Risk factors for non-melanomatous skin cancer in Alexandria, Egypt

The role of constitutional and environmental factors on the risk of non-melanomatous skin cancer was evaluated in a case-control study conducted in 1992 in Alexandria, Egypt, on 136 incident histologically confirmed (99 basal-cell and 37 squamous-cell) cases of non-melanomatous skin cancer (NMSC) and 145 controls in hospital for a broad spectrum of acute non-sun-related dermatological conditions. In relation to skin colour, compared with brown-skinned subjects, the multivariate relative risks (RR) were 2.3 for olive-skinned subjects and 3.8 for fair/medium-skinned subjects. Three cases and 29 controls were black (RR = 0.2). The trend in risk with skin colour was significant. Likewise, compared with subjects with brown or hazel eyes, those with green or blue eyes had a RR of 3.1. In relation to acute sun reaction, compared with subjects reporting easy tanning, the RRs were 2.5 for subjects reporting moderate tanning and 4.7 for those reporting easy burning. The risk of NMSC was higher for subjects reporting an outdoor occupation than for those reporting an indoor occupation (RR = 7.7). A significant trend in risk was observed with degree of sun exposure: compared with subjects reporting light sun exposure, the RR was 3.0 for those reporting moderate exposure, and 6.1 for those reporting heavy sun exposure. There was an indication of a relationship between clothing pattern and skin-cancer risk: compared with subjects reporting frequent use of traditional Egyptian clothes, the RR for dressing in short clothes was 1.8. The presence of signs of photodamage was also associated with NMSC (RR = 3.7). Exposure to arsenic was reported by 10 cases and 1 control (RR = 9.5). A positive interaction between sun exposure and skin colour was observed, and the RR rose to 14.2 for medium- or fair-skinned subjects with heavy exposure compared with brown- or black-skinned subjects with light or moderate sun exposure. In this Egyptian population, over 60% of NMSC could be attributed to sun exposure and approximately 45% to skin colour.