Long-term progression-free survivors ("super responders") to olaparib maintenance in recurrent ovarian cancer: a multicenter real-world study (KCOG-G2101s).

BACKGROUND

PARP inhibitors have been shown to improve progression-free survival in patients with recurrent ovarian cancer. However, their potential for long-term response and cure remains unclear in real-world practice.

METHODS

We conducted a multicenter, retrospective study of patients with recurrent ovarian, fallopian tube, or peritoneal cancer who were treated with olaparib maintenance therapy in the Kansai Clinical Oncology Group. We analyzed clinical outcomes according to histological tissue type, platinum sensitivity, BRCA mutation status, and SLFN11 expression. Epithelial ovarian cancers were classified into type I (low-grade serous carcinoma, clear cell carcinoma, low-grade endometrioid carcinoma) and type II (high-grade serous carcinoma, high-grade endometrioid carcinoma and undifferentiated carcinoma).

RESULTS

A total of 72 patients were registered. The median progression-free survival and overall survival were 12.0 and 42.0 months, respectively. Type II tumors exhibited significantly longer progression-free survival than type I tumors (p = 0.027). Among type II tumors, those with platinum-sensitive recurrence and a response to chemotherapy (PSR-R, n = 51) had significantly better progression-free survival than non PSR-R (p < 0.0001). Notably, eight PSR-R patients (15.7%) achieved greater than five years of progression-free survival ("super responders"), and all had no evidence of disease at the last follow-up. BRCA mutations and SLFN11 expression were not associated with progression-free survival or super responders.

CONCLUSIONS

In this real-world cohort, a subset of patients with recurrent ovarian cancer achieved durable, potentially curative responses with olaparib maintenance, regardless of their BRCA mutation status. When evaluating PARP inhibitor therapy, long-term progression-free survival should be considered a key endpoint.