Abstract 5273: Changes in the tumor immune microenvironment during disease progression in gynecological carcinosarcoma: Exploratory analysis from the randomized ROCSAN GINECO trial

Abstract Background: Gynecologic carcinosarcomas (CS) are highly aggressive/rare tumors. Most patients relapse after first-line therapies and responses to systemic therapy remain low. ROCSAN (NCT03651206) is a multicentric randomized phase II evaluating dostarlimab (anti-PD1) in combination with niraparib (PARPi) compared to standard of care in the treatment of metastatic/recurrent (R/M) CS. Objective: Mandatory tumor tissue archival from naïve initial disease (ND) & baseline biopsies at relapse (R/M) were used to decipher the biological changes of CS in R/M disease vs. ND. Methodology: bulk transcriptomic profiling was performed on paired samples from 60/63 included patients. Differential expression, gene ontology (GO), and immune cell deconvolution were performed. Our previously reported HOT signature was computed (GSVA) (PMID36038492). Additionally, a 7-color multiplex immunofluorescence (mIF) analysis of 52 paired samples (CD20, Ki67, CD3, CD8, FoxP3, panCK, DAPI) was done to evaluate total T cells, CD8 and CD4 Teff, Treg, and B cells cell densities and tertiary lymphoid structures (TLS). Results: Differential expression analysis adjusted for FIGO stage, primary site and number of previous systemic therapies identified 1, 502 and 584 genes up and down regulated respectively in R/M disease vs. ND. Among 13 immune checkpoints (ICP) and 22 of their ligands (ICPL), 8 ICP (TIGIT, HAVCR2, CTLA4, VSIR, CD40LG, TNFRSF9, CD27, ICOS) and 4 ICPL (PD-L1, PDCD1LG2, CD80, CD86), were upregulated in R/M disease vs. ND. Top GO enriched pathways in R/M vs. ND included immune activating pathways, regulation of lymphocyte activation and positive regulation of cytokine production. Among 50 biological hallmarks (GSEA), R/M showed a significant enrichment in inflammatory response, TNFA signaling via NFKB, and IFNG response vs. ND. Deconvolution analysis found an increase in NK cells (P=0.024), Macrophage/Monocyte (P=0.001) and Neutrophils (P=0.023) in R/M disease vs. ND. The HOT signature score was found to be increased in R/M disease vs. ND (P=0.01). The proportion of HOT CS (score>0) was 33/60 (55%) and 23/60 (38%) in R/M and ND respectively. Among the 37/60 (62%) COLD CS (score<0) in ND, 18/37 (49%) became HOT in R/M. Among the 23/60 (38%) HOT CS at ND, 8/23 (35%) became COLD at R/M. mIF analysis showed that total T cells (P=0.037), CD8 Teff (P=0.039), CD4 Teff (P=0.034), and CD4 Treg (P=0.003) increased in R/M disease vs. ND. Intriguingly, TLS density decreased in R/M disease vs. ND (P=0.035). Conclusion: When compared with ND, R/M CS host a greatest immunologically active microenvironment, as suggested by the changes observed in the HOT score and HOT/COLD phenotype, implying potentially more activity for immune therapy in relapse than for localized initial therapy. Whether this could be used to select patients for immunotherapy should be investigated. Citation Format: Sonia Canjura-Rodriguez, Cassandra Assaf, Victor Heurtier, Annalisa Pesavento, Justine Berthet, Audrey Bellesoeur, Coriolan Lebreton, Sheik Emambux, Dominique Berton, Magali Provansal, Guillaume Bataillon, Lucas Michon, Jessie Auclair, Alexandra Lainé, Valéry Attignon, Christophe Caux, Anthony Ferrari, Ivan Bièche, Bertrand Dubois, Isabelle Ray-Coquard, Pierre Saintigny. Changes in the tumor immune microenvironment during disease progression in gynecological carcinosarcoma: Exploratory analysis from the randomized ROCSAN GINECO trial [abstract]. In: Proceedings of the American Association for Cancer Research Annual Meeting 2025; Part 1 (Regular Abstracts); 2025 Apr 25-30; Chicago, IL. Philadelphia (PA): AACR; Cancer Res 2025;85(8_Suppl_1):Abstract nr 5273.