Development of Polygenic Risk Scores in Colon Cancer Patients Through the Study of Ancestry and Diversity in Genetic Maps of the Brazilian Population - ORIGEM Project

Colorectal cancer (CRC) is the third most common cancer diagnosed in both men and women. Approximately 70% of CRC cases originate from spontaneous point mutations in oncogenes, tumor suppressor genes, and genes related to DNA repair mechanisms (Nigin et al., 2023). The remaining 30% result from hereditary mutations, of which 5-6% involve high-penetrance genes. Genetic predisposition due to pathogenic germline variants in high-risk cancer-associated genes has been implicated in 2-8% of all CRC cases, increasing to 6-10% when considering pathogenic mutations in both high- and moderate-penetrance genes.

For individuals with certain hereditary cancer syndromes, the risk of developing colorectal cancer can reach 50-80% in the absence of endoscopic and/or surgical intervention. Therefore, characterizing high-, moderate-, and low-penetrance genes within a population is crucial for understanding hereditary tumorigenesis and guiding more cost-effective screening strategies.

Genetic studies comparing genomes from populations of different ethnic backgrounds have demonstrated that ancestry plays a significant role in genetic predisposition to CRC. Given the high level of genetic admixture in the Brazilian population, studies focused solely on populations of European ancestry fail to provide a representative model for application in highly admixed populations like Brazil.

In this context, the present study aims to utilize next-generation sequencing (NGS) in a cohort representative of the Brazilian population with CRC and controls to develop a Polygenic Risk Score (PRS). This score could impact cancer screening and prevention strategies, as well as genetic counseling for patients and their families. The hypothesis is that genetic mapping-including ancestry, germline, and tumor genetic variability-in Brazilian colorectal cancer patients will provide valuable data for developing a PRS that may eventually guide more targeted and cost-effective screening strategies for our population.