full tumor removal is achieved, physicians should remain vigilant for tumor rupture or visceral perforation, partly due to the effects of TKIs [34, 35]. In addition, single chemotherapy with irinotecan should be considered later in clinical practice to assess its efficacy and toxicity.

This study had several limitations. First, this was a retrospective study with a small sample size, making statistical calculations difficult. Thus, we could only present each case in detail in Table 2 to demonstrate the results. Second, most patients ceased the treatment for various reasons other than progression, leading to a lack of PFS data. Thus, PFS was not investigated in this study. As a result, we focused on the VIA regimen and its ORR, which is not adequate to address the activity of the regimen. Third, this cohort of patients was generally heavily treated with various modalities including surgery, radiation, and other biological agents, making interpretation of the data difficult. To guarantee the uniformity of the data, the inclusion criteria were retrospectively designed and rigidly implemented, leading to the small sample size.

Conclusions

We explored a novel treatment regimen for ES patients (a combination of irinotecan, vincristine, and Anlotinib) used in our past clinical practice. This treatment regimen resulted in relatively high response rates. Special attention should be paid to its toxicities, which were in accordance and comparable with similar combinations. Further investigation using prospective trials should be carried out to complement these findings.