Feasibility and Prognostic Value of an Ovarian NAR-like Score in Advanced Ovarian Cancer Treated with Neoadjuvant Chemotherapy and Interval Debulking Surgery

Background: Neoadjuvant chemotherapy followed by interval debulking surgery is an established treatment strategy for selected patients with advanced epithelial ovarian cancer. However, simple postoperative prognostic tools integrating pre-treatment disease extent and post-treatment pathological stage remain limited. The neoadjuvant rectal (NAR) score was originally developed as a composite stage-migration endpoint in rectal cancer and has subsequently been explored in other solid tumors. We evaluated the feasibility and prognostic value of an ovarian NAR-like score (oNAR) in patients with advanced ovarian cancer treated with neoadjuvant chemotherapy and interval debulking surgery. Methods: This single-center retrospective cohort included patients with advanced ovarian cancer treated with platinum-taxane-based neoadjuvant chemotherapy followed by interval debulking surgery. The oNAR score was calculated using clinical T category before neoadjuvant chemotherapy and pathological T and N categories after interval surgery: oNAR = [5 × ypN − 3 × (cT − ypT) + 12]2/9.61. The primary analysis evaluated oNAR as a continuous score. Low, intermediate, and high oNAR categories based on the original rectal NAR thresholds were used only for exploratory visualization. The primary endpoint was progression-free survival (PFS). Cox regression, Kaplan–Meier analysis, log-rank testing, Harrell concordance index, and exploratory ROC analysis were used. Results: Among 74 reviewed records, 73 patients had sufficient cT, ypT, and ypN data for oNAR calculation and were included in the primary analysis. Thirty-one PFS events and 10 deaths occurred. The median oNAR was 14.98 (IQR, 14.98–30.07). As a continuous variable, higher oNAR was associated with shorter PFS (HR per 1-point increase, 1.036; 95% CI, 1.010–1.061; p = 0.0055), corresponding to an HR of 1.42 per 10-point increase. The Harrell C-index for PFS was 0.669. In a parsimonious comparison, oNAR showed higher discrimination than ypN alone and discrimination comparable to a combined ypT/ypN model. PFS differed significantly across low-, intermediate-, and high-oNAR groups (log-rank p = 0.0053). Median PFS was not reached in the low-oNAR group, compared with 13.47 months in the intermediate group and 12.09 months in the high group. The association persisted in sensitivity analyses restricted to patients with complete/optimal cytoreduction, maximal cytoreduction, and high-grade serous histology. Conclusions: The oNAR score was feasible to calculate using routinely available clinical and pathological staging variables and was significantly associated with PFS after neoadjuvant chemotherapy and interval debulking surgery. These findings support oNAR as a feasible stage-migration-based prognostic summary that may help capture post-NACT pathological T/N information and warrants external validation in larger ovarian cancer cohorts.