RT Journal Article SR Electronic T1 1050 Prognostic implications of histological tumor regression (Böhm’S score) in patients receiving neoadjuvant chemotherapy for advanced epithelial ovarian carcinoma JF International Journal of Gynecologic Cancer JO Int J Gynecol Cancer FD BMJ Publishing Group Ltd SP A394 OP A394 DO 10.1136/ijgc-2024-ESGO.770 VO 34 IS Suppl 1 A1 Zambetti, Benedetta A1 Vitis, Luigi Antonio De A1 Schivardi, Gabriella A1 Caruso, Giuseppe A1 Rosanu, Marina A1 Bruni, Simone A1 Betella, Ilaria A1 Achilarre, Maria Teresa A1 Garbi, Annalisa A1 Aloisi, Alessia A1 Biffi, Roberto A1 Maggioni, Angelo A1 Zanagnolo, Vanna A1 Carinelli, Silvestro A1 Ghioni, Mariacristina A1 Aletti, Giovanni A1 Colombo, Nicoletta A1 Multinu, Franceco YR 2024 UL http://ijgc.bmj.com/content/34/Suppl_1/A394.1.abstract AB 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.Abstract 1050 Figure 1