External validation of chemotherapy response score system for histopathological assessment of tumor regression after neoadjuvant chemotherapy in tubo-ovarian high-grade serous carcinoma

Objective: The chemotherapy response score (CRS) system based on histopathological examination has been recently proposed for tubo-ovarian high-grade serous carcinoma (HGSC) to assess response to neoadjuvant chemotherapy (NAC). This study was aimed at validating the CRS system in an external cohort of tubo-ovarian HGSC patients. Methods: This study included 110 tubo-ovarian HGSC patients who underwent NAC followed by interval debulking surgery. The 3-tiered CRS of the omental and adnexal tissue sections was determined by 3 independent pathologists. Differences in patient outcomes according to CRS were analyzed. Results: The CRS system was highly reproducible among the 3 pathologists. Fleiss' kappa value and Kendall's coefficient of concordance for the omental CRS were 0.656 and 0.669, respectively. The omental CRS significantly predicted progression-free survival (PFS). The median PFS of patients whose tumors exhibited the omental CRS 1–2 (15 months) was significantly shorter than that of patients with an omental CRS of 3 (19 months; p=0.016). In addition, after adjusting for age, stage, and debulking status, the omental CRS was an independent prognostic factor for PFS of tubo-ovarian HGSC patients who were treated with NAC (adjusted hazard ratio [HR]=1.74; 95% confidence interval [CI]=1.05–2.87). Conclusion: The CRS system for assessing NAC response was a reproducible prognostic tool in our cohort. The application of the CRS system after NAC can improve survival estimation in HGSC patients.