Penile intraepithelial neoplasia incidence, clinical classification, microenvironment and implications for imiquimod treatment

Objectives

To provide an outline of the existing data on penile intraepithelial neoplasia (PeIN), as well as a narrative review on imiquimod (IQ; a toll-like receptor 7 agonist) treatment and immune microenvironment markers that may predict response to treatment.

Methods

A narrative review of the literature from 2000 to the present was conducted on PubMed, and we describe the most relevant data and cross references.

Results

The incidence of PeIN is increasing. Local therapy with IQ may offer an easy applicable treatment with complete response rates of up to 63% but can be associated with considerable side-effects. There is no conclusive data on the optimal treatment schedule for PeIN, but evaluation of treatment results for other human papillomavirus-related pre-malignancies suggest three times a week for a duration up to 16 weeks. There are no published studies concerning the PeIN immune microenvironment. However, findings from the few studies on penile cancer and pre-cancerous vulvar and cervical lesions imply that specific immune cell subpopulations can serve as future predictors for successful immunomodulation treatments such as IQ.

Conclusions

Overall, limited data are available on IQ treatment for PeIN and no published data exists on the PeIN immune microenvironment. Further translational studies are warranted to gain more understanding on the pathophysiology of PeIN and potential predictors of progression and of response to topical treatments.