Alejandro González-Motta, Unidad Funcional de Radioterapia, Centro de Tratamiento e Investigación sobre Cáncer, Luis Carlos Sarmiento Angulo; Centro Javeriano de Oncología, Hospital Universitario San Ignacio; Bogotá, Colombia
Gabriela Negrete-Tobar, Departamento de Radioterapia, Centro Javeriano de Oncología Hospital Universitario San Ignacio; Pontificia Universidad Javeriana, Facultad de Medicina; Bogotá, Colombia
Oscar A. Messa-Botero, Departamento de Patología, Clínica Colsanitas/Centro de Tratamiento e Investigación sobre Cáncer, Luis Carlos Sarmiento Angulo; Departamento de Patología, Hospital Universitario San Ignacio; Bogotá, Colombia
Juliana Pineda-Ortega, Pontificia Universidad Javeriana, Facultad de Medicina, Bogotá, Colombia
Isabella Garciandía, Pontificia Universidad Javeriana, Facultad de Medicina, Bogotá, Colombia
Juan S. Álvarez-Martínez, Pontificia Universidad Javeriana, Facultad de Medicina, Bogotá, Colombia
Natalia Londoño-De Vivero, Pontificia Universidad Javeriana, Facultad de Medicina, Bogotá, Colombia
Ricardo Bruges-Maya, Pontificia Universidad Javeriana, Facultad de Medicina; Departamento de Oncología Médica, Hospital Universitario San Ignacio. Bogotá, Colombia Bogotá, Colombia
Background: In Colombia, gastric cancer is fifth in incidence (12.8 cases per 100,000) and third in mortality (9.9 cases per 100,000). Microsatellite instability (MSI), a phenotype in gastric cancer treatment, lacks comprehensive exploration in Colombian and Hispanic/Latino populations. Data scarcity hinders immunotherapy approval in middle-income countries. Objective: Characterize the prevalence of MSI phenotype in Colombian patients with gastric and gastroesophageal junction cancer. Material and methods: We measured MLH-1, MSH-2, MSH-6, and PMS-2 expression in tumor pathology by immunohistochemistry markers. We conducted descriptive analysis and Fisher’s test to identify associations for MSI expression. Results: Final sample size was 106 patients, mean age of 62.5 years (25-93 ± 14.2). Prevalence of MSI was 12.26% (n = 13). We found an association between older age and positive MSI (p = 0.0042), as well as with non-diffuse histologic subtypes (p = 0.019). Conclusions: Prior studies report 22% MSI phenotype prevalence in gastric tumors, mostly in developed countries, excluding Hispanic/Latino populations. Identifying the prevalence of MSI in our population as 12.26% could pave the way for approving immune blockade drugs as a treatment option for these patients in Latin American countries. Our data could be utilized to conduct cost-utility studies in support of this.
Keywords: Gastric cancer. Hypermutation Microsatellite instability. Mismatch repair. Gene silencing.