Skin cancer risk factors among black South Africans — the Johannesburg Cancer Study, 1995–2016

Abstract Background The Black population is known to have lower risk for skin cancers due to melanin content of the skin. Regardless, skin cancers still occur in Black populations. The aim of this study was to identify risk factors associated with skin cancer among Blacks presenting at selected tertiary hospitals in Johannesburg, South Africa. Methods A case-control study was conducted; cases were patients with keratinocyte cancers (KCs) and/or melanoma skin cancer (MSC) and controls were cardiovascular patients. Socio-demographic exposures (sex and residency), environmental exposures (heating and cooking fuels), smoking, and HIV status were assessed. The proportions of cases by skin cancer major subtype, demographics, histological spectrum and anatomical site of distribution were determined. A stepwise (backward elimination) logistic regression was done to identify risk factors associated with KC and MSC. Results More KCs (n = 160) were found compared to MSCs (n = 101). The majority of both KCs and MSCs were reported in ages 51-60-years (27%). The median age at KC and MSC diagnosis was similar in both sexes; 50-years (IQR:38–57) and 56-years (IQR:48–68), respectively. The KC histological spectrum showed that there were more squamous cell carcinomas (SCCs) (78/160 in females, and 72/160 in males) than basal cell carcinoma (BCC). The SCC lesions were mostly found on the skin of the head and neck in males (51%, 38/72) and on the trunk in females (46%, 36/78). MSC was shown to affect the skin of the lower limbs in both males (68%, 27/40) and females (59%, 36/61). Using females as the reference group, when age, current place of residency, type of cooking fuel used currently, smoking, and HIV status were adjusted for, males had an odds ratio (OR) of 2.04 for developing KC (CI:1.08–3.84, p = 0.028). Similarly, when age, current place of residency, place of cooking (indoors or outdoors) were adjusted for, males had an OR of 2.26 for developing MSC (CI:1.19–4.29, p = 0.012). Conclusions Differences in anatomical distribution of KCs by sex suggest different risk factors between sexes. Rural dwelling was a newly found association to skin cancer and warrants further investigation. This study highlights the importance of skin cancer awareness campaigns and interventions especially in rural areas.