Cost of illness in a super-aged society-comparison of breast, lung, and prostate cancer in Japan.

Background: Aging increases the disease burden because of an increase in disease prevalence and mortality among older individuals. This could influence the perception of the social burden of different diseases and treatment prioritization within national healthcare services. Cancer is a disease with a high disease burden in Japan; however, the age-specific frequency and age-specific mortality rates differ according to site. In this study, we evaluated the relationship between the aging of the Japanese society and the disease burden by comparing the features of three cancers with different age-specific frequency rates in Japan. Furthermore, we made projections for the future to determine how the social burden of these cancers will change.

Methods: We calculated the social burden of breast, lung, and prostate cancers by adding the direct, morbidity, and mortality costs. Estimates were made using the cost of illness (COI) method. For future projections, approximate curves were fitted for mortality rate, number of hospital admissions per population, number of outpatient visits per population, and average length of hospital stay according to sex and age.

Results: The COI of breast, lung, and prostate cancers in 2017 was 903.7, 1,547.6, and 390.8 billion yen, respectively. Although the COI of breast and prostate cancers was projected to increase, that of lung cancer COI was expected to decrease. In 2017, the average age at death was 68.8, 76.8, and 80.7 years for breast, lung, and prostate cancers, respectively.

Conclusions: Patients with breast cancer die earlier than those with other types of cancer. The COI of breast cancer ("young cancer") was projected to increase slightly because of an increase in mortality costs, whereas that of prostate cancer ("aged cancer") was projected to increase because of an increase in direct costs. The COI of lung cancer ("aging cancer") was expected to decrease in 2020, despite the increase in deaths, as the impact of the decrease in human capital value outweighed that of the increase in deaths. Our findings will help prioritize future policymaking, such as cancer control research grants.