Risk of secondary nonhematologic malignancies after allogeneic stem cell transplantation: A nationwide case-control cohort study

Our study investigated the incidence of secondary nonhematologic malignancies in patients undergoing allogeneic hematopoietic stem cell transplantation (allo-SCT) and explored its risk compared to the general population. A population-based case cohorts with adult patients who received allo-SCT between January 2002 and December 2018 and a control cohort with matched general population were extracted from the Korean National Health Insurance Service database. Each case and control cohort included 5177 patients. With a median follow-up of 2374 days for the case cohort and 2269 days for the control cohort, the 10-year cumulative incidence rate of nonhematologic malignancy was significantly higher in the case cohort compared to the control cohort (4.23% vs 2.3%, hazard ratio [HR] 1.73, 95% confidence interval [CI] 1.32-2.25, P <.001). The sub-class analysis according to cancer-site revealed significantly higher risks of 10-year cumulative incidence for cancers of head, neck and esophagus (HR 3.19, 95% CI 1.34-7.59, P =.003); cancers involving upper gastrointestinal tract (HR 3.74, 95% CI 1.58-8.85, P <.001), colorectal cancer (HR 2.02, 95% CI 1.04-3.91, P =.029), thyroid cancer (HR 2.09, 95% CI 1.1-3.97, P =.012), gynecological cancer (HR 2.69, 95% CI 1.04-6.96, P =.048) in the case cohort compared to the control cohort. No significant differences were detected for cancers involving lung, mediastinum and heart, breast cancer in female, cancers of the hepatobiliary and pancreatic system and cancers associated with urological system. These findings suggest the need for enhanced screening for nonhematologic malignancies in allo-SCT recipients compared to the general population.