Validity of the Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) tool in a Dutch cohort of transplant recipients

Abstract Background To identify patients with high risk of skin cancer, risk prediction tools have been developed. Objectives External validation of the Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) in a Dutch cohort of solid organ transplant recipients (SOTR) and exploration of the possibility of incorporating additional risk factors to enhance its predictive performance. Methods We used data from the ongoing, prospective TransplantLines Biobank and Cohort Study of the University Medical Center Groningen (Groningen, The Netherlands). We conducted a survival analysis using Fine and Gray models to determine the subdistribution hazard ratios of the SUNTRAC risk factors and groups, Wolbers C index to assess its discriminative power, and cumulative incidences of skin cancer to assess its calibration. We applied the same methods for the incorporation of additional risk factors to the model. Results A total of 2099 patients were included with a median age at transplantation of 52.1 years (Interquartile range [IQR]: 40.6–60.1) and a median follow‐up time of 6.6 years (IQR: 3.4–12.5). In total 478 (22.8%) patients developed skin cancer. Basal cell carcinoma (53.3%) and cutaneous squamous cell carcinoma (42.9%) were most prevalent. The cumulative incidences of skin cancer per SUNTRAC risk group at 10 years were: low‐risk (1.8%), medium‐risk (12.9%), high‐risk (34.3%) and very high‐risk (68.6%). Significantly different skin cancer risk rates were observed for the medium‐risk (SHR = 9.9, 95% CI: 2.51–39.4), high‐risk (SHR = 21.5, 95% CI: 5.40–85.2) and very high‐risk (SHR = 80.3, 95% CI: 19.26–335.1) groups in reference to the low‐risk group. Wolbers C‐index at 5 years was 0.71. The model was well calibrated for our cohort. The addition of other potential risk factors yielded no or marginal improvement of discriminative value on top of SUNTRAC. Conclusions SUNTRAC is valid for the general Dutch SOTR population, and it can be clinically implemented.