Question Does hyperthermic intraperitoneal chemotherapy (HIPEC) after primary or interval cytoreductive surgery increase survival in patients with ovarian cancer? Findings In this randomized clinical trial of 184 women with ovarian cancer, among those who underwent interval cytoreductive surgery after neoadjuvant chemotherapy, the addition of HIPEC decreased recurrence and increased overall survival; however, in patients undergoing primary cytoreductive surgery, progression-free survival and overall survival were not improved. No unresolved serious HIPEC-related adverse events were found in either group. Meaning These results suggest that HIPEC after interval cytoreductive surgery may increase progression-free and overall survival in patients with ovarian cancer who receive neoadjuvant chemotherapy. This randomized clinical trial of women with ovarian cancer compares the outcomes of hyperthermic intraperitoneal chemotherapy after primary vs interval cytoreductive surgery. Importance Ovarian cancer has the highest mortality rate among gynecologic malignant tumors. Data are lacking on the survival benefit of hyperthermic intraperitoneal chemotherapy (HIPEC) in women with ovarian cancer who underwent primary or interval cytoreductive surgery. Objective To assess the clinical benefit of HIPEC after primary or interval maximal cytoreductive surgery in women with stage III or IV primary advanced ovarian cancer. Design, Setting, and Participants In this single-blind randomized clinical trial performed at 2 institutions in South Korea from March 2, 2010, to January 22, 2016, a total of 184 patients with stage III or IV ovarian cancer with residual tumor size less than 1 cm were randomized (1:1) to a HIPEC (41.5 °C, 75 mg/m 2 of cisplatin, 90 minutes) or control group. The primary end point was progression-free survival. Overall survival and adverse events were key secondary end points. The date of the last follow-up was January 10, 2020, and the data were locked on February 17, 2020. Exposures Hyperthermic intraperitoneal chemotherapy after cytoreductive surgery. Main Outcomes and Measures Progression-free and overall survival. Results Of the 184 Korean women who underwent randomization, 92 were randomized to the HIPEC group (median age, 52.0 years; IQR, 46.0-59.5 years) and 92 to the control group (median age, 53.5 years; IQR, 47.5-61.0 years). After a median follow-up of 69.4 months (IQR, 54.4-86.3 months), median progression-free survival was 18.8 months (IQR, 13.0-43.2 months) in the control group and 19.8 months (IQR, 13.7-55.4 months) in the HIPEC group ( P = .43), and median overall survival was 61.3 months (IQR, 34.3 months to not reported) in the control group and 69.5 months (IQR, 45.6 months to not reported) in the HIPEC group ( P = .52). In the subgroup of interval cytoreductive surgery after neoadjuvant chemotherapy, the median progression-free survival was 15.4 months (IQR, 10.6-21.1 months) in the control group and 17.4 months (IQR, 13.8-31.5 months) in the HIPEC group (hazard ratio for disease progression or death, 0.60; 95% CI, 0.37-0.99; P = .04), and the median overall survival was 48.2 months (IQR, 33.8-61.3 months) in the control group and 61.8 months (IQR, 46.7 months to not reported) in the HIPEC group (hazard ratio, 0.53; 95% CI, 0.29-0.96; P = .04). In the subgroup of primary cytoreductive surgery, median progression-free survival was 29.7 (IQR, 17.2-90.1 months) in the control group and 23.9 months (IQR, 12.3-71.5 months) in the HIPEC group, and the median overall survival was not reached in the control group and 71.3 months (IQR, 45.6 months to not reported) in the HIPEC group. Conclusions and Relevance The addition of HIPEC to cytoreductive surgery did not improve progression-free and overall survival in patients with advanced epithelial ovarian cancer. Although the results are from a subgroup analysis, the addition of HIPEC to interval cytoreductive surgery provided an improvement of progression-free and overall survival. Trial Registration ClinicalTrials.gov Identifier: NCT01091636
