Projection of future gastric cancer incidence and health-care service demand by geographic area in Kanagawa, Japan.

Projections of future gastric cancer incidence and the demand for health-care services for gastric cancer patients by geographic area will assist local authorities in determining health-care needs, allocating medical resources, and planning services. This study aims to project the future incidence of gastric cancer, estimate the number of patients per medical institution, and decompose the net changes in cases to assess the impact of population aging by geographic area. Our projections are based on population-based cancer registry data, census data from 2000 to 2020, and the projected population for 2025-2045 in Kanagawa, Japan. We classified Kanagawa into urban, town, outer city, and rural areas based on geographic and population features. The number of medical institutions providing gastric cancer treatment was used to estimate the number of patients per medical institution. We projected a decrease of 25%, 52%, and 5% in gastric cancer cases in towns, outer cities, and rural areas from 2020 to 2045, respectively. However, cases are expected to increase by 9% in urban areas, primarily due to population aging. The annual number of gastric cancer patients per medical institution in urban areas is expected to increase from 54 to 59, while numbers in other areas are predicted to decline from 2020 to 2045. Our long-term projections indicate that the number of older gastric cancer patients will continue to increase in urban areas. While current measures effectively reduce gastric cancer risk, they need to be revised to address the impact of population aging.