Cigarette Smoking and the Risks of Basal Cell Carcinoma and Squamous Cell Carcinoma.

Sunlight is the principal environmental risk factor for keratinocyte cancers, but other carcinogens have also been implicated, including tobacco smoke. Findings have been conflicting, however. We investigated associations between cigarette smoking and incidence of basal cell carcinoma (BCC) or squamous cell carcinoma (SCC) in QSkin, a prospective study of skin cancer (N = 43,794). Smoking history was self-reported at baseline; newly diagnosed BCCs and SCCs were ascertained through data linkage and verified by histopathology reports. We restricted analyses to white participants who at baseline reported no past history of skin cancer excisions and no more than five destructively treated actinic skin lesions. We fitted Cox proportional hazards models, adjusted for known confounders. Compared with never smokers, current smokers had significantly lower risks of BCC (hazard ratio = 0.6; 95% confidence interval = 0.4-0.9) but significantly higher risks of SCC (hazard ratio = 2.3; 95% confidence interval = 1.5-3.6). Former smokers had similar risks for BCC and SCC as never smokers. Among smokers, we observed no dose-response trends with duration of smoking, intensity, or time since quitting. On further analysis, current smokers had fewer skin examinations and procedures than never smokers, suggesting greater opportunities for detection among never smokers. Strengths include large sample size, prospective design, and virtually complete follow-up; however, histologic details were missing for a proportion of excised tumors. In conclusion, current smokers had a lower incidence of BCC (possibly because of detection bias) but higher rates of SCC.

Anatomical Distributions of Basal Cell Carcinoma and Squamous Cell Carcinoma in a Population-Based Study in Queensland, Australia.

IMPORTANCE: Keratinocyte cancers (KCs), including basal cell carcinoma (BCC) and squamous cell carcinoma (SCC), are the most common cancers among fair-skinned populations worldwide. Although studies have indicated that the anatomical distribution of BCC and SCC differ, few have compared them directly in well-defined population samples. OBJECTIVES: To describe and compare the anatomical distribution of BCC and SCC in a population-based sample in Queensland, Australia. DESIGN, SETTING, AND PARTICIPANTS: This study was nested within the population-based QSkin Sun and Health Study in Queensland, Australia. Of 37 103 study participants linked to national medical insurance records, 3398 diagnosed with KCs from September 1, 2010, to September 30, 2012, were identified, and information about their KCs was extracted from pathology reports. Data were analyzed from January 1, 2013, to March 30, 2016. MAIN OUTCOMES AND MEASURES: The relative tumor densities (RTDs) on defined body sites, calculated by dividing the proportion of tumors occurring at a specified site by the proportion of skin area of that site. RESULTS: A total of 5150 KCs with complete data were identified in 2374 study participants (1339 men [56.4%] and 1035 women [43.6%]; mean [SD] age, 59.7 [7.4] years). Of these, 3846 KCs (74.7%) were BCCs. Most BCCs were on the head and/or neck (1547 [40.2%]) and the trunk (1305 [33.9%]); most SCCs were on the head and/or neck (435 [33.4%]) and upper limbs (455 [34.9%]). The greatest differences in RTDs between BCC and SCC were on the hand (BCC:SCC ratio, 1:14) and the back and/or buttocks (BCC:SCC ratio, 8:1). Relative tumor densities of KCs were higher on the scalp and ear in men compared with women, and on the upper arm in women compared with men. The pattern of RTDs did not differ with age for BCC. Compared with younger adults (40-54 years), the RTDs in older adults (55-69 years) were 2-fold higher for SCC on the scalp (0.38 [95% CI, 0.00-0.81] vs 1.07 [95% CI, 0.75-1.38]) and the back and/or buttocks (0.05 [95% CI, 0.00-0.12] vs 0.12 [95% CI, 0.07-0.16]). CONCLUSIONS AND RELEVANCE: The high RTDs on sun-exposed body sites for BCC and SCC are in keeping with sun exposure as the primary etiologic factor for both tumors. However, for BCC, the low RTD on the hand and high RTDs on less sun-exposed sites suggest a complex association between sun exposure and occurrence of BCC. Knowledge about the anatomical distribution of BCC and SCC may provide insight into their diagnoses and causes.

Medicare claims data reliably identify treatments for basal cell carcinoma and squamous cell carcinoma: a prospective cohort study.

OBJECTIVE: To investigate the accuracy of Medical Benefit Schedule (MBS) item numbers to identify treatments for basal cell carcinomas (BCC) and squamous cell carcinomas (SCC). METHODS: We linked records from QSkin Study participants (n=37,103) to Medicare. We measured the proportion of Medicare claims for primary excision of BCC/SCC that had corresponding claims for histopathology services. In subsets of participants, we estimated the sensitivity and external concordance of MBS item numbers for identifying BCC/SCC diagnoses by comparing against 'gold-standard' histopathology reports. RESULTS: A total of 2,821 (7.6%) participants had 4,830 separate Medicare claims for BCC/SCC excision; almost all (97%) had contemporaneous Medicare claims for histopathology services. Among participants with BCC/SCC confirmed by histology reports, 76% had a corresponding Medicare claim for primary surgical excision of BCC/SCC. External concordance for Medicare claims for primary BCC/SCC excision was 68%, increasing to 97% when diagnoses for intra-epidermal carcinomas and keratoacanthomas were included. CONCLUSIONS: MBS item numbers for primary excision of BCC/SCC are reasonably reliable for determining incident cases of keratinocyte skin cancers, but may underestimate incidence by up to 24%. IMPLICATIONS: Medicare claims data may have utility in monitoring trends in conditions for which there is no mandatory reporting.