The aim of this retrospective survey was to determine recurrence rates after treatment of basal cell carcinomas in a single academic dermatology department. A total of 1016 patients with 1593 histologically verified basal cell carcinomas (n=1212 primary and n=381 relapsing) were included. Tumour localization, T-stage and the method of treatment were significant predictors of the risk of recurrence (forward Cox regression, p <0.001). The relapse rate for primary basal cell carcinomas on the scalp was highest (odds ratio (OR)=2.8, 95% confidence interval (CI) 1.5-5.3). T2 and T3 tumours showed a 2- and 3-fold increased relapse rate, respectively, compared with T1 basal cell carcinomas. Radiotherapy and surgical excision had the lowest relapse rates, whereas curettage and photodynamic therapy resulted in 5-year relapse rates of up to 70%. Patients with chronic skin diseases had a 50% lower risk of relapse than healthy patients (OR=0.5, CI=0.3-0.8). Recurrent basal cell carcinomas had a higher relapse rate than primary lesions (OR=1.8, CI=1.4-2.2). Patients treated in a specialized skin cancer unit had a 6.4-fold (CI=2.4-17.4) higher cure rate compared with those treated by less experienced physicians. Thus, in an uncontrolled, real-life situation curettage or photodynamic therapy are associated with significantly higher relapse risk than excision and radiotherapy and therefore should not be used for high risk primary tumours or recurrent tumours. Treatment in the setting of a specialized skin cancer unit yields a much lower relapse rate.
