Trends and future projections of cervical cancer-related outcomes in Japan: What happens if the HPV vaccine program is not implemented?

Contrary to other developed countries, in Japan, recent years have seen increases in cervical cancer incidence and mortality among young people. However, the human papillomavirus (HPV) vaccine program, a key measure for avoiding cervical cancer, has been virtually suspended. Temporal changes in cervical cancer profiles in this unique situation have not been fully investigated epidemiologically. This study aimed to determine the current status and future trends of the incidence and mortality of cervical cancer and precancerous lesions in Japan. Mortality rates of cervical cancer during 1975-2016 and incidence rates of cervical cancer and cervical intraepithelial neoplasia (CIN) 3 during 1975-2013 were examined using vital statistics and population-based cancer registry data in Japan. Bayesian age-period-cohort analyses were performed to analyze temporal changes of the three cervical cancer-related outcomes. We also calculated projections to 2028 for the three outcomes, assuming that HPV vaccination coverage and screening rates in Japan would be maintained at the current level after the resumption of the national vaccination program. The risk of occurrence of the three outcomes showed similar changes by birth cohort, peaking in the mid-1890s-1900s birth cohorts, declining sharply in the 1940s birth cohort, and persistently increasing in the 1950s and later birth cohorts. Projections to 2028 show increases in cervical cancer incidence and mortality in the 30-69 age group, with a particular increase in CIN3 incidence in the 25-49 age group, if HPV vaccine programs and screening are not effectively implemented. These findings revealed an increasing cervical disease burden among reproductive age females in Japan.