Cancer Prevalence Projections in Japan and Decomposition Analysis of Changes in Cancer Burden, 2020-2050: A Statistical Modeling Study

Background: We provide comprehensive sex-stratified projections of cancer prevalence for 22 cancer sites in Japan from 2020 to 2050.Methods: Using a scenario-based approach, we projected cancer prevalence by combining projected incidence cases and survival probabilities. Age-specific incidences were forecasted using age-period-cohort models, while survival rates were estimated using a period-analysis approach and multiple parametric survival models. To understand changes in cancer prevalence, decomposition analysis was conducted, assessing the contributions of incidence, survival, and population demographics.Results: By 2050, cancer prevalence in Japan is projected to reach 3,665,900 (3,210,200 to 4,201,400) thousand cases, representing a 13.1% increase from 2020. This rise is primarily due to a significant increase in female survivors (+27.6%) compared with a modest increase in males (+0.8%), resulting in females overtaking males in prevalence counts from 2040 onward. In 2050, the projected most prevalent cancer sites in Japan include colorectal, female breast, prostate, lung, and stomach cancers, accounting for 66.4% of all survivors. Among males, the highest absolute increases in prevalence are projected for prostate, lung, and malignant lymphoma cancers, while among females, the highest absolute increases are expected for female breast, colorectal, and corpus uteri cancers.Conclusions: These findings emphasize the evolving cancer prevalence, influenced by aging populations, changes in cancer incidence rates, and improved survival. Effective prevention, detection, and treatment strategies are crucial to address the growing cancer burden.Impact: This study contributes to comprehensive cancer control strategies and ensures sufficient support for cancer survivors in Japan.