Survival analysis and associated factors in metastatic early-onset colorectal cancer vs. metastatic average-onset colorectal cancer.

e15549 Background: Early-onset colorectal cancer (EO-CRC) is defined as colorectal cancer diagnosed before age 50 and its incidence has been increasing during the last decade. Average-onset colorectal cancer (AO-CRC) has presented a steady decline in incidence and related mortality over the past 20 years. There is controversy surrounding the disparities in outcomes and overall survival (OS) in EO-CRC vs. AO-CRC. Our study compared the OS and cause-specific survival (CSS) between metastatic EO-CRC (mEO-CRC) and metastatic AO-CRC (mAO-CRC) and identified associated factors. Methods: Data on patient characteristics, tumor characteristics, incidence and mortality were obtained from the SEER database from 2010 to 2020. We identified 23,278 individuals aged > 18 with confirmed diagnosis of all histologic subtypes of metastatic CRC (M1 on TNM stage) using ICD-O-3 site code C180, C182-9, C209 and histology codes: 8000, 8010, 8012, 8013, 8020-2, 8031-33, 8041, 8045, 8070-2, 8083, 8123-4, 8140, 8144-45, 8201, 8210-11, 8213, 8220-1, 8240, 8243-46, 8249, 8253, 8255, 8260-3, 8261-3, 8265, 8310, 8323, 8480-1, 8490, 8507, 8510, 8550, 8560, 8570, 8574, 8936, 8980. OS distributions and CCS were conducted using the Kaplan-Meier method and log-rank test was used to assess differences between mEO-CRC and mAO-CRC. Cox regression model used to assess associations between variables. Results: mEO-CRC constituted 17.79% of the cases, while 82.21% were mAO-CRC. Most patients with mEO-CRC were between 45-49 years old (47.66%), males (52.16%), white (72.57%), with histology of adenocarcinoma (87.30%). Left colon tumors were most prevalent in both groups (40.26%), but higher among mEO-CRC than in mAO-CRC (49.63% vs 38.23%, p < 0.001). mEO-CRC were more likely to receive chemotherapy (87.23% vs. 66.66%, p < 0.001) and radiotherapy (14.92% vs. 9.51%, p < 0.001), while surgery was similar in both groups (87.71% vs. 88.52%, p = 0.140). Patients with mEO-CRC had a higher OS (HR: 1.53, CI 95% 1.47-1.59, p < 0.001), as well as a higher CSS (HR: 1.33, 95% CI: 1.27-1.39, p < 0.001) when compared to mAO-CRC. mEO-CRC also had a significantly better median overall survival (30 months vs. 18 months p < 0.001). Factors associated with worse OS include mAO-CRC (p < 0.001), mucinous adenocarcinoma (p < 0.001), male sex (p 0.003) and no surgical intervention (p < 0.001). Conclusions: Patients with mEO-CRC had better OS and CSS when compared to patients with mAO-CRC and were more likely to receive cancer-directed therapy which could be explained by the mEO-CRC cohort having a higher performance status, less comorbidities, and better tolerance to cancer-related therapy. Factors associated with worse OS and CSS are mAO-CRC, mucinous adenocarcinoma, male sex and lack of surgical intervention. Furthermore, it is crucial to continue studying potential candidates who would benefit from early CRC screening.