Genetic Landscape in Women with Metastatic Ovarian Cancer Before and During Treatment with PARP Inhibitors

Therapy related acute myeloid leukemia and myelodysplasia (t-MN) is a potential late complication of cytotoxic therapy, and it is of particular concern in the treatment of patients with epithelial ovarian carcinoma (EOC) exposed to multiple cycles of platinum-based chemotherapy during the course of their disease. An epidemiological analysis published in 2011 (Gynecologic Oncology) showed that the overall incidence of t-AML is 0.17%, with a median latency to development of leukemia of 4 years (range 0-27 years). Inhibition of PARP is a potential synthetic lethal therapeutic strategy for the treatment of cancers characterized by specific DNA repair defects, such as those that harbor a BRCA1 or BRCA2 (BRCA1/2) mutation and are therefore deficient in homologous recombination repair. In homologous recombination-deficient tumors, PARP inhibition eliminates an alternative DNA repair pathway essential for maintaining viability, leading to tumor cell death. The estimated prevalence of BRCA1/2 mutations in V2 03/06/2021 2 patients with newly diagnosed high-grade serous ovarian cancer is 20-25% and it might be higher in patients with platinum-sensitive, relapsed ovarian cancer. Early studies have shown significant efficacy for PARP inhibitors in patients with germline BRCA1/2 mutations. Our hypothesis is that these patients are carriers of clonal hematopoiesis of indeterminate potential (CHIP) before treatment with PARPi. CHIP refers to the presence of clonal population(s) of hematopoietic cells with somatic mutations in genes associated with hematological malignancies (e.g. DNMT3A, ASXL1, TET2, TP53 and others), in the absence of morphological evidence of disease. The proposed study will address the hypothesis that platinum-based chemotherapy may promote the onset of newly developed mutated clones and clonal selection of hematopoietic stem cells harboring somatic mutations. Moreover, the concomitant presence of germline mutations in cancer predisposing genes might increase the pool of pre-existing hematopoietic clones and/or favor the accumulation of subsequent somatic mutations. In this context, the inhibition of PARP-mediated repair of DNA lesions created by chemo or radiotherapy can further favor t-MN development.