Cumulative incidence estimates for solid tumors after HCT in the CIBMTR and California Cancer Registry

Compared with the general population, hematopoietic cell transplantation (HCT) survivors are at elevated risk for developing solid subsequent neoplasms (SNs). The Center for International Blood and Marrow Transplant Research (CIBMTR) is a key resource for quantifying solid SN incidence following HCT, but the completeness of SN ascertainment is uncertain. Within a cohort of 18 450 CIBMTR patients linked to the California Cancer Registry (CCR), we evaluated the completeness of solid SN data reported to the CIBMTR from 1991 to 2018 to understand the implications of using CIBMTR data alone or combined with CCR data to quantify the burden of solid SNs after HCT. We estimated the cumulative incidence of developing a solid SN, accounting for the competing risk of death. Within the cohort, solid SNs were reported among 724 patients; 15.6% of these patients had an SN reported by CIBMTR only, 36.9% by CCR only, and 47.5% by both. The corresponding cumulative incidence of developing a solid SN at 10 years following a first HCT was 4.0% (95% confidence interval [CI], 3.5-4.4) according to CIBMTR data only, 5.3% (95% CI, 4.9-5.9) according to CCR data only, and 6.3% (95% CI, 5.7-6.8) according to both sources combined. The patterns were similar for allogeneic and autologous HCT recipients. Linking detailed HCT information from CIBMTR with comprehensive SN data from cancer registries provides an opportunity to optimize SN ascertainment for informing follow-up care practices and evaluating risk factors in the growing population of HCT survivors.