Cancerization field; Risk; Cutaneous neoplasm; Second primary.

Background: Patients with basal cell carcinoma (BCC) have an increased risk of subsequent BCCs. It is possible that imiquimod might reduce this risk by acting on the cancerization field. Objective: To examine the ability of imiquimod to reduce subsequent BCCs. Methods: Retrospective cohort study of patients with BCC treated at our hospital between 2003 and 2011. The patients were divided into 2 groups depending on whether they had been treated with surgery or with imiquimod. Comparing the 2 groups, we analyzed the development of new BCCs, the time that elapsed between first and subsequent tumors, and the site of occurrence of the second BCC with respect to the first one (local, same lymphatic drainage basin or anatomic region, or other). Survival methods were used to analyze the data. Results: We reviewed the charts of 623 patients. Of these, 550 had been treated with surgery (88.3%) and 71 with imiquimod (11.4%). Overall, a second BCC occurred in 36.4 % of patients (n = 227). The rate of occurrence was 38.2 % in the surgery group and 23.9 % in the imiquimod group (P = .02). The hazard ratio for the occurrence of a subsequent BCC was 2.13 (95 % CI, 1.28-3.53) for patients treated with surgery compared with those treated with imiquimod. Imiquimo