Incidence and Risk Factors of Keratinocyte Carcinoma After First Solid Organ Transplant in Ontario, Canada.

Importance: Keratinocyte carcinoma (KC), also known as nonmelanoma skin cancer, is the most common malignancy after solid organ transplant. Epidemiologic data on posttransplant KC in North America are limited by a lack of KC capture in cancer and transplant registries.

Objective: To estimate the incidence and identify risk factors for posttransplant KC.

Design, Setting, And Participants: This population-based inception cohort study in Ontario, Canada, used linked administrative databases and a health insurance claims-based algorithm. Participants were adult recipients of a first kidney, liver, heart, or lung transplant from January 1, 1994, to December 31, 2012. The cohort (n = 10 198) was followed up to December 31, 2013. Data were analyzed from May 31, 2016, to April 21, 2017.

Exposures: Solid organ transplant with functioning graft.

Main Outcomes And Measures: Age- and sex-adjusted standardized incidence ratio for KC in the transplant cohort was compared with that in the general population. Cumulative incidence of posttransplant KC was estimated using cumulative incidence functions, accounting for the competing risks of death or kidney graft loss. The association between KC and patient-, transplant-, and health services-related factors was evaluated with a multivariable cause-specific hazards model.

Results: A total of 10 198 transplant recipients were included in the study. The median (interquartile range [IQR]) age at transplant was 51 (41-59) years, with most recipients being male (6608 [64.8%]) and white (5964 [58.5%]). Posttransplant KC was diagnosed in 1690 patients (16.6%) after a median (IQR) of 3.96 (1.94-7.09) years, with an incidence rate of 2.63 per 100 patient-years (95% CI, 2.51-2.76). The rate of KC was significantly higher after transplant compared with the general population (standardized incidence ratio, 6.61; 95% CI, 6.31-6.93). The highest 10-year cumulative incidence was in the subsets of patients with a history of pretransplant skin cancer (66.5%), older than 50 years at transplant (27.5% for 51-65 years; 40.5% for >65 years), and of the white race (24.1%). The strongest independent risk factors for KC included older age at transplant (adjusted hazard ratio [aHR], 9.27; 95% CI, 7.08-12.14 for >65 years vs 18-35 years), white vs black race (aHR, 8.50; 95% CI, 4.03-17.91), pretransplant invasive skin cancer (aHR, 4.30; 95% CI, 3.72-4.98), and posttransplant precancerous skin lesions (aHR, 4.32; 95% CI, 3.77-4.95).

Conclusions And Relevance: The incidence of KC appeared to be substantially increased after transplant, particularly in patients who were older at transplant, were white, and had a history of cancerous or precancerous skin tumors; intensified skin cancer screening, education, and early use of chemopreventive interventions may be warranted for these high-risk patient subsets.