Recurrence rates of treated basal cell carcinomas. Part 1: Overview.

This is the first article in a series reviewing the extensive experience of the Oncology Section of the Skin and Cancer Unit, from 1955 through 1982, with 5755 basal cell carcinomas (BCCs) treated by curettage-electrodesiccation, surgical excision, or x-ray therapy. Recurrence rates were calculated by three methods for each of the treatment modalities: 1) by the raw recurrence rate method; 2) by the "strict" 5-year recurrence rate method; and 3) by modification of the life-table method. Our analyses show that the last method best approximates the true recurrence rate. Primary (previously untreated) BCCs had a 5-year recurrence rate of 10.6% (standard error 0.6%), and previously treated BCCs had a rate of 15.4% (standard error 1.3%) (P = .0002). The greatest risk for recurrence of treated primary BCCs occurred 1 to 4 years after therapy. It is concluded that recurrence rates of primary BCCs should be reported separately from those of previously treated BCCs and that the modified life-table method is best suited to calculate 5-year recurrence rates.