Purpose: To examine cancer incidence patterns among adolescents and young adults in the United States.
Methods: Cancer incidence data from 26 population-based central cancer registries for 1992-1997 were used. Individual cancers were grouped into specific diagnostic groups and subgroups using an integrated classification scheme. The integrated scheme was developed for this study and was based on the most commonly used schemes in population-based epidemiologic studies: Surveillance, Epidemiology, and End Results Program's site groups, International Classification of Childhood Cancer, and International Agency for Research on Cancer's Histological Groups for Comparative Studies. Percent distributions and age-specific incidence rates per million population were computed for adolescents (aged 15-19 years) and young adults (aged 20-24 years) by gender.
Results: The data for 26,010 cancer cases were examined. Among 15-19-year-olds, the five most common cancers were Hodgkin's disease, leukemia, cancer in the brain and other nervous system, bone cancer, and non-Hodgkin's disease. Among 20-24-year-olds, the five most common cancers were Hodgkin's disease, testicular cancer, thyroid cancer, melanoma of the skin, and leukemia. The proportions and rates of the histologic subtypes for most of the common cancers changed with advancing age. For example, among 15-19-year-olds, acute lymphocytic leukemia accounted for approximately 60% of leukemias in males and 50% in females. Among 20-24-year-olds, however, the corresponding percentages of acute lymphocytic leukemia were 37% in males and 31% in females. For ovarian cancer, the germ cell tumor was the most common subtype (54.6% of all ovarian cancers) among 15-19-year-olds. In contrast, ovarian carcinoma was the predominant subtype (70.4%) among 20-24-year-olds. For both age groups, the incidence rates of nodular Hodgkin's disease, melanoma of the skin, and thyroid cancer were significantly greater in females than in males.
Conclusions: Cancer incidence patterns among adolescents and young adults are distinctive. In these age groups, a transition from predominantly pediatric histologic subtypes to adult subtypes was observed for Hodgkin's disease, leukemia, ovarian cancer, and soft tissue sarcoma. Gender differences were found for Hodgkin's disease, melanoma of the skin, and thyroid cancer.