LONG-TERM EPIDEMIOLOGICAL TRENDS IN LUNG AND GASTRIC CANCER IN THE REPUBLIC OF KAZAKHSTAN

Abstract

Relevance: Lung and gastric cancers remain major contributors to cancer burden in Kazakhstan. Long-term analysis of incidence and stage at diagnosis can guide cancer-control planning. The study aimed to characterize trends in lung and gastric cancer incidence and stage distribution and forecast trends through 2035. Materials and Methods: This retrospective time-series analysis used national cancer statistics for 1998-2025. The study began in 1998, the earliest year with complete and comparable national data. Annual cases, population estimates, and stage at diagnosis were extracted from statistical yearbooks. Incidence rates were calculated per 100,000 population. Annual percentage changes (APCs) with 95% confidence intervals (CIs) were used to assess trends. Forecasting models estimated incidence rates and stage IV proportions through 2035. Results: Newly diagnosed cases declined significantly for lung cancer (APC: -0.29%; 95% CI: -0.59 to 0.00; p = 0.026) and gastric cancer (-0.47%; 95% CI: -0.74 to -0.21; p = 0.001), despite population growth (1.31%; 95% CI: 1.21-1.41; p < 0.001). Incidence rates decreased significantly for lung cancer (-1.58%; 95% CI: -1.82 to -1.34; p < 0.001) and gastric cancer (-1.76%; 95% CI: -1.98 to -1.54; p < 0.001). Stage IV diagnosis declined significantly for gastric cancer (-3.24%; 95% CI: -3.59 to -2.90; p < 0.001), but not for lung cancer (-0.23%; 95% CI: -0.75 to 0.28; p = 0.180). In 2025, stage IV disease accounted for 26.5% of lung and 15.5% of gastric cancer cases. Forecasts in-dicated continued declines through 2035. Conclusion: Lung and gastric cancer incidence rates are declining in Kazakhstan, while stage IV diagnosis remains substantial, particularly for lung cancer. These findings support cancer-control planning and targeted early detection.