59 Background: Over the last decades the incidence of EOCRC (age 50 or less) has dramatically increased, and so has the scientific interest in this field, given that clinical and molecular characteristics in these patients are not well understood, and may be critical to identify prognostic factors. Methods: We conducted a retrospective analysis of 554 patients with metastatic colorectal cancer (mCRC), analyzing the PFS and OS of 68 (12.25%) patients with EOCRC, as well as their clinical and molecular characteristics. We used a log-rank test to compare PFS and OS, and the estimate of hazard ratio (HR) between the studied groups was calculated by means of Cox proportional hazard model. We also used the exact test of Fisher to identify significant association between categoric variants, while Mann-Whitney test was applied to identify significant differences between numeric values. Results: We performed a survival analysis: those patients with EOCRC had significantly higher median PFS in first line of treatment (16.2 vs. 11.3 months, p = 0.042) and significantly higher median OS (121.5 vs. 58.1 months, p = 0.011). Several characteristics were significantly more frequent in patients with EOCRC (n=68): BMI < 18.5 (n = 16, OR = 1.9, p = 0.046), primary tumor site at transverse colon (n = 9, OR = 2.61, p = 0.03) and ECOG 0 (n = 32, OR = 2.21, p = 0.003). Having peritoneal metastases almost reached statistical signification (n = 17, OR = 1.82, p = 0.055). Some other characteristics were less frequent: BMI 25-30 (n = 13, OR = 0.51, p = 0.046), primary tumor site at sigmoid colon (n = 14, OR = 0.49, p = 0.038) and former-smoker status (n = 7, OR = 0.44, p = 0.048). Moreover, mean values of LDH at diagnosis were significantly higher in EOCRC patients (359 U/L vs. 280 U/L, p = 0.015). EOCRC patients received a significantly higher number of lines of chemotherapy (2.94 vs. 2.38, p = 0.027) and underwent more surgeries (2,42 vs. 1.24, p < 0,001) than patients with > 50 years. Significant differences in tumor mutational status (BRAF, KRAS, NRAS, MSI, PI3K and HER2), sex, primary tumor resection or number of metastatic sites between groups were not found. Conclusions: This retrospective analysis showed that EOCRC patients had significant higher rates of PFS in first-line treatment and OS. Moreover, EOCRC patients had more frequently BMI < 18.5, primary tumor located at transverse colon and ECOG 0.
