Long-term Change in the Risk of Skin Cancer After Organ Transplantation: A Population-Based Nationwide Cohort Study.

Importance: The high risk of skin cancer after organ transplantation is a major clinical challenge and well documented, but reports on temporal trends in the risk of posttransplant cutaneous squamous cell carcinoma (SCC) are few and appear contradictory. Objective: To study temporal trends for the risk of skin cancer, particularly SCC, after organ transplantation. Design, Setting, and Participants: Population-based, nationwide, prospective cohort study of 8026 patients receiving a kidney, heart, lung, or liver transplant in Norway from 1968 through 2012 using patient data linked to a national cancer registry. The study was conducted in a large organ transplantation center that serves the entire Norwegian population of approximately 5.2 million. Exposures: Receiving a solid organ transplant owing to late-stage organ failure, followed by long-term immunosuppressive treatment according to graft-specific treatment protocols. Main Outcomes and Measures: Occurrence of first posttransplant SCC, melanoma, or Kaposi sarcoma of the skin. Risk of skin cancer was analyzed using standardized incidence ratios (SIRs) and, for SCC, multivariable Poisson regression analysis of SIR ratios, adjusting for 5-year time period of transplantation, different follow-up time, age, sex, and type of organ. Results: The study cohort included 8026 organ transplant recipients, 5224 men (65.1%), with a mean age at transplantation of 48.5 years. Median follow-up time was 6.7 years per recipient; total follow-up time, 69 590 person-years. The overall SIRs for SCC, melanoma, and Kaposi sarcoma were 51.9 (95% CI, 48.4-55.5), 2.4 (95% CI, 1.9-3.0), and 54.9 (95% CI, 27.4-98.2), respectively. In those who underwent transplantation in the 1983-1987 period, the unadjusted SIR for SCC was 102.7 (95%, 85.8-122.1), declining to 21.6 (95% CI, 16.8-27.0) in those who underwent transplantation in the 2003-2007 period. Adjusting for different follow-up times and background population risks, as well as age, graft organ, and sex, a decline in the SIR for SCC was found, with SIR peaking in patients who underwent transplantation in the 1983-1987 period and later declining to less than half in patients who underwent transplantation in the 1998-2002, 2003-2007, and 2008-2012 periods, with the relative SIRs being 0.42 (95% CI, 0.32-0.55), 0.31 (95% CI, 0.22-0.42), and 0.44 (95% CI, 0.30-0.66), respectively. Conclusions and Relevance: The risk of SCC after organ transplantation has declined significantly since the mid-1980s in Norway. Less aggressive and more individualized immunosuppressive treatment and close clinical follow-up may explain the decline. Still, the risk of SCC in organ transplant recipients remains much higher than in the general population and should be of continuous concern for dermatologists, transplant physicians, and patients.