Comparison of Second-Line Chemotherapies for First-Relapsed High-Grade Serous Ovarian Cancer: A Retrospective Study

Background/Objectives: To compare oncologic outcomes of second-line chemotherapy regimens in relapsed high-grade serous ovarian cancer (HGSOC) by platinum sensitivity. Methods: We retrospectively reviewed HGSOC patients treated at two centers (June 2003–December 2020), classified by platinum-free interval (6- and 12-month cut-offs). Outcomes were progression-free survival (PFS, primary) and objective response and disease control rates (secondary). Regimens administered to ≥10% of patients or with favorable outcomes were compared using multivariable Cox analyses. Results: Among 468 patients (41.2% sensitive, 32.9% partially sensitive, 25.9% resistant), platinum-sensitive patients were younger (p = 0.024), diagnosed earlier, and more likely to undergo primary debulking surgery (both p < 0.001), achieving best outcomes after second-line chemotherapy (median PFS 14.8 vs. 10.5 and 5.2 months, p < 0.001). In both sensitive groups, the most common regimens were taxane + platinum ± bevacizumab, followed by pegylated liposomal doxorubicin + carboplatin, which was associated with shorter PFS in platinum-sensitive patients (hazard ratio (HR) 1.67, p = 0.016). Second-line maintenance with bevacizumab or poly(ADP-ribose) polymerase inhibitors was associated with improved PFS in both groups (p < 0.001). In platinum-resistant patients, the omission of bevacizumab (HR 2.01, p < 0.001) and a primary treatment history without cytoreduction (HR 4.43, p = 0.044) were associated with inferior outcomes. Conclusions: In platinum-sensitive patients with a favorable prognosis, taxane + platinum regimens were most commonly used and outperformed PLD + carboplatin. Maintenance therapy also conferred a meaningful benefit. In platinum-resistant disease, bevacizumab use and prior cytoreductive surgery may improve outcomes, underscoring the importance of treatment selection and surgical approach.