Cost of illness for colorectal cancer in Japan - a time trend and future projections (1996–2035) based on governmental statistics

BACKGROUND: In Japan, the crude mortality rate of colorectal cancer is the second highest among men and highest among women by site. We aimed to calculate the social burden of colorectal cancer using the cost of illness (COI) method and identify the main factors that drove changes in the COI. METHODS: From 1996 to 2020, the COI was estimated by summing direct, morbidity, and mortality costs. In addition, the COI by 2035 was projected by fitting approximate curves obtained from historical data to health-related indicators by sex and age. Future projections of the number of patients by the stage of disease were also made to explore the factors that changed the COI. RESULTS: The number of deaths and incidence from colorectal cancer was expected to continue increasing due to population aging. However, the COI was projected to rise from 850.3 billion yen in 1996 to 1.451 trillion yen in 2020, and peaked at 1.478 trillion yen in 2023 before it declined. CONCLUSION: Although the increased number of deaths associated with population aging increased COI, it was expected that the COI would decrease around 2023 due to a decrease in the human capital value of the deceased. In addition, the mortality rate was expected to decrease in the future due to an increase in the percentage of early detection of colorectal cancer via widespread screening and advances in medical technology.