IMPORTANCE: While a high risk of nonmelanoma skin cancer is well recognized in solid-organ transplant recipients, the risk of skin cancer in hematopoietic stem-cell transplant (HSCT) recipients has not been extensively studied.

OBJECTIVE: To determine the risk of cutaneous cancer in HSCT recipients and compare it with the risk in renal transplant recipients (RTRs) and individuals who have not received any transplant.

DESIGN, SETTING, AND PARTICIPANTS: A nationwide population-based cohort study from the Danish National Hospital Register including 3302 patients who underwent HSCT (1007 allogeneic, 2295 autologous) from 1999 through 2014, 4789 RTRs from 1976 through 2014, and 10 age- and sex-matched nontransplanted individuals for each of the groups from the background population. Person-years at risk were calculated from the time of study inclusion until first cutaneous cancer. To compare the risk of skin cancer between transplant recipients and background population, we used a stratified proportional hazard regression model for hazard ratio (HR) estimations. By use of the cumulative incidence, we estimated 5- and 10-year risks of skin cancers. All RTR and HSCT recipients were treated and followed up in specialized hospital departments in Denmark (total population 5.7 million).

MAIN OUTCOMES AND MEASURES: Primary outcomes were time to first appearance of basal cell carcinoma (BCC), squamous cell carcinoma (SCC), or malignant melanoma (MM) and comparative risk estimates of cutaneous cancers in HSCT recipients and RTRs. The hypothesis was tested during data collection.

RESULTS: Allogeneic HSCT recipients had an increased risk of BCC, SCC, and MM, with respective HRs of 3.1 (95% CI, 1.9-5.2), 18.3 (95% CI, 4.1-81.8), and 5.5 (95% CI, 1.7-17.7) compared with the background population. Compared with RTRs, allogeneic HSCT recipients had a 3-fold higher risk of MM. The risk of BCC after allogeneic HSCT was seen only in patients conditioned with total-body irradiation (HR, 3.9 [95% CI, 2.6-6.8]). The risk of BCC was similar for allogeneic HSCT recipients and RTRs, while the risk of SCC was highest for RTRs. Autologous HSCT recipients had no increased risk of skin cancer.

CONCLUSIONS AND RELEVANCE: Allogeneic HSCT recipients have an increased risk of BCC, SCC, and MM. Total-body irradiation was a major determinant for BCC. Our findings indicate the relevance of dermatologic follow-up in HSCT recipients.