Subsequent Primary Cancer Risk Among 5-Year Survivors of Adolescent and Young Adult Cancers.

Background: A comprehensive examination of the incidence and mortality of subsequent primary cancers (SPCs) among adolescent and young adult (AYA) cancer survivors in the United States is lacking.

Methods: Cancer incidence and mortality among 170 404 cancer survivors of 5 or more years who were aged 15-39 years at first primary cancer diagnosis during 1975-2013 in 9 Surveillance, Epidemiology, and End Results registries were compared with those in the general population using standardized incidence ratio (SIR), absolute excess incidence (AEI), standardized mortality ratio (SMR), and absolute excess mortality (AEM).

Results: During a mean follow-up of 14.6 years, 13 420 SPC cases and 5008 SPC deaths occurred among survivors (excluding the same site as index cancer), corresponding to 25% higher incidence (95% confidence interval [CI] = 1.23 to 1.27, AEI = 10.8 per 10 000) and 84% higher mortality (95% CI = 1.79 to 1.89, AEM = 9.2 per 10 000) than that in the general population. Overall, SPC risk was statistically significantly higher for 20 of 29 index cancers for incidence and 26 for mortality, with the highest SIR among female Hodgkin lymphoma survivors (SIR = 3.05, 95% CI = 2.88 to 3.24, AEI = 73.0 per 10 000) and the highest SMR among small intestine cancer survivors (SMR = 6.97, 95% CI = 4.80 to 9.79, AEM = 64.1 per 10 000). Type-specific SPC risks varied substantially by index cancers; however, SPCs of the female breast, lung, and colorectum combined constituted 36% of all SPC cases and 39% of all SPC deaths, with lung cancer alone representing 11% and 24% of all cases and deaths, respectively.

Conclusion: AYA cancer survivors are almost twice as likely to die from a new primary cancer as the general population, highlighting the need for primary care clinicians to prioritize cancer prevention and targeted surveillance strategies in these individuals.