Abstract CN12-04: Prevention of skin cancer: Lessons from “Down Under.”

Abstract

Abstract Physical avoidance of intense/excessive exposure to sunlight is the mainstay of primary prevention of skin cancer. Since such exposure is sometimes unavoidable especially “Downunder,” we have studied adjunct protective measures to prevent basal cell carcinoma (BCC), squamous cell carcinoma (SCC) and melanoma. In a 20-year community study in Queensland adults, the major adjunct measure that has emerged is regular sunscreen application. From 1992 to 1996, 1621 adult residents of the township of Nambour were randomly allocated to the sunscreen intervention: daily sunscreen application to head, neck, arms and hands, or the control arm: usual (discretionary) sunscreen use. (Allocation of a placebo sunscreen to the control group was unethical given the subtropical location.) After the trial, follow-up for primary BCC and SCC continued until 2004 and for melanoma until 2006 and sun exposure was also monitored. Available slides of melanomas were reviewed by two pathologists unaware of sunscreen allocation. No effect on incidence of basal cell carcinoma by sunscreen use was seen but the incidence of squamous-cell carcinoma tumors was significantly lower in the sunscreen intervention group than in the control group (Rate Ratio (RR) 0·61, 0·46–0·81). On follow-up 8 years after the sunscreen intervention ceased, a 35% decrease in overall incidence of SCC persisted in those randomly allocated to the intervention but no significant long-term reductions in incidence of BCC were observed. On follow-up 10 years after trial cessation, a significant reduction in melanoma was observed such that melanoma risk was halved in those allocated to the sunscreen intervention. The amounts of time spent outdoors on weekdays and weekend days were no different between the two trial-treatment groups. Certain dietary factors can also decrease skin cancer incidence, independently of sun exposure and phenotype. In those with past skin cancer, consumption of green leafy vegetables lowered risk of SCC by more than 50%, and dietary patterns characterized by low meat and fat intake similarly lowered SCC risk. In addition, the regular use of non-steroidal anti-inflammatory medications also substantially lowered the risk of SCC development. Thus SCCs appear amenable to prevention in adults by several adjunct means, while evidence regarding practical measures to complement basic sun protection measures for prevention of BCCs and melanoma is more limited. Citation Information: Cancer Prev Res 2010;3(1 Suppl):CN12-04.