Risk factors for single and multiple basal cell carcinomas

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

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

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

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

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.

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.

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.