Increased risk of second malignant neoplasms in adolescents and young adults with cancer.

BACKGROUND: The authors describe the incidence and characteristics of secondary malignant neoplasms (SMNs) in adolescent and young adult (AYA) cancer survivors compared with those in younger and older cancer survivors. METHODS: Children aged ≤ 14 years, AYAs aged 15 to 39, and older adults aged ≥ 40 years at the time of primary diagnosis who were reported as cancer survivors in the Surveillance, Epidemiology, and End Results (SEER) program between 1973 and 2011 were compared in this population-based analysis. The primary analysis was the risk that an SMN would occur ≥ 5 years after the original diagnosis for patients who had the more common AYA cancers (leukemia, lymphoma, testicular malignancy, ovarian malignancy, melanoma, and cancers of the thyroid, breast, soft tissue, or bone). The standardized incidence ratio (SIR), absolute excess risk (AER), and cumulative incidence of SMN for the selected cancers were assessed. The risk of SMN for the entire cohort also was analyzed. RESULTS: Of the 148,558 AYA survivors who were diagnosed with a selected cancer, 7384 developed an SMN 5 years after their original diagnosis. The SIRs (95% confidence intervals [CIs]) were 1.58 (95% CI, 1.55-1.62) for AYAs, 4.26 (95% CI, 3.77-4.80) for children, and 1.10 (95% CI, 1.09-1.11) for older adults, and the AERs were 22.9, 16.6, and 14.7, respectively. The cumulative incidence of SMN at 30 years was 13.9% for the AYA group. The most common SMNs in AYAs were breast cancer, gastrointestinal cancer, genital cancers, and melanoma. AYAs who had received radiation therapy had a higher cumulative incidence of SMN. CONCLUSIONS: AYAs who survive cancer for more than 5 years have a higher relative risk of SMN compared with the general population and have a higher absolute risk of SMN compared with younger or older cancer survivors.