Bowen disease and risk of subsequent malignant neoplasms: a population-based cohort study of 1147 patients.

OBJECTIVE To address the long-standing question of whether patients with Bowen disease are at increased risk of internal malignant neoplasms. PATIENTS A total of 1147 Danish patients diagnosed between 1978 and 1993 as having Bowen disease at nongenital sites were followed up for 6463 person-years for cancer occurrence up to 16 years after the skin lesion. MAIN OUTCOME MEASURE Standardized incidence ratios (SIRs)--the ratios of observed-to-expected numbers of cancer--served as measures of relative risk. RESULTS The observed number of noncutaneous cancers occurring in the cohort (n = 115) was close to expected (n = 103.0) (SIR = 1.1; 95% confidence interval, [CI], 0.9-1.3). However, nonmelanoma skin cancer (SIR = 4.3; 95% CI, 3.5-5.4; n = 83), lip cancer (SIR = 8.2; 95% CI, 2.6-19.1; n = 5), and, among men, leukemia (SIR = 3.2; 95% CI, 1.04-7.5; n = 5) occurred in excess. CONCLUSIONS Patients with Bowen disease do not appear to constitutionally be at any unusually high general cancer risk. The increased risk of invasive skin and lip cancers is likely due to the common risk factor of UV light.