1050 Prognostic Implications of Histological Tumor Regression (böhm’s Score) in Patients Receiving Neoadjuvant Chemotherapy for Advanced Epithelial Ovarian Carcinoma

Introduction/Background The primary objective of this study was to determine the prognostic significance of Bohm's histopathological regression score in patients who received neoadjuvant chemotherapy (NACT) for the treatment of advanced epithelial ovarian carcinoma. Methodology This was a retrospective cohort study of patients who received NACT followed by interval debulking surgery at the European Institute of Oncology (Milan, Italy), between 2007 and 2022 for which Bohm's score was evaluated. The three-point histopathological regression score of Böhm was used to classify chemotherapy response as follows: chemotherapy response score (CRS) CRS 1, no or minimal; CRS 2, partial; CRS 3, complete or near complete. Progression-free survival (PFS) and overall survival (OS) were compared between the three subgroups using the log-rank test and Cox proportional hazards models to control for confounders. Results In total, 382 patients meeting inclusion criteria were included. CRS 1, 2, and 3 were observed in 120 (31.4%), 195 (51.1%), and 67 (17.5%) women, respectively. The 3-year PFS for patients with CRS 1, 2, and 3 was 8.0% [95% CI, 3.3%-15.5%], 10.4% [95% CI, 5.2%-17.7 %] and 30.3% [95% CI, 18.5%-43.0%], respectively (p= 0.0001). After controlling for age, stage, and residual tumor, CRS 3 was associated with better PFS than CRS 1–2 (HR= 0.51; 95%CI 0.34–0.76). The 3-year OS for patients with CRS 1, 2, and 3 was 51.7% [95% CI, 38.0%-63.6%], 50.5% [95% CI, 40.4%-59.8%] and 64.5%[95% CI, 51.2%-76.5%], respectively, but the difference was not statistically significant (p= 0.12). Conclusion This difference held significance on multivariate assessment whilst controlling for clinically meaningful variables, such as age, stage and residual disease status. Disclosures The authors have no conflicts of interest to declare.