Prognostic Value of the Royal Marsden Hospital Score in Patients with De Novo Metastatic Colorectal Cancer Receiving First-Line Systemic Therapy.

Background: The Royal Marsden Hospital (RMH) score is a simple prognostic score based on serum albumin, lactate dehydrogenase, and the number of metastatic organ sites. Although its prognostic value has been demonstrated across several advanced cancer populations, evidence specifically in patients with de novo metastatic colorectal cancer (mCRC) initiating first-line treatment remains limited. Methods: This single-center retrospective cohort study included 189 patients with de novo mCRC who initiated first-line systemic treatment between January 2015 and January 2026. Patients were classified as low risk (RMH score 0-1) or high risk (RMH score 2-3). Progression-free survival (PFS) and overall survival (OS) were estimated using the Kaplan-Meier method, and factors independently associated with survival outcomes were evaluated using multivariable Cox regression. Results: Of the 189 patients, 142 (75.1%) were classified as low risk and 47 (24.9%) as high risk. Median PFS and OS for the entire cohort were 11.3 and 27.4 months, respectively. Median PFS was 11.8 months in the low-risk group and 7.6 months in the high-risk group (p < 0.001). Median OS was 33.8 and 13.7 months, respectively (p < 0.001). After adjustment for relevant clinicopathological factors, high-risk RMH status remained independently associated with shorter PFS (HR, 2.16; 95% CI, 1.51-3.09; p < 0.001) and OS (HR, 2.95; 95% CI, 2.03-4.29; p < 0.001). Conclusions: The RMH score was independently associated with both PFS and OS in patients with de novo mCRC initiating first-line systemic treatment. Based on simple and routinely available baseline parameters, the RMH score may serve as a complementary prognostic marker alongside established clinical and molecular factors.