Background: The randomized, phase 3 OVHIPEC-1 trial (NCT00426257) investigated the addition of hyperthermic intraperitoneal chemotherapy (HIPEC) to interval cytoreductive surgery in patients with stage III epithelial ovarian cancer who were ineligible for primary cytoreduction. OVHIPEC-1 previously demonstrated improved recurrence-free and overall survival after 4.7 years of follow-up. Here, we report the final survival outcomes after ten years of follow-up. In addition, we report new data on the subsequent anti-cancer treatments given after disease progression. Methods: Patients were randomized to receive interval cytoreductive surgery with or without HIPEC, after receiving three cycles of neo-adjuvant carboplatin and paclitaxel. Randomization was performed at the time of surgery when either complete (no visible disease) or optimal cytoreduction (residual tumor measuring <10mm in diameter) was anticipated. All patients received an additional three cycles of adjuvant systemic chemotherapy. We analyzed survival according to the intention-to-treat principle using stratified log-rank tests and Kaplan-Meier methods. Subsequent lines of therapy were compared between arms. Results: At a median follow-up of 10.1 years, 114 of 123 patients (92.7%) who underwent surgery alone and 109 of 122 patients (89.3%) who had surgery-plus-HIPEC experienced recurrence, progression, or death from any cause. Median recurrence-free survival was 10.7 months in the surgery group compared to 14.3 months in the surgery-plus-HIPEC group (HR, 0.63; 95% confidence interval [CI], 0.48-0.83; stratified P<0.001). One hundred and eight patients (87.8%) in the surgery group have died as compared to 100 patients (82.0%) in the surgery-plus-HIPEC group. Median overall survival was 33.3 versus 44.9 months (HR, 0.70; 95% CI, 0.53-0.92; stratified P=0.011), respectively. Subsequent anti-cancer therapies, including chemotherapy (platinum and non-platinum based), secondary surgery, poly (ADP-ribose) polymerase (PARP) inhibitors and bevacizumab, were received by 104 patients (84.6%) in the surgery group and 100 patients (82.0%) in the surgery-plus-HIPEC group. The median number of subsequent systemic treatment lines was 2 (IQR 1-3) in both arms. Conclusions: This study provides the first long-term survival analysis of HIPEC in ovarian cancer and confirms the benefit of HIPEC in patients with primary stage III epithelial ovarian cancer undergoing interval cytoreductive surgery. No imbalance in subsequent therapy after disease recurrence was found that could explain the improved overall survival after HIPEC. Clinical trial information: NCT00426257.