Objective: Although the incidence of stomach cancer is decreasing in the world, its incidence is still high in Iran. Despite different treatments for cancer, disease recurrence, and death may occur in some patients. Various factors affect survival and recurrence after treatment. This study aims to identify factors affecting overall survival (OS) and disease-free survival (DFS) in patients with gastric cancer (GC) using a random survival forest (RSF).

Patients and Methods: In this retrospective study, 553 patients with GC, diagnosed between 2010 and 2018 in Kurdistan province in the west of Iran, were assessed. Important factors of OS and DFS were identified using the COX model and RSF. Analysis of data was implemented by R free software version 3.5.3.

Results: The mean (Standard Deviation(SD)) age of patients was 66.99 (13.3) years. The median of OS and DFS was 18 and 37.5 months, respectively. Using RSF, the important affected factors on OS were tumor grade, stage, age, recurrence, surgery, and metastasis, respectively. Also according to the RSF model, stage, tumor grade, radiotherapy, tumor site, surgery, and age were the important risk factors for DFS. Based on the prediction error criterion, the random survival forest performed well in predicting disease-free survival. meanwhile, both RSF and Cox models had the same performance in predicting overall survival.

Conclusions: Due to the relationship between tumor grade, disease stage and age, the random survival forest identified these variables as important variables in predicting both outcomes, although the Cox model was not able to detect these factors, which indicates better performance of RSF.