A DOSE-RESPONSE CURVE FOR SUN EXPOSURE AND BASAL-CELL CARCINOMA

A population-based case-control study of sun exposure and basal cell c arcinoma (BCC) was conducted in Western Australia in 1988. Its aim was to examine the relationship between risk of BCC and the amount and pa ttern of sun exposure. This report deals with amount of exposure. The odds ratios (ORs) for BCC on the head and neck and limbs decreased wit h increasing total exposure, whereas the opposite was observed for BCC on the less heavily exposed trunk, with the highest OR in those with the greatest exposure. In an analysis of all body sites together in wh ich the total hours of exposure to the specific site was treated as a continuous variable, an initial rise in risk of BCC was seen with a pe ak OR of 1.4 at about 35,000 hr of exposure, followed by a fall. In co ntrast to these site-specific patterns, lifetime accumulated sun expos ure of the whole body showed no appreciable association with BCC eithe r in total or for working days only. Risk of BCC was positively associ ated with lifetime exposure on non-working days, however, with an OR f or higher than baseline categories of around 1.7. There was a signific ant interaction between ability to tan and total and occupational sun exposure. Risk increased with increasing exposure in those who tanned well but not in those who tanned poorly. This pattern is consistent wi th other observations which indicate that beyond a certain level of su n exposure risk of BCC does not increase further. (C) 1995 Wiley-Liss, Inc.