Objective: Treatment for advanced epithelial ovarian cancer (EOC) consists of debulking surgery and (neo)adjuvant platinum-based chemotherapy. The aim of this study was to evaluate whether the time from surgery to adjuvant chemotherapy (TTC) was associated with clinical outcome.

Methods: We identified all Dutch patients who received optimal or complete debulking surgery for primary EOC (FIGO IIb-IV) between 2008 and 2015 from the Netherlands Cancer Registry. TTC was divided into three groups based on the interquartile range (IQR). Early (<25%) and prolonged (>75%) TTC were compared to intermediate TTC (25-75%). Logistic regression was used to identify factors associated with a prolonged TTC and multivariable Cox regression to evaluate the independent effect of treatment interval on overall survival (OS). Patients receiving primary debulking surgery (PDS) and patients receiving interval debulking surgery (IDS) were analyzed separately.

Results: 4097 patients were included, 1612 underwent PDS and 2485 IDS. Median TTC was 29 days (IQR 24-37). Age ≥ 65, complete debulking surgery, postoperative complications, and hospitalization ≥10 days were independently associated with a longer TTC for both PDS and IDS. TTC in the longest quartile was associated with poor OS after both PDS (Hazard Rate (HR) 1.43, 95% CI 1.09-1.88) and NACT-IDS (HR 1.22 (1.02-1.47)) when compared to the intermediate TTC, but only in patients with no macroscopic residual disease after surgery.

Conclusions: Our study provides evidence that delayed initiation of adjuvant chemotherapy is an independent prognostic factor for worse overall survival after complete (interval)debulking surgery. We advise to start adjuvant chemotherapy within five to six weeks after debulking surgery.