The aim of the study was to investigate if time to start chemotherapy (TTC) after primary debulking surgery (PDS) impacted relative survival (RS) in advanced epithelial ovarian/fallopian tube/primary peritoneal cancer (EOC).

Nationwide population-based study of women with EOC FIGO stages IIIC-IV, registered 2008–2018 in the Swedish Quality Register for Gynecologic Cancer, treated with PDS and chemotherapy. TTC was categorized into; ≤21 days, 22-28 days, 29-35 days, 36-42 days and > 42 days. Relative survival (RS) was estimated using the Pohar-Perme estimate of net survival. Multivariable analyses of excess mortality rate ratios (EMRRs) were estimated by Poisson regression models.

In total, 1694 women were included. The median age was 65.0 years. Older age and no residual disease were more common in TTC >42 days than 0–21 days. The RS at 5-years was 37.9% and did not differ between TTC groups. In the R0 (no residual disease) cohort (n = 806), 2-year RS was higher in TTC ≤21 days (91.6%) and 22-28 days (91.4%) than TTC >42 days (79.1%). TTC >42 days (EMRR 2.33, p = 0.026), FIGO stage IV (EMRR 1.83, p = 0.007) and non-serous histology (EMRR 4.20, p < 0.001) were associated with 2-year worse excess mortality compared to TTC 0–21 days, in the R0 cohort. TTC was associated with 2-year survival in the R0 cohort in FIGO stage IV but not in stage IIIC. TTC was not associated with RS in patients with residual disease.

For the entire cohort, stage IV, non-serous morphology and residual disease, but not TTC, influenced 5-year relative survival. However, longer TTC was associated with a poorer 2-year survival for those without residual disease after PDS.