Tumour–Stroma Ratio Is Associated With Platinum Resistance in Epithelial Ovarian Cancer: A Retrospective Cohort Study

Background: Platinum resistance remains a major therapeutic challenge in epithelial ovarian cancer (EOC). The tumour–stroma ratio (TSR) has emerged as a potential prognostic biomarker in several malignancies; however, its predictive value for platinum resistance in EOC remains unclear. Methods: This retrospective cohort study included 83 patients with EOC who underwent primary debulking surgery (PDS) or neoadjuvant chemotherapy followed by interval debulking surgery (NACT + IDS) between January 2017 and January 2024. TSR was assessed on haematoxylin and eosin–stained sections and classified as low (< 50%) or high (≥ 50%). The primary endpoint was platinum resistance. Secondary endpoints included overall survival (OS) and disease-free survival (DFS). Survival outcomes were analysed using the Kaplan–Meier method. Results: Platinum resistance was observed in 26.5% of patients. In the PDS cohort, TSR was not significantly associated with clinicopathological characteristics, platinum resistance, OS, or DFS. In contrast, in the NACT + IDS cohort, high TSR was significantly associated with platinum resistance (75% vs. 25%, p = 0.032). No significant differences in OS or DFS were detected according to TSR status in either treatment group, although patients with high TSR in the NACT + IDS cohort tended to show poorer survival outcomes. Conclusions: High TSR is associated with platinum resistance in patients with EOC treated with neoadjuvant chemotherapy. TSR may represent a simple and accessible predictive biomarker for identifying patients at increased risk of treatment resistance. Further validation in larger, prospective, multicentre studies is warranted.