Case-Control Study Of Sunlight Exposure In Basal And Squamous Cell Carcinomas Of The Skin

Abstract Background: Ultraviolet radiation (UVR) exposure is the most important environmental risk factor for non-melanoma skin cancer (NMSC), comprised of basal (BCC) and squamous (SCC) cell carcinomas. However, the precise relationship between UVR exposure and skin cancer may differ by NMSC type. A case-control study was conducted to evaluate the relationship between patterns and timing of sun exposure and BCC/SCC. Methods: Study participants included histologically confirmed BCC (n=218) and SCC (n=169) cases recruited from a university dermatology clinic and control subjects who underwent a skin cancer screening exam and screened negative for and had no history of cancer (n=316). Information on patterns (intermittent vs. continuous) and timing (childhood vs. adulthood) of sun exposure was obtained from self-administered questionnaires. Associations with BCC/SCC were estimated by odds ratios (OR) and 95% confidence intervals (CI) calculated using logistic regression. Backward stepwise elimination was used to obtain the most parsimonious models that best fit the data. Final main effect models were adjusted for the following factors: age, sex, ethnicity, education, eye and hair color, smoking status, skin sensitivity to sun exposure, sun exposure protection behaviors, and history of dysplastic nevi and actinic keratosis. Results: History of blistering sunburn, a marker of intermittent sun exposure, was significantly positively associated with BCC (OR=2.08, 95% CI=1.19-3.64), but no association was observed with SCC (OR-1.37, 95% CI=0.69-2.69). Compared to reporting no moles on one's forearm, reporting ≥ 10 moles, a marker of increased childhood sun exposure, was positively associated with SCC (OR=5.37, 95% CI=1.11-26.0) but not BCC (OR=0.43, 95% CI=0.07-2.59). High levels of continuous sun exposure (5-6 hours versus <1 hour per day spent continuously during the week and on the weekend) was positively associated with SCC in one's teenage years (OR-5.14, 95% CI=0.63-41.8), twenties (OR=11.7, 95% CI=1.21-141.0), thirties (OR=6.17, 95% CI=1.01-37.8), and the ten years prior to study enrollment (OR=5.12, 95% CI=0.64-41.2). For BCC, associations with high levels of continuous sun exposure were observed in one's twenties (OR=4.80, 95% CI=1.10-21.0) and thirties (OR=6.66, 95% CI=1.23-35.4), but similar associations were not observed in one's teenage years (OR=1.29, 95% CI=0.28-5.88) and the past 10 years prior to study enrollment (OR=1.40, 95% CI=0.36-5.49). Conclusions: The associations between UVR and NMSC may differ by patterns and timing of sun exposure. Specifically, intermittent sun exposure appears to be associated with BCC and chronic sun exposure with SCC. Additionally, we observed sunlight exposure in adulthood to be associated with BCC while lifetime sun exposure was associated with SCC, in our study population. Citation Format: {Authors}. {Abstract title} [abstract]. In: Proceedings of the 102nd Annual Meeting of the American Association for Cancer Research; 2011 Apr 2-6; Orlando, FL. Philadelphia (PA): AACR; Cancer Res 2011;71(8 Suppl):Abstract nr 1881. doi:10.1158/1538-7445.AM2011-1881