Sun habits in kidney transplant recipients with skin cancer: a case-control study of possible causative factors

Organ transplant recipients are frequently affected by skin cancer, which might also be a major cause of long-term mortality. Excessive sun exposure is considered to be a factor in the aetiology, but uncertainty about the importance of this and other proposed risk factors remains. The purpose of this study was to investigate sun behaviour before and/or after the transplantation in kidney transplant recipients with or without cutaneous squamous cell carcinoma. A nested, population-based, case-control study was carried out on 95 kidney transplant recipients who had contracted cutaneous squamous cell carcinoma after the transplantation and on an accurately matched control population of 154 kidney transplanted patients. Information on sun exposure before and after the transplantation, skin type, use of sunbeds, warts, etc., was obtained from a questionnaire which contained 38 detailed questions. The differences between cases and control subjects were not significant for sun exposure before or after the transplantation, sun protective measures, number of sunburns, outdoor occupation, smoking habits or use of sunbeds. Compared to patients with skin type IV, the cutaneous squamous cell carcinoma odds ratio was 3.0 (95% CI = 1.3-7.0) for skin type I + II. Patients with light blond or red hair colour also had a higher odds ratio than those with dark hair, 3.2 (95% CI = 1.2-8.2), and patients with warts after the transplantation had a higher odds ratio than those without, 2.2 (95% CI = 1.2-4.2). In conclusion, poor tanning ability rather than the amount of sun exposure is associated with the development of cutaneous squamous cell carcinoma in kidney transplant recipients and warts appearing after the transplantation indicate increased risk.