Clinical and Immunologic Results of a Phase II Trial of Sequential Imiquimod and Photodynamic Therapy for Vulval Intraepithelial Neoplasia

Purpose: High-risk human papillomavirus (HPV)-associated vulval intraepithelial neoplasia (VIN) is difficult to treat by excision or ablation because of high recurrence rates. Small studies of photodynamic therapy (PDT) and imiquimod treatments have shown some success and function at least in part through stimulation of local immune responses. Indeed, there is evidence that immunosuppressed individuals have higher rates of VIN, suggesting immune control is relevant. Experimental Design: In the study, 20 women with high-grade VIN were treated with topical imiquimod and the PDT sequentially. Vulval biopsy and blood were taken pretreatment and, after imiquimod and PDT, with follow up for 1 year. Clinical response was assessed by measuring lesion size. Biopsies were analyzed for HPV DNA and tumor-infiltrating lymphocytes including T regulatory cells. Results: The treatment was well-tolerated. There was an overall response rate of 55% by intention treat and 64% per protocol. The 52-week symptom response was 65% asymptomatic, compared with 5% at baseline. The nonresponders showed a significantly higher level of T regulatory cells in the lesions after imiquimod treatment. Conclusions: The response rates are clinically relevant, and the treatment regimen was feasible for the majority. Initial nonresponders to imiquimod seem to be relatively refractory, and this may derive from their unfavorable local immune environment, in particular, the increased proportions of T regulatory cells, possibly the limiting action and/or development of any HPV T-cell immunity. The potential benefit of this treatment is its ability to treat multifocal disease.