Objective: To address the subsequent risk of internal cancer in a population-based cohort of patients with Bowen's disease.
Design: Incident cases of skin cancers other than malignant melanoma occurring in a defined population were classified as basal cell carcinoma, squamous cell carcinoma, or Bowen's disease. Through medical records, all patients were followed up for the development of subsequent internal cancer until they died, moved from Rochester, Minn, or January 1, 1986, whichever came first. Incidence rates of skin cancer and subsequent cancer were computed; the subsequent rate of internal cancer was compared with that prevailing in the community.
Patients: Enrolled were all permanent residents in the population base of Rochester, Minn, who developed basal cell carcinoma (n = 657), squamous cell carcinoma (n = 169), or Bowen's disease (n = 71) on the basis of pathologic examination and clinical presentation from 1976 through 1984.
Main outcome measure: The relative risk of subsequent internal cancer among patients with Bowen's disease compared with that of the population base from which they arose was 1.1 (95% confidence limits, 0.5, 1.6).
Results: Annual incidence rates, adjusted to the 1980 US white population, were 14.9 per 100,000 for Bowen's disease, 38.8 for squamous cell carcinoma, and 146 for basal cell carcinoma. The estimated relative risk for subsequent cancer was 0.9 (95% confidence limits, 0.5, 1.6) among patients with squamous cell carcinoma and 1.0 (95% confidence limits, 0.7, 1.3) for patients with basal cell carcinoma. These risks were not significantly different for various durations of follow-up or for sun-exposed vs sun-protected sites.
Conclusions: We find no evidence in these population-based cohort data of and increased risk of subsequent internal cancer associated with Bowen's disease or other forms of nonmelanomatous skin cancer.