Cancer Mortality among US Solid Organ Transplant Recipients: Novel Methodologies to Estimate Cancer Burden using Linked Population-Based Registries

Abstract

Background: The solid organ transplant population has an elevated risk of cancer compared with the general population. Excess risk is largely due to immunosuppression. As this population grows, understanding long-term health risks such as cancer is critical. Population-based estimates of cancer mortality are needed since they measure the downstream outcome following a cancer diagnosis. Furthermore, quantifying deaths attributable to cancer can inform priorities to reduce the cancer burden. Methods: Linked transplant and cancer registry data were used to identify incident cancers and deaths among solid organ transplant recipients in the United States (1987-2014). Population-attributable fractions (PAFs) of deaths due to cancer and corresponding cancer-attributable mortality rates were estimated. Cancer-attributable mortality rates computed using the PAF were compared to cancer-specific mortality rates computing using cause of death (COD). The life-years lost (LYL) to cancer were estimated using two methods: an approach using matching to construct a cancer-free cohort and an approach using Cox proportional hazards regression models. Results: Among 221,962 transplant recipients, 15,012 developed cancer. Thirteen percent of deaths (PAF=13.2%) were attributable to cancer, corresponding to a cancer-attributable mortality rate of 516 per 100,000 person-years. Lung cancer was the largest contributor to mortality (PAF=3.1%), followed by non-Hodgkin lymphoma (NHL, PAF=1.9%), colorectal cancer (PAF=0.7%), and kidney cancer (PAF=0.5%). Overall, the cancer-specific mortality rate lower, 368 per 100,000 person-years. Within 10 years post-transplant, the mean LYL was 0.16 years per transplant recipient and 2.7 years per cancer. Cancer accounted for 1.9% of the total LYL expected in this population. Lung cancer was the largest contributor, accounting for 24% of all LYL, and NHL had the next highest contribution (15%). Conclusions: Cancer is a substantial cause of mortality among solid organ transplant recipients resulting in excess deaths and a shortened lifespan. Lung cancer and NHL are major contributors to the cancer burden including LYL to cancer, highlighting opportunities to reduce cancer mortality through prevention and screening.