Multiple primary cancers in survivors of adolescent and young adult cancers in the United States, SEER 1973-2012

Despite improvements in cancer survival rates, cancer survivors have an increased risk for a number of health issues including the development of multiple primary cancers (MPCs). MPCs have been well-studied in childhood and adult cancer survivors, but the risk of developing MPCs is not well-characterized in survivors of adolescent and young adult (AYA) cancers. Additionally, the role of survival from MPCs in AYA cancers has not yet been examined. The present study utilized data from the Surveillance, Epidemiology, and End Results (SEER) registries (1973-2012) to assess the risk for MPCs and survival after a second primary cancer (SPC) in survivors of AYA cancers. Individuals diagnosed with a first primary cancer between the ages of 15 and 39 were included in this study. Overall and site-specific standardized incidence ratios (SIR) and excess absolute risks (EAR) were assessed, and multivariable Poisson regression models were used to assess the risk for MPCs over time. Kaplan-Meier and Cox proportional hazards modeling were utilized to assess survival after a SPC. Out of 227,569 AYA survivors, 15,069 (6.6%) developed a MPC two or more months after the first primary cancer. Survivors of AYA cancers had a nearly 2-fold increased risk of developing an MPC (SIR=1.86, 95% CI 1.84-1.89). The most common MPCs in AYAs were breast cancer, digestive system cancers, and skin cancers. Age at first cancer diagnosis, gender, race, radiation treatment, type of first primary cancer, and latency were significantly associated with the development of a MPC. We observed females had a reduced risk for death compared to males (HR=0.73, 95% CI 0.68-0.78) after a SPC, and Blacks had an increased risk for death after a SPC compared to Whites (HR=1.23, 95% CI 1.18-1.38). Our findings indicate that AYA cancer survivors are at higher risk for multiple primary cancers and provide new knowledge of the survival from second primary cancers in the AYA population. We observed that males and Blacks have a worse prognosis after the development of a subsequent cancer. This may have direct implications on the clinical management and prevention strategies for AYA cancer survivors.