Subsequent primary neoplasm risk among survivors of cancer in adolescence and young adulthood: a population-based study from Alberta, Canada

Background: Survivors of cancer in adolescence and young adulthood are at increased risk for subsequent primary neoplasms, but studies using Canadian data are limited. We sought to quantify the risk of subsequent primary neoplasms among survivors of cancer in adolescence and young adulthood in Alberta, Canada. Methods: The Alberta Adolescent and Young Adult Cancer Survivor Study is a retrospective, population-based cohort of people aged 15 to 39 years with a neoplasm first diagnosed between 1983 and 2017. We assessed risks of subsequent primary neoplasms overall and after 5-year survival, calculated as standardized incidence ratios (SIRs) and absolute excess risks (AERs) per 10 000 person-years, compared with expected general population rates, with up to 30 years of follow-up. Results: Among 24 459 people who had cancer in adolescence and young adulthood, 1442 had subsequent primary neoplasms, 1129 of which occurred after 5-year survival. The risk of subsequent primary neoplasm overall and after 5-year survival was similar (SIR 2.2, 95% confidence interval CI 2.1 to 2.4 v. 2.0, 95% CI 1.9 to 2.2; AER 31.7, 95% CI 28.7 to 34.6 v. 35.7, 95% CI 31.6 to 39.8 per 10 000 person-years). Most subsequent primary neoplasms were breast, digestive, hematopoietic, or respiratory cancers. After 5-year survival, the 30-year cumulative incidence of a subsequent primary neoplasm was 17.7% (95% CI 16.5% to 18.9%), with incidence highest among survivors of cancers of the oral cavity, lip, or pharynx (28.9%, 95% CI 18.9% to 39.6%), breast cancer (27.3%, 95% CI 23.7% to 30.9%), colon cancer (23.5%, 95% CI 14.2% to 34.1%), and Hodgkin lymphoma (22.7%, 95% CI 18.2% to 27.6%). Interpretation: Survivors of cancer in adolescence and young adulthood are at increased risk for nearly all types of subsequent primary neoplasms assessed. Early, risk-based screening may be warranted, particularly for screen-detectable cancers for which risks are greatest.