A Population-Based Analysis of 30-Year Mortality among Five-Year Survivors of Adolescent and Young Adult Cancer: The Roles of Primary Cancer, Subsequent Malignancy, and Other Health Conditions

SIMPLE SUMMARY: Cancer survivors are at risk for developing serious health problems and dying prematurely. Adolescents and young adults (AYAs, aged 15–39 years at diagnosis) are a unique population challenged with different cancer types and treatment toxicity than other age groups, impaired access to care, financial hardship, and psychosocial distress due to their life stage. Although 85% of AYAs with cancer are alive 5 years after diagnosis, in subsequent years, their survival is consistently lower and declines faster than the general population. However, knowledge regarding why these long-term survivors of AYA cancer die prematurely is incomplete. Therefore, we sought to provide a detailed report of all causes of death in this population, including recurrence of the first cancer, development of a different cancer type, or other health problems. Our results can help inform future research to develop safer cancer treatment and better long-term care that will improve the health and survival of this vulnerable population. ABSTRACT: Despite an aggregate 5-year survival of 85%, many adolescents and young adults (AYAs, 15–39 years old) treated for cancer die prematurely decades later. To develop a more complete understanding of this problem, particularly the role of specific subsequent malignant neoplasms (SMNs), we used the SEER-9 registry to analyze causes of death (COD: Primary cancer, SMN, non-malignant conditions) among 162,317 AYAs diagnosed with first cancer between 1975–2012 and surviving 5 or more years. Cumulative mortality, attributable mortality, standardized mortality ratios (SMRs), and adjusted hazard ratios were determined for each cancer site and COD. At 30 years, cumulative mortality due to primary cancer was matched by that due to all other causes (12.8% 95% CI [12.5%, 13.0%] for primary cancer versus 12.8% [12.5%, 13.1%] for all other causes combined) in the combined cohort, and was overtaken by non-malignant conditions in Hodgkin lymphoma, testicular, cervical/uterine, and thyroid cancers. Overall, SMNs accounted for 20% of malignant deaths, the most common being lung/bronchus (25.6%), colorectal/liver/biliary/pancreas (19.1%), and breast (10.2%). For non-malignant conditions, excess risk was noted overall (SMR 1.37, 95% CI [1.34, 1.40]) and for infectious (1.97 [1.85, 2.10]), renal (1.85 [1.60, 2.13]), cardio/cerebrovascular (1.38 [1.33, 1.43]), and suicide (1.15 [1.04, 1.27]). Racial minorities were at significantly higher risk across all COD. Safer therapy, longitudinal monitoring, and primary/secondary preventive strategies are needed to reduce late mortality in this vulnerable population.