NONMELANOMA SKIN-CANCER AND SOLAR KERATOSES .1. METHODS AND DESCRIPTIVE RESULTS OF THE SOUTH WALES SKIN-CANCER STUDY

This study aimed to describe the prevalence and incidence of solar ker atoses and skin cancers and the natural history of solar keratoses in a random population sample. It was a cross-sectional study, with follo w-up. conducted in South Wales, and involved 1034 subjects aged 60 yea rs and over drawn from the Family Health Services Authority register. The main outcome measures were detection of the presence of solar kera toses and skin cancers on sun-exposed skin and photographic validation of solar keratoses and biopsy confirmation of cancers wherever possib le. We found that solar keratosis prevalence was 23% (95% confidence i nterval 19.5-26.5) and that of skin cancer (all types) 2% (95% confide nce interval 1.0-3.5). The incidence rate of solar keratoses was 149 l esions per 1000 person-years and of non-melanoma skin cancer 9 per 100 0 person-years. In all 21% (95% CL 16-26) of solar keratoses regressed spontaneously during follow-up. None underwent malignant change. We b elieve that the failure of individuals to seek medical advice and the variable under-registration of non-melanoma skin cancer makes populati on-based study important. The high prevalence and incidence of maligna nt and pre-malignant skin lesions in this random sample raise major pu blic health concerns. The high rate of spontaneous regression of solar keratoses and the low rate of malignant change challenges conventiona l views about the need for routine treatment of these lesions.