Objective: To establish a safe and efficacious dosing regimen for the treatment of primary nodular basal cell carcinoma (BCC) using 5% imiquimod cream. Design: Two phase 2 studies were conducted: a 6-week, randomized, open-label, dose-response study evaluating 4 dosing regimens and a 12-week, randomized, vehicle-controlled, double-blind, dose-response study evaluating 4 dosing regimens. Setting: Twenty-four public and private dermatology clinics in Australia and New Zealand (6-week study) and the United States (12-week study) participated. Patients: The study populations comprised 99 patients enrolled in the 6-week study and 92 patients in the 12-week study. Patients were at least 18 years old and had a biopsy-confirmed diagnosis of nodular BCC. Interventions: In the 6-week study, imiquimod was applied once daily for 3 or 7 days per week or twice daily for 3 or 7 days per week. In the 12-week study, imiquimod or placebo cream (vehicle) was applied once daily for 3, 5, or 7 days per week, or twice daily for 7 days per week. The entire tumor area was excised 6 weeks after treatment and examined histologically for evidence of remaining BCC. Main Outcome Measure: The proportion of patients having no histologic evidence of BCC in the posttreatment excision specimen. Results: Dosing once daily for 7 days per week resulted in the highest clearance rate, with 25 (71%) of 35 and 16 (76%) of 21 patients showing clearance of their tumor in the 6- and 12-week studies, respectively. Conclusions: Topical 5% imiquimod cream is well tolerated and most effective in treating nodular BCC when applied once daily for 7 days per week for either 12 or 6 weeks.
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