External Validation of the Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) in a Large European Solid Organ Transplant Recipient Cohort

Key PointsQuestionIs the Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) tool valid for guiding skin cancer screening in solid organ transplant recipients (SOTRs)? FindingsThis prognostic study found good prognostic discrimination in a European cohort of 3421 SOTRs. The observed skin cancer incidences were similar to those predicted from the US SOTR population for each risk group. MeaningThese findings suggest that the SUNTRAC tool can be transported to different populations to stratify SOTRs into distinct skin cancer risk groups and identify those at a very high risk, opening the door to efficient and effective preventive measures. This prognostic study assesses the Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) tool to validate it in different populations of solid organ transplant recipients. ImportanceThe Skin and UV Neoplasia Transplant Risk Assessment Calculator (SUNTRAC) tool has been developed in the US to facilitate the identification of solid organ transplant recipients (SOTRs) at a higher risk of developing skin cancer. However, it has not yet been validated in populations other than the one used for its creation. ObjectiveTo provide an external validation of the SUNTRAC tool in different SOTR populations. Design, Setting, and ParticipantsThis retrospective external validation prognostic study used data from a prospectively collected cohort of European SOTRs from transplant centers at teaching hospitals in the Netherlands (1995-2016) and Spain (2011-2021). Participants were screened and followed up at dermatology departments. Data were analyzed from September to October 2021. Main Outcomes and MeasuresThe discrimination ability of the SUNTRAC tool was assessed via a competing risk survival analysis, cumulative incidence plots, and Wolbers concordance index. Calibration of the SUNTRAC tool was assessed through comparison of projected skin cancer incidences. Skin cancer diagnoses included squamous cell carcinoma, basal cell carcinoma, melanoma, and Merkel cell carcinoma. ResultsA total of 3421 SOTRs (median age at transplant, 53 [quartile 1: 42; quartile 3: 62] years; 2132 [62.3%] men) were assessed, including 72 Asian patients (2.1%), 137 Black patients (4.0%), 275 Latinx patients (8.0%), 109 Middle Eastern and North African patients (3.2%), and 2828 White patients (82.7%). With a total of 23213 years of follow-up time, 603 patients developed skin cancer. The SUNTRAC tool classified patients into 4 groups with significantly different risks of developing skin cancer during follow-up. Overall, the relative rate for developing skin cancer estimated using subdistribution hazard ratios (SHRs) and using the low-risk group as the reference group, increased according to the proposed risk group (medium-risk group: SHR, 6.8 [95% CI, 3.8-12.1]; P<.001; high-risk group: SHR, 15.9 [95% CI, 8.9-28.4]; P<.001; very-high-risk group: SHR, 54.8 [95% CI, 29.1-102.9]; P<.001), with a concordance index of 0.72. Actual skin cancer incidences were similar to those predicted by the SUNTRAC tool (5-year skin cancer cumulative incidence for medium-risk group: predicted, 6.2%; observed, 7.0%). Conclusions and RelevanceThe findings of this external validation prognostic study support the use of the SUNTRAC tool in European populations for stratifying SOTRs based on their skin cancer risk and also detecting patients at a high risk of developing skin cancer. This can be helpful in prioritizing and providing better screening and surveillance for these patients.