Introduction/Background The standard of care for advanced epithelial ovarian cancer (EAOC) is primary debulking surgery (PDS) followed by platinum-based chemotherapy and maintenance treatment. If optimal cytoreduction is not achievable, 3–4 cycles of neoadjuvant chemotherapy (NACT) followed by interval debulking surgery (IDS) are recommended. The impact on outcomes of delayed IDS (IDS-D) after 6 cycles remains debated.

This study aims to assess the real-life impact of surgical timing, medical treatment and their combination on disease free survival (DFS) and relapse pattern in EAOC patients.

Methodology EAOC patients who underwent PDS, IDS, or IDS-D from January 2012 to December 2022 were identified from the institutional database. The Cox regression model was used to compare DFS and adjusted for confounding factors provided by inverse probability of treatment weighting propensity score (IPTW) based on age, performance status and stage, collected retrospectively. The pattern of recurrence was also evaluated according to surgical timing, chemotherapy and maintenance treatment.

Results Of 226 EAOC-included patients, 116 (51.6%) underwent PDS, 61 (27.1%) IDS and 48 (21.3%) IDS-D. After a median follow-up of 40 months, DFS was 24.2 months in PDS, 17.4 months in IDS (HR=1.5; CI 95% [0.9 -2.2]) and 17.5 months in IDS-D (HR=1.1; CI 95% [0.7–1.8]) from IPTW analysis. The absence of residual disease was the only prognostic factor (HR=1.8; CI 95% [1.2–2.6], p=0.001).

Sites of recurrences were identified as follows: 21 (14.4%) in lymph nodes, 14 (9.6%) isolated peritoneal with or without lymph nodes, 57 (39.0%) diffuse peritoneal without parenchymal involvement, 26 (17.8%) in liver and spleen parenchyma, 28 (19.2%) extra-abdominal. Timing of surgery and medical treatment do not affect the pattern of recurrence (lymph nodes + single peritoneal vs diffuse peritoneal + epatic + extra-abdominal p=0.27).

Conclusion In our series IDS or IDS-D do not impact DFS. Timing of surgery and medical treatment do not affect relapse pattern.

Disclosures The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper. No specific funding was obtained for this study.