Abstract 3943: Determination of the molecular profile of Chilean patients with sporadic colorectal cancer

Introduction: Colorectal cancer (CRC) represents a major health problem worldwide, ranking third among the most frequent cancers and fourth in cancer mortality. In Chile CRC is the third leading cause of cancer death. CRC is a heterogeneous disease, and three carcinogenic pathways have been described to determine the molecular profile: The microsatellite instability (MSI), chromosomal instability (CIN) and methylator phenotype (CIMP). Several studies have tried to propose CRC molecular subgroups based on the 3ways described above since CIN, MSI and CIMP are not mutually exclusive and overlapping of the 3 ways is still unclear. The most recent subtyping of CRC was in 2015, where four molecular subtypes consensus (CMS 1 to 4) were established according to clinicopathological features, molecular pathways involved and mutational status of KRAS, BRAF and PI3KCA genes in order to encourage clinical translation. 21% of tumors failed to be categorized into these subtypes. This classification allows us to understand and determine the clinical, pathological and biological characteristics of CCR to provide customized therapies to patients. Aim: To describe the molecular profile of carcinogenic pathways CIN, MSI CIMP in Chilean patients with sporadic CRC. Material and Methods: Prospective analytical study of 56 patients operated between 2010-2016 at Clinica Las Condes, without neo-adjuvant treatment. DNA was extracted from normal and tumor tissue of each patient and using PCR amplification of several markers CIN, MSI and CIMP were defined. By combining the 3 variables analyzed, tumors were classified in Group-A (MSI-high), Group-B (MSI-low / CIMP-high / CIN-high), Group-C (MSI-low / CIMP-high / CIN-low), Group-D (MSI-low / CIMP-low / CIN-high) and Group-E (MSI- neg / CIMP-neg / CIN-neg). Results: In this study, tumors in Group-A (17%) are located on the right side in patients older than 60 years and early stages. Tumors Group-B / C (18,9%) occur in patients older than 60 years and BMI>25 kg / m2, with wall invasion pT3-T4 and late stages. Tumors of Group-D / E (54,7%) are the most frequent, located on the left side, without vascular invasion and moderately differentiated. Conclusions: This study allowed to classify Chilean patients in 3 subgroups considering the 3 main routes described for carcinogenesis development: CIN, MSI and CIMP, which are consistent with the percentages described by the global consortium. Studies that analyze MSI and CIMP or MSI and CIN have co