Incidence and incidence trends of the most frequent cancers in adolescent and young adult Americans, including "nonmalignant/noninvasive" tumors.

Background: Incidence rates and trends of cancers in adolescents and young adults (AYAs) ages 15 to 39 years were reexamined a decade after the US National Cancer Institute AYA Oncology Progress Review Group was established.

Methods: Data from the Surveillance, Epidemiology, and End Results program through 2011 were used to ascertain incidence trends since the year 2000 of the 40 most frequent cancers in AYAs, including tumors with nonmalignant/noninvasive behavior.

Results: Seven cancers in AYAs exhibited an overall increase in incidence; in 4, the annual percent change (APC) exceeded 3 (kidney, thyroid, uterus [corpus], and prostate cancer); whereas, in 3, the APC was between 0.7 and 1.4 (acute lymphoblastic leukemia and cancers of the colorectum and testis). Eight cancers exhibited statistically significant decreases in incidence among AYAs: Kaposi sarcoma (KS), fibromatous neoplasms, melanoma, and cancers of the anorectum, bladder, uterine cervix, esophagus, and lung, each with an APC less than -1. AYAs had a higher proportion of noninvasive tumors than either older or younger patients.

Conclusions: An examination of cancer incidence patterns in AYAs observed over the recent decade reveal a complex pattern. Thyroid cancer by itself accounts for most of the overall increase and is likely caused by overdiagnosis. Reductions in cervix and lung cancer, melanoma, and KS can be attributed to successful national prevention programs. A higher proportion of noninvasive tumors in AYAs than in children and older adults indicates a need to revise the current system of classifying tumors in this population.