Risk factors for single and multiple basal cell carcinomas.

OBJECTIVE: To investigate the incidence of single and multiple basal cell carcinoma (BCC) lesions and associated risk factors.

DESIGN: A prospective, population-based cohort study (from January 1, 1990, through December 31, 2007).

SETTING: Two cohorts of 10 994 Dutch people, 55 years or older, were studied in 1990 (first cohort) and 1999 (second cohort).

PATIENTS: Patients with BCC lesions were identified from the Dutch national pathology laboratories network, hospitals, and general practices.

MAIN OUTCOME MEASURES: The associations between determinants and single and multiple BCC lesions were studied by estimating odds ratios (ORs) and hazards ratios, using multivariate logistic regression and Andersen-Gill models, respectively.

RESULTS: Of the eligible 10 820 cohort members, 524 (4.8%) had BCC, of whom 361 had single and 163 (31.1%) had multiple lesions. Age and red hair were significant risk factors for a first BCC lesion in a multivariate model. In the Andersen-Gill model, people who developed a first BCC lesion after 75.0 years of age were significantly less likely to develop multiple lesions (> or =75.0 years adjusted OR, 0.58; 95% confidence interval [CI], 0.47-0.71). Red hair (adjusted OR, 1.43; 95% CI, 1.05-1.94), high educational level (1.42; 1.12-1.81), and a first BCC lesion located on the upper extremities (1.49; 1.02-2.15) were associated with a significantly increased risk of developing multiple lesions.

CONCLUSION: Patients who are relatively young at their first BCC diagnosis, those with red hair, those with higher socioeconomic status, and/or those with a BCC lesion on their upper extremities have a higher risk of developing multiple lesions and require closer follow-up over time.