Chemotherapy Response Score (CRS): A comprehensive review of its prognostic and predictive value in High-Grade Serous Carcinoma (HGSC)

Ovarian carcinoma, the second most common gynecological cancer in Western countries, is frequently diagnosed at advanced stages, necessitating complex treatment strategies. While cytoreductive surgery remains the standard for improving survival, neoadjuvant chemotherapy (NACT) has become essential for cases unsuitable for immediate surgery, aiming to reduce tumor burden preoperatively. Introduced in 2015, the Chemotherapy Response Score (CRS) is now a key histopathological tool for assessing response to NACT, stratifying patients into three response categories. CRS3 is associated with improved progression-free survival (PFS) and overall survival (OS), while CRS1 and CRS2 are linked to poorer outcomes. Validated across clinical cohorts, CRS has proven valuable not only as a prognostic tool but also as a predictor for molecular-targeted therapies, such as PARP inhibitors, especially in BRCA wild-type patients. Studies also suggest a potential role for CRS in guiding the use of PD-L1 inhibitors, especially in partial responders (CRS1 and CRS2), where immunotherapy may complement chemotherapy. In the present paper we exlored the actual knowledge on CRS scoring for ovarian carcinoma. Diagnostic and prognostic implications of CRS as well as its correlation with therapeutic response and other biomarkers are discussed.