The present study was planned to evaluate the efficacy and tolerability of topical treatment with imiquimod in nodular basal cell carcinoma (nBCC).

One hundred two patients were randomized to receive thrice-weekly topical imiquimod for either 8 or 12 weeks. Twelve patients dropped out. A total of 90 patients were evaluated for tolerability and efficacy. Histologic clearance was controlled by excising the original tumor location with 3-mm margins and evaluating with permanent sections the cut-surgical margin, including the deep margin, and with serial step-sectioning the central portion of the tissue for tumor persistence.

There were no significant differences between the treatment arms with respect to efficacy and tolerability. Of 90 evaluable patients, 70 had a complete clinical clearance (78%). Clinically visible tumor was still present in 20 patients (22%). A complete histopathological clearance was observed in 58 patients (64%). Tumor persisted in 32 patients (36%). In 12 patients, despite complete clinical clearance, tumor remnants were still detected in histopathological evaluation. Efficacy was better in nBCC that was less than 1 cm in diameter, showing 82% clinical and 72% histopathologic clearing. Adverse events were reported in 92% of the patients and were mainly classified as minor or moderate local inflammation.

Clinical follow-up was limited to the time period between end of treatment and final complete excision.

Imiquimod applied thrice weekly for 8 and 12 weeks shows modest activity against small nBCC. Residual tumor was present in more than one third of treated patients. Clinical appearance after treatment does not accurately reflect the presence or absence of disease in nearly 1 of every 5 patients with nBCC. Since 17% of patients with clinical clearance still have pathologic evidence of disease, excisional biopsy of the treated site is still indicated.