Introduction/Background Clinical benefit to immunotherapy (ICPI) has been limited to date in high-grade serous ovarian carcinoma (HGSOC), underpinning the necessity of better patient’s selection. Conversely, peripheral blood parameters such as neutrophil-to-lymphocyte ratio (NLR), platelet-to-lymphocyte ratio (PLR) and lymphocyte-to-monocyte ratio (LMR) have been correlated to ICPI benefit in various malignancies. As such, the present ancillary study from the NEOPEMBROV/GINECO phase II trial (NCT03275506) assessed these parameters as predictive biomarkers of pembrolizumab (P) adjunction to standard chemotherapy (CT) and interval debulking surgery for advanced HGSOC.

Methodology 91 patients were enrolled in the trial (P+CT arm: 61; CT arm: 30). Optimal cut-off values for baseline NLR, PLR, and LMR regarding progression-free survival (PFS) in the P+CT arm were determined by ROC curves. Subsequently, a composite blood score (CBS) integrating these three biomarkers was evaluated.

Results Using ROC-based optimal cutoff values, we observed in P+CT arm a positive predictive impact of NLR ≤4 vs >4 (median PFS: 26.2 vs 17.0 months; hazard ratio (HR) 0.48 ; 95% confidence-interval (95CI) 0.25–0.89; p<0.05), PLR ≤250 vs >250 (median PFS: 26.0 vs 17.2 months; HR 0.49 ; 95CI 0.26–0.91; p<0.05) and LMR ≥2 vs <2 (median PFS: 25.8 versus 17.0 months; HR 0.47 ; 95CI 0.23–0.93; p<0.05). CBS, defined as the combination of NLR ≤4 + PLR ≤250 + LMR ≥2 in a given patient led to the following median PFS: 30.7 vs 15.1 months (HR 0.31; 0.16–0.60; CBS positive (n=33) and negative (n=28), respectively; p<0.0001). Interestingly, none of these biomarkers were associated with enhanced PFS in the CT arm.

Conclusion Our study reports that baseline NLR, PLR, LMR and CBS are promising predictive biomarkers of P+CT treatment efficacy in newly diagnosed HGSOC. These exploratory results will require to be further assessed and validated in larger cohorts of patients with HGSOC and treated with ICPI.

Disclosures Stanislas Quesada: no COI

Isabelle Ray-Coquard: GINECO President

Camille Schiffler: no COI

Aude-Marie Savoye: no COI

Marie-Ange Mouret-Reynier

Florence Joly: honoraria or consultations fees for AstraZeneca, GSK, Janssen, Ipsen, Clovis, Amgen, Astellas, MSD, BMS, Bayer

Olfa Derbel Miled: no COI

Elsa Kalbacher: honoraria or consultations fees for Astrazeneca, GSK, Sanofi, Roche, Seagen

Alejandra Martinez: honoraria or consultations fees for GSK

Marianne Leheurteur: travel grants from MSD

Jérôme Meunier: no COI

Mathilde Martinez: no COI

Nicolas Cloarec: no COI

Laurence Venat-Bouvet: no COI

Dominique Berton: no COI

Frédéric Selle: honoraria or consultations fees for GSK, AstraZeneca, MSD, Eisai

Pierre-Alexandre Just: honoraria or consultations fees for GSK and Roche

Guillaume Bataillon: Consulting/Advisory Board for GSK

Isabelle Treilleux: no COI

Olivia Le Saux: honoraria or consultations fees for GSK, Clovis, MSD