Clinical-pathological characteristics, follow-up, and survival of patients with early-onset vs late-onset colorectal cancer: Institutional experience in Argentina.

82 Background: The incidence of colorectal cancer (CRC) in young adults aged 50 or younger (Early Onset - EO) is increasing worldwide, while in patients over 50 years old (Late Onset - LO), it is declining. The objective is to compare the clinicopathological characteristics, time to diagnosis, and survival between Early Onset (EO) and Late Onset (LO) patients diagnosed with colorectal cancer (CRC). Methods: The sample was described using measures of central tendency and dispersion for continuous numerical variables and percentages for categorical variables. Clinical characteristics between Early Onset (EO) and Late Onset (LO) groups were compared using the Student’s t-test or Chi-square test. Kaplan-Meier curves and the Log-Rank Test were utilized to analyze mortality time. For multivariable analysis, a Cox regression model was applied. A p-value of less than 0.05 was considered statistically significant. The analysis was performed using RStudio. Results: A total of 460 patients were evaluated, with 343 diagnosed with colon adenocarcinoma and 117 with rectal cancer. Patients were grouped into two categories: the LO group with 408 (88.6%) patients and a mean age of 69.3 (8.60 SD) years, and the EO group with 52 (11.3%) patients and a mean age of 41.9 (6.23 SD) years. The EO group presented a higher percentage of patients with a PS of 0 compared to the LO group. In the EO group, there was a predominance of left-sided colon cancer (40.4% vs. 40.0%) and rectal cancer, especially in the middle and lower regions (30% vs. 18.8%), with disease diagnosed at stage III (26.9% vs. 26.5%) and IV (5.8% vs. 4.4%) compared to the LO group. Molecular testing for KRAS, NRAS, and BRAF mutations was more frequent in the EO group (19.2%, 3.8%, and 3.8%, respectively) compared to the LO group, as well as mismatch repair (MMR) status at 9.6% in the EO group vs. 6.9% in the LO group. The median time to diagnosis was 186 days in the LO group and 341 days in the EO group (p=0.21). Follow-up was 858 days in the LO group and 725 days in the EO group (p=0.18); while mortality was 200 (49.0%) in the LO group and 24 (46.2%) in the EO group, with a median survival of 1193 days for the LO group and 1414 days for the EO group, respectively (p=0.7). PS and stage were the most influential prognostic factors for mortality. Conclusions: In the comparison, the EO group showed a higher incidence of left-sided colon and rectal cancers, more advanced stages, better PS, and a greater number of molecular alterations, with a longer time to diagnosis and shorter follow-up. Although these differences were not statistically significant, they highlight the need to optimize prevention strategies and genetic counseling. Additional studies with a larger number of EO patients in real-life contexts are needed to generate more evidence that can improve clinical decision-making.