Survival impact of extended cycles of second-line chemotherapy in platinum-sensitive relapsed ovarian cancer patients with residual tumor after six cycles

Background: To determine if extended chemotherapy improves survival outcomes in patients with platinum-sensitive relapsed epithelial ovarian cancer (EOC) who have residual disease after six cycles of second-line chemotherapy. Methods: In this study, 135 EOC patients who experienced platinum-sensitive recurrence after primary treatment between 2008 and 2018, and had a residual tumor ≥0.5 cm (detected on CT scans) after completing six cycles of second-line, platinum-based chemotherapy, were retrospectively reviewed. Based on the number of main therapy cycles (second-line chemotherapy), we divided patients into an extended group (>6 cycles, n = 52) or a standard group (6 cycles, n = 83) and compared patient characteristics and survival outcomes between these groups. Results: The extended group had a shorter platinum-free interval after primary treatment than the standard group (median, 11.0 vs. 13.1 months; P = 0.018). Secondary debulking surgery was less frequently performed in the standard group (1.9% vs. 19.3%; P = 0.003). After six chemotherapy cycles, the extended and standard groups showed similar serum CA-125 levels (P = 0.122) and residual tumor sizes (P = 0.232). There was no difference in overall survival (OS) between the groups (P = 0.382), although the extended group had significantly worse progression-free survival (PFS) than the standard group (median, 13.9 vs. 15.1 months; P = 0.012). Multivariate analyses revealed that platinum-free interval was an independent prognostic factor for PFS and OS, but extended chemotherapy was not (PFS: HR, 1.25; 95% CI, 0.84–1.85; P = 0.279; and OS: HR, 1.36; 95% CI, 0.72–2.56; P = 0.342). We observed consistent results in the subset of patients who did not undergo secondary debulking surgery. Conclusions: More than six cycles of platinum-based chemotherapy might not improve survival outcomes in patients with platinum-sensitive recurrent EOC who had a residual tumor ≥0.5 cm after six cycles of second-line chemotherapy.