Cancer in adolescents and young adults: National incidence and characteristics in Japan

Objective: Adolescents and young adults (AYA) with cancer are confronted with unique challenges in areas of paramount concern within their age group, such as fertility, education, career, and delayed and long-term effects of treatment. However, the extent and depth of the problem has never been examined in the Japanese population. The aim of this study was to describe the status of cancer patients in the AYA population, using data from the hospital-based cancer registry (HBCR). Study design: Patients included in the HBCR from January 2011 to December 2014 were included in this study to evaluate the incidence and cancer distribution trends among AYA. The total number and the proportion of AYA (15-39 years of age) stratified by sex, age, and cancer type were obtained. The incidence of age-specific cancer among AYA was also calculated. Results: We identified 30,394 male (35.1%) and 56,100 female (64.9%) cancer patients in the population, which collectively constituted about 3% of all invasive cancer cases. The incidence of cancer in AYA was estimated as 86.2 per 100,000 per year, and increased with age. The most affected population was women between 35 and 39 years of age (35%). Breast cancer was the most common type of cancer, followed by cervical, uterine, and thyroid cancers. Conclusion: A substantial number of AYA are diagnosed with cancer every year. The distribution of cancer types in AYA was dependent on age and sex. These diversities in cancer types can inform researchers and policy makers to fine-tune their studies and policies.