Background: Large-diameter lesions of Bowen's disease at sites such as the shin may be difficult to treat surgically and may require alternate treatment modalities.
Objective: We investigated whether imiquimod 5% cream, a topical immune response modifier that stimulates the production of interferon alfa and other cytokines, is an effective topical treatment for Bowen's disease.
Methods: This was a phase II, open-label study in 16 patients, treating a single biopsy-proven plaque of Bowen's disease that was 1 cm or larger in diameter, with once-daily self-application of imiquimod 5% cream for 16 weeks. A biopsy was performed on the treated area 6 weeks after the end of treatment, with patient follow-up at 3 and 6 months. Lymphocyte CD4/CD8 ratios were analyzed in pretreatment and posttreatment biopsy specimens by immunophenotyping the lymphocytic infiltrate.
Results: Sixteen patients with Bowen's disease lesions ranging from 1 to 5.4 cm in diameter (0.7-21.6 cm(2) in area) were treated. Fifteen of these lesions were on the legs, and one was on the shoulder. Fourteen of the 15 patients (93% per protocol analysis) had no residual tumor present in their 6-week posttreatment biopsy specimens. One patient died of unrelated intercurrent illness before a biopsy specimen could be obtained. The median CD4/CD8 lymphocyte ratio in pretreatment biopsy specimens was 2:1, and this was reversed to a median of 1:2.2 in the posttreatment specimens. Ten patients completed 16 weeks of treatment, but 6 patients ceased treatment early (between 4 and 8 weeks) because of local skin reactions.
Conclusion: Imiquimod 5% cream appears to be an effective treatment for Bowen's disease on the lower limbs. The 93% positive treatment response in biopsy-proven cases (excludes patient who died from an intercurrent illness who did not undergo a posttreatment biopsy) compares favorably with other current treatment modalities. The dosing schedule and length of treatment for Bowen's disease require further evaluation.