Body site specific incidence of basal and squamous cell carcinoma in an exposed population, Townsville, Australia.

Most data on body site distribution of basal cell carcinoma (BCC) and squamous cell carcinoma (SCC) do not take into account the surface proportion occupied by body sites experiencing differing amounts of ultraviolet radiation. The recording of BCC and SCC is heterogenous and body sites are not standardized. This study was undertaken to assess the magnitude of the incidence rates of skin cancers at different body sites in a population which experiences high ultraviolet exposure and involved all primary care services in Townsville over 6 weeks in June 1993. The annual site-specific age-standardized (World Population) incidence rates of histologically diagnosed lesions, determined from data where lesions were recorded on a body map, were adjusted for surface area and expressed per 100,000 body units (BU). Relative site densities of lesions were also calculated. Annual incidence rates for BCC per 100,000 BU on the most exposed face (ears, nose and cheeks) were 25,893 (95% confidence interval (c.i.) 18,837-32,950), 13,222 (95% c.i., 8273-18,171) on the less exposed face (forehead,eyebrow, chin and jaw) and 27,837 (95% c.i., 12,560-43,115) on the least exposed face (area within the orbit and nasolabial fold). Incidence rates for SCC rates were highest on the less exposed face, 5843 (95% c.i., 2627-9058) most exposed face, 4200 (95% c.i., 1274-7126) and the exposed upper limb, 3786 (95% c.i., 2783-4789). The relative site density of histologically confirmed BCC was 14 on the most exposed face in males compared with 5 in females and 11 around the eyes (least exposed) in males and 9 in females compared with the body as a whole. Adjustment for body surface proportion demonstrates that highly exposed body sites are at very high risk. The magnitude of the incidence rates on these sites is attributed to the combination of a susceptible population and high ambient ultraviolet radiation (UVR).