RECURRENCE RATES OF TREATED BASAL-CELL CARCINOMAS .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 a 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 occured 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 lifetable method is best suited to calculate 5-year recurrence rates.