Objectives To evaluate the prognostic significance of residual tumor size on computed tomography (CT) after upfront surgery for advanced ovarian cancer (AOC).

Methods We collected data of patients with stage III-IV high-grade serous carcinoma of the ovary (HGSC) who underwent optimal cytoreduction between 2013 and 2018. They took CT between upfront surgery and adjuvant chemotherapy. We evaluated surgical and radiological residual tumor size after upfront surgery, which was divided into R0 (no residual lesion) and R1 (residual tumor <1 cm).

Results A total of 106 patients received surgical R0 (n=73, 68.9%) and R1 (n=33, 31.1%). Among all patients, 66 (62.3%) and 40 (37.7%) showed radiologic R0 and R1, respectively. In 73 patients with surgical R0, 56 (76.7%) and 17 (23.3%) showed radiologic R0 and R1, whereas 10 (30.3%) and 23 (69.7%) were observed in 33 with surgical R1, respectively. In terms of survival, both surgical R0 and radiological R0 showed better progression-free survival (PFS; 26 vs. 16 mons; 33 vs. 15 mons; p <0.05), whereas no difference in overall survival based on residual tumor size. In multivariate analysis, surgical R0 was the only factor that improved PFS (adjusted HR, 0.45; 95% CI, 0.21–0.98). On the other hand, radiologic R0 didn’t reach statistical significance (adjusted HR, 0.58; 95% CI, 0.14–1.03).

Conclusions Although patients with radiologic R0 showed better PFS in univariate analysis, there was no significance in multivariate analysis. Therefore, surgical R0 was more important factor to predict the prognosis of disease than radiologic R0 in AOC patients with optimal cytoreduction.