Cumulative cytotoxic chemotherapy exposure after the introduction of PARP inhibitors in advanced high-grade serous tubo-ovarian and primary peritoneal carcinoma: A descriptive single-center historical cohort study.

The present study aimed to describe real-world treatment patterns, cumulative exposure to cytotoxic chemotherapy, and exploratory survival outcomes before and after the clinical introduction of poly(ADP-ribose) polymerase (PARP) inhibitors in patients with stage III-IV high-grade serous ovarian, fallopian tube or primary peritoneal carcinoma. The medical records of patients with stage III-IV high-grade serous ovarian, fallopian tube or primary peritoneal carcinoma who received chemotherapy at Jichi Medical University Saitama Medical Center (Saitama, Japan) between January 2009 and August 2023 were retrospectively reviewed. The primary outcomes were the number of chemotherapy regimens and the cumulative number of cytotoxic chemotherapy cycles. Overall survival was evaluated as an exploratory secondary outcome. The final cohort included 86 patients, comprising 48 patients in the PARP inhibitor-untreated group and 38 patients in the PARP inhibitor-treated group. The groups exhibited differences in several baseline characteristics, including International Federation of Gynecology and Obstetrics stage, receipt of neoadjuvant chemotherapy and cytoreduction status. The cumulative number of cytotoxic chemotherapy cycles was significantly higher in the PARP inhibitor-untreated group than in the PARP inhibitor-treated group [median, 18.5 (range, 6-49) vs. 12.0 (range, 5-45); P=0.020], whereas the number of chemotherapy regimens did not differ significantly [median, 3 (range, 1-7) vs. 2 (range, 1-8); P=0.081]. Overall survival appeared to be longer in the PARP inhibitor-treated group; however, this finding should be interpreted with caution due to the retrospective historical design and baseline imbalances. In this descriptive single-center cohort restricted to advanced high-grade serous ovarian, fallopian tube or primary peritoneal carcinoma, the clinical introduction of PARP inhibitors was associated with lower cumulative exposure to cytotoxic chemotherapy. No causal inference regarding survival benefits could be made due to substantial treatment-selection bias and baseline imbalances.