Spectrum of germline pathogenic variants among patients with cancer in Mexico.
Authors: Rodriguez Olivares Jose Luis , Bourlon De Los Rios Maria Teresa , De la Mora Molina Hector , Arteaga Vazquez Jazmin , Morales Alfaro Andrea , Carrillo Bedoya Araceli , Quintero Beulo Gregorio , Roberto Iván Sánchez Reyes , Castillo Danielle , Herzog Josef , Weitzel Jeffrey N. , Chavarri Guerra Yanin 
Published: June 2023

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Background: Up to 10% of patients with cancer harbor pathogenic germline variants (PVs) in one or more cancer susceptibility genes. Genetic cancer risk assessment (GCRA) is an important tool for the management of patients with cancer. It allows the identification of candidates for structured screening protocols, risk reduction strategies, targeted therapies and cascade testing. Knowledge about the prevalence and spectrum of PVs is limited among underrepresented populations. We studied the prevalence of germline PVs in a cohort of Mexican patients with cancer. Methods: Between April 2017 and September 2022, patients with diagnosis of cancer who met clinical criteria for GCRA according to international guidelines (NCCN) and were enrolled in the international Clinical Cancer Genomics Community Research Network (CCGCRN) registry at Instituto Nacional de Ciencias Medicas y Nutricion Salvador Zubiran were included. Cancer risk counseling and germline multi-gene panel testing were performed. Post-test counseling and cascade testing with known PV analysis was offered. Results: 1322 patients met inclusion criteria (probands n = 1027, relatives n = 295). Among the probands, 72.4% (744/1027) were women, median age at cancer diagnosis was 48.2 years (range 1-88) and 9.8% (n = 101) had more than one primary tumor. 14.5% (149/1027) of probands had a positive result in which 152 PV were identified ( BRCA1 n = 39, BRCA2 n = 33, ATM n = 11, CHEK2 n = 11, MLH1 n = 11, TP53 n = 7, PALB2 n = 7, NF1 n = 6, MSH2 n = 5, MSH6 n = 3, PTEN n = 3, APC n = 2, BRIP1 n = 2, CDH1 n = 2, RB1 n = 2 and 1 PV in the genes: CDKN2A, MAX, MUTYH, NBN, PTCH1, RAD50, SDHA and SDHB). The frequency of PV according to cancer diagnosis was: breast 15.5% (82/527), prostate 2% (4/198), ovarian 15.6% (12/77), colorectal 26.6% (16/60) and pancreatic 11.9% (5/42). The frequency of recurrent, potentially founder PVs in their respective genes was as follows: BRCA1 del(exons9-12) 30.7% (12/39) and CHEK2 c.707T > C 81.8% (9/11). Among the relatives referred for cascade testing the frequency of PV was 40% (118/295), 18.6% (55/295) had personal history of cancer with a median age at diagnosis of 47 years. Conclusions: Our results show a wide spectrum and a variable frequency of PVs among one of the largest examined cohorts of Mexican patients with cancer, with a high frequency of PVs among cases of breast, ovarian, and colorectal cancer. In contrast to reports from other populations, there was very low frequency of PVs among patients with prostate cancer. The outcomes of this study add to our understanding of the genetic epidemiology of cancer in the Mexican population, and support creating GCRA programs to improve access to multi-gene panel testing among underrepresented patients in limited resource settings.