Remarkable Response to the Triplet Combination of Olaparib with Pembrolizumab and Bevacizumab in the Third-Line Treatment of an Ovarian Clear Cell Carcinoma Patient with an ARID1A Mutation: A Case Report

Aberrant SWI/SNF Complex Members Are Predominant in Rare Ovarian Malignancies-Therapeutic Vulnerabilities in Treatment-Resistant Subtypes

SWI/SNF (SWItch/Sucrose Non-Fermentable) is the most frequently mutated chromatin-remodelling complex in human malignancy, with over 20% of tumours having a mutation in a SWI/SNF complex member. Mutations in specific SWI/SNF complex members are characteristic of rare chemoresistant ovarian cancer histopathological subtypes. Somatic mutations in ARID1A, encoding one of the mutually exclusive DNA-binding subunits of SWI/SNF, occur in 42-67% of ovarian clear cell carcinomas (OCCC). The concomitant somatic or germline mutation and epigenetic silencing of the mutually exclusive ATPase subunits SMARCA4 and SMARCA2, respectively, occurs in Small cell carcinoma of the ovary, hypercalcaemic type (SCCOHT), with SMARCA4 mutation reported in 69-100% of SCCOHT cases and SMARCA2 silencing seen 86-100% of the time. Somatic ARID1A mutations also occur in endometrioid ovarian cancer (EnOC), as well as in the chronic benign condition endometriosis, possibly as precursors to the development of the endometriosis-associated cancers OCCC and EnOC. Mutation of the ARID1A paralogue ARID1B can also occur in both OCCC and SCCOHT. Mutations in other SWI/SNF complex members, including SMARCA2, SMARCB1 and SMARCC1, occur rarely in either OCCC or SCCOHT. Abrogated SWI/SNF raises opportunities for pharmacological inhibition, including the use of DNA damage repair inhibitors, kinase and epigenetic inhibitors, as well as immune checkpoint blockade.

Pembrolizumab with bevacizumab and cyclophosphamide for the treatment of recurrent ovarian clear cell carcinoma: A case series

Introduction

Treatment for recurrent ovarian clear cell carcinoma (OCCC) is clinically challenging as response rates to traditional chemotherapy are low, and recurrence rates are high. Immunotherapy has shown promise for this ovarian cancer (OC) subtype, and tumor molecular testing allows for the identification of a patient population that might benefit most from this treatment. We describe the clinical course and somatic genomic testing of 4 patients who received pembrolizumab for recurrent OCCC concurrent with a combination of bevacizumab and/or cyclophosphamide.

Methods

All patients with OCCC treated with immune checkpoint inhibitors (ICI) within a single health system between 2018 and 2023 (excluding those on clinical trials) were identified via retrospective chart review.

Results

Four patients were included. The average age at diagnosis was 56.5 years, and the number of prior treatments ranged from 1 to 6. All patients received pembrolizumab combined with either bevacizumab and/or cyclophosphamide. All patients (n = 3) who received pembrolizumab and bevacizumab experienced a partial response. Responses were durable, ranging from 6 to 15 months. Somatic genomic testing results demonstrated microsatellite stability and low tumor mutational burden in all patient tumors, and 3 had AT-Rich Interaction Domain 1A gene (ARID1A) mutations. Notably, two patients had treatment-limiting toxicities, one with presumed immune-mediated grade 2 myocarditis, and another with grade 5 hepatitis.

Conclusions

Pembrolizumab, combined with bevacizumab and cyclophosphamide, is a promising treatment option for patients with recurrent OCCC, though careful risk assessment and counseling regarding toxicities is necessary to maximize the safety and efficacy of this treatment regimen. Prospective studies are needed for validation.