Background: Gastric cancer ranks sixth in incidence and seventh in mortality worldwide. Intestinal-type gastric cancer is the most common histological subtype and is strongly associated with lifestyle factors including consumption of ultra-processed foods, high intake of red meat and high-salt foods, low consumption of fruits and vegetables, alcohol intake and tobacco consumption, as well as infection with Helicobacter pylori. Five-year survival ranges from 8% to 65.1% globally, and in Brazil it is approximately 34%, regardless of clinical stage. Conditional survival refers to the probability that a patient will survive an additional period, given that they have already survived a specified interval since diagnosis or initiation of treatment.
Objectives: To estimate 1- and 3-year conditional survival for patients with intestinal-type gastric cancer according to clinical stage, sex, and age group.
Methods: Patients aged 18 years or older, of both sexes, diagnosed with intestinal-type gastric cancer between 2000 and 2022 and registered in the São Paulo State Hospital-Based Cancer Registry were included. Sociodemographic and clinical variables were included in the survival analysis. Overall survival time was calculated from the date of diagnosis to the date of death (from cancer or any other cause) or the date of last follow-up. Survival probabilities were estimated using the Kaplan–Meier method, and conditional survival (the probability of surviving X additional years given survival for Y years after diagnosis) was calculated using life tables. Hazard ratios (HRs) and 95% confidence intervals (95%CI) were estimated using Cox proportional hazards regression. A significant level of 5% was adopted. Analyses were performed using SPSS for Windows v.25 and RStudio. This study is part of the ConeCta-SP project, which focuses on cancer knowledge and control in the State of São Paulo, Brazil and supported by the São Paulo Research Foundation (FAPESP) and the Health Secretariat of the State of São Paulo (Brazil).
Results: A total of 8,452 patients with intestinal-type gastric cancer were analyzed. Most were men (70.8%), with a mean age of 65.5 years (range 18 to 103 years). Most patients were diagnosed at advanced clinical stages: 26.7% and 36.5% were in stages III and IV, respectively. One-year, 3-year, and 5-year survival probabilities were 61.6%, 36.5%, and 29%, respectively. Patients with clinical stage IV disease had more than a sixfold higher risk of death compared with those in stage I (HR 6.82; 95%CI 6.25–7.44). In the conditional survival analysis for one additional year, patients diagnosed at early clinical stages maintained high and stable survival probabilities after the first year following diagnosis. In contrast, patients with stages III and IV showed improvements in conditional survival beginning after the second-year post-diagnosis. Women demonstrated better conditional survival than men in both 1-year and 3-years (HR 0.81; 95%CI 0.77-0.86).  
Conclusions: Prompt detection of gastric cancer allows earlier initiation of treatment and is associated with improved prognosis. Nevertheless, most cases continue to be diagnosed at advanced stages, leading to poor survival outcomes. Public health strategies focused on prevention, health promotion, and improvement of lifestyle-related risk factors are essential to reduce the burden of gastric cancer.