Maintenance Therapy in Metastatic Gastric Cancer: A Multicenter Retrospective Study in Colombia

Background: Gastric cancer is the fifth most frequent cancer and the third cause of cancer-related death worldwide, with high incidence in Asia and Latin America. In Colombia, most cases are diagnosed at advanced stages. Platinum and fluoropyrimidine combinations remain the standard first-line treatment for metastatic disease, but the optimal duration of first-line chemotherapy and the role of maintenance strategies are not clearly established. The randomized phase II AIO MATEO trial showed that S-1 maintenance after induction chemotherapy achieved overall survival comparable to continued chemotherapy with less toxicity. Immunotherapy and targeted therapies (such as trastuzumab in HER2-positive disease) are also used in the maintenance setting in selected molecular subgroups. No Colombian data exist on the outcomes of these maintenance strategies.

Design: Observational, retrospective, multicenter cohort study based on review of medical records at four high-complexity cancer centers in Bogotá, Colombia: Hospital Universitario Fundación Santa Fe de Bogotá (coordinating center, through the Instituto de Cáncer Carlos Ardila Lülle), Centro de Tratamiento e Investigación sobre Cáncer Luis Carlos Sarmiento Angulo (CTIC), Clínica del Country and Los Cobos Medical Center.

Population: Adults (older than 18 years) with metastatic gastric cancer diagnosed and treated between 2013 and 2023 who achieved at least stable disease by RECIST after induction chemotherapy, with ECOG performance status of 2 or less, and who subsequently received maintenance therapy. All eligible patients will be included (census sampling); no sample size calculation is required.

Data collection: Data will be abstracted from institutional medical records into a single REDCap database hosted by Fundación Santa Fe de Bogotá. Each center will have restricted user accounts limited to its own patients. Records will be coded with an alphanumeric identifier, and the identification key will remain locally at each center and will not be uploaded. Variables include demographic and clinical characteristics, comorbidities, Helicobacter pylori status, histology (WHO and Lauren classifications, differentiation), molecular markers (microsatellite instability, PD-L1, HER2), AJCC 8th edition staging, induction and maintenance regimens and number of cycles, immunotherapy and targeted therapy, adverse drug reactions, laboratory values and tumor markers, dates of progression and relapse, vital status and cause of death.

Statistical analysis: Qualitative variables will be summarized with absolute and relative frequencies and quantitative variables with means and standard deviations or medians and interquartile ranges according to their distribution. Overall and progression-free survival will be estimated with the Kaplan-Meier method and reported as medians and survival rates. Exploratory comparisons of outcomes among maintenance types (fluoropyrimidines, immunotherapy, targeted therapy) will use bivariate tests and adjusted multivariable models, considering the molecular profile as a potential effect modifier. Analyses will be performed with IBM SPSS Statistics 25.

Ethics: The study is classified as research without risk under Colombian Resolution 8430 of 1993, and individual informed consent is not required for this retrospective record review. The protocol was approved by the Comité Corporativo de Ética en Investigación of Fundación Santa Fe de Bogotá (CCEI-18065-2025) and by the ethics committees of the participating institutions. Data will be handled in accordance with the Declaration of Helsinki and Colombian Law 1581 of 2012 on personal data protection, stored securely for five years and then destroyed.