Imiquimod

Abstract

Objective: To assess the clinical and histologic effects of topical imiquimod therapy on dysplastic nevi, and to determine the feasibility of using in vivo confocal microscopy (CSLM) to non-invasively monitor histological response of dysplastic nevi to imiquimod therapy.

Design: Single-blinded pilot study with patients not blinded as to treatment status.

Setting: Dermatology Outpatient Clinic, Memorial Sloan-Kettering Cancer Center, New York, NY.

Patients: The study population comprised of 10 patients with clinically dysplastic (atypical) nevi and at least 8 large nevi, ([greater than or equal to]5 mm) on their trunk.

Intervention: Sixteen weeks of imiquimod 5% cream applied to treatment lesions 3 times per week.

Main Outcome Measure: Clinical response as gauged by comparison of baseline and week 20 1:1 standardized photographs for all study nevi and histological assessment of each patient's 4 largest study nevi at completion of therapy.

Results: There were no obvious clinical changes in the size and morphology of the study nevi. Subtle changes in nevus color could not be assessed due to imperfect spectral registration of images over the course of the study. Histologically, 4 of 14 treated nevi and 0 of 14 untreated nevi p=0.03 showed a significant relative reduction of junctional and intraepidermal nevocytes accompanied by papillary dermal fibroses and variable inflammation suggestive of partial regression. Non-invasive CSLM imaging of study nevi demonstrated previously reported in vivo features of dysplastic nevi, but the imaging equipment and protocol utilized proved inconsistent across lesions and time.

Conclusions: The histological changes seen in a subset of treated nevi suggest a possible role for the use of topical immune response modifiers for the treatment of dysplastic nevi with the intent of melanoma chemoprevention. The dose regimen of topical imiquimod utilized in this study failed to induce sufficient clinical or histological responses to warrant further study. Targeting of dysplastic nevi and intermediate endpoints for melanoma chemoprevention with more intense and/or prolonged treatment regimens with imiquimod or the use of other immune response modifiers seems promising. Technical improvements are required for the use of non-invasive CSLM imaging in lieu of invasive histology for the study of topical nevus therapies.

Introduction

In 2005, there will be an estimated 59,580 cases of cutaneous melanoma in the US, with 7,700 deaths. (1) Much of the mortality associated with melanoma could be prevented with effective secondary prevention strategies for early detection of thin lesions that have a much favorable prognosis. To date primary prevention of melanoma has focused on sun protection. (2,3) Dysplastic nevi (DN) are important markers of melanoma risk and potential precursors of a significant subset of melanomas. (4) In patients with dysplastic nevi, approximately 60% of melanomas arise in histologic contiguity with a pre-existing nevus. (3) For patients with many dysplastic nevi, tracking and observation of multiple nevi for clinical and dermoscopic change is expensive and time consuming. (6) Wholesale excision of nevi in these patients is associated with even greater expense and the attendant morbidity of pain and scarring. As clinically, histologically, and molecularly intermediate lesions between banal nevi and superficial spreading melanomas, dysplastic nevi are attractive targets for melanoma chemoprevention.

Imiquimod 5% cream, a topical immunomodulating agent, stimulates immune response through secretion of cytokines, and is thought to activate various antigen presenting cells such as dendritic cells, Langerhans cells, and macrophages. While the effects of imiquimod appear to be mediated in part through activation of the Toll-like receptors 7 and 8, the exact antineoplastic mechanism of action of imiquimod has yet to be elucidated. (7,8) Imiquimod has been approved for the treatment of basal cell carcinomas and actinic keratoses and there are reports of its efficacy for the treatment of superficial basal cell carcinoma, squamous cell carcinoma, melanoma in situ, and cutaneous melanoma metastases. (9-15) We conducted a pilot study to assess the clinical and histologic effects of 5% topical imiquimod on dysplastic nevi. To monitor response to imiquimod, we utilized in vivo confocal microscopy (CSLM), digital photography, and digital dermoscopy, along with serial punch biopsies to evaluate histologic treatment effect.

Methods Patient Population

Patients with multiple clinically dysplastic nevi and a minimum of 8 large (>5 mm) nevi of the trunk were eligible for participation. For the purposes of this study, clinically dysplastic nevi were defined as nevi greater than 5 mm in diameter with a macular component and variable pigmentation or an indistinct "fuzzy" border. All patients were enrolled from the Dermatology Outpatient Clinic at Memorial Sloan-Kettering Cancer Center. The study was approved by the MSKCC Institutional Review Board.

Study Design

It was a single-blinded pilot study with patients not blinded as to treatment status. Imiquimod cream was to be applied 3 times per week to treatment lesions 1 hour prior to bedtime and left on overnight for 6 to 10 hours. Patients were provided annotated clinical overview photographs to help identify treatment lesions. Patients were instructed to wash off treatment cream with mild soap and water the next morning. We chose not to use a vehicle control because we anticipated that application site inflammation from the treatment would preclude patient blinding to a bland placebo and the use of an irritating control might increase the risk of misapplication and confound interpretation of the clinical and histological results. Clinical, dermoscopic, and histologic evaluation of lesions were performed by multiple observers blinded to treatment status.

Treatment Plan

Patients underwent a pretreatment evaluation that included a physical examination and collection of baseline demographic information. The 8 largest nevi of the trunk were identified and assigned study numbers 1 to 8 (largest to smallest). In the event of 2 lesions of identical size the darker of the 2 received the lower number (closer to zero) score. These 8 "study nevi" underwent individual lesion close-up clinical and dermosc opic imaging. The patient was then randomized to the "odd" or "even" treatment group. In the "odd" treatment group lesions 1, 3, 5, and 7 received topical imiquimod treatment and lesions 2, 4, 6, and 8 were observed without therapy. In the "even" group lesions 2, 4, 6, and 8 were treated and lesions 1, 3, 5, and 7 were observed. Imiquimod 5% treatment was initiated at baseline and continued for 16 weeks. The treatment schedule is outlined in Table 1.

Lesion Assessment

All 8 study nevi were evaluated with serial digital photography and dermoscopy at baseline and week 20 for assessment of clinical change. Post therapy imaging was delayed to week 20 to allow resolution of imiquimod induced inflammation. To minimize morbidity, only lesions 1 to 4 underwent histological assessment with non-invasive CSLM imaging at multiple time points and excisional biopsy at study completion (week 20). In addition, the 2 largest nevi for each study participant (lesions 1 and 2) underwent 3 mm punch biopsies at baseline and week 3 for potential use in future correlative molecular studies. Imiquimod treatment for these 2 nevi was held for 3 days following punch biopsy to permit unencumbered healing. Compliance to therapy was monitored with the use of a patient diary and by quantification of residual medication at study completion.

Clinical/Dermoscopic Imaging

One to one close-up clinical and dermoscopic images of all 8 study nevi were obtained at baseline and week 20 using a Fuji S1 digital camera with Canfield ELM attachment (Canfield Scientific Inc., Fairfield, New Jersey). To evaluate the clinical and dermoscopic response, 2 clinicians who specialize in pigmented lesions (AAM, ACH) compared the pairs of clinical photographs obtained from baseline and week 20. Changes in lesion color and size were assessed as having undergone complete response, partial response, no response, or progression. Complete response was defined as reversion to clinically normal skin, partial response was defined as 50% or greater reduction in diameter or significant reduction in pigmentation, no response was defined as no substantial change in size or pigmentation, and progression was defined as an increase in pigment variegation or increase in size of the lesion. Dermoscopic images were assessed for obvious changes in the presence, atypia, and distribution of dermoscopic attributes (eg, pigment network, globules, dots, regression structures).

CSLM Imaging

Confocal imaging was performed with a commercially available, near-infrared, reflectance confocal laser scanning microscope (Vivascope 1000, Lucid Inc, Henrietta, NY). The instrument uses a diode laser at 830 nm with a power of less than 35 mW at tissue level. A 30x water-immersion objective lens of numerical aperture 0.9 was used with either water (refractive index 1.33) or gel (refractive index 1.3335) as an immersion medium. The microscope images with a spatial resolution of 0.5 to 1.0 [micro]m in the lateral dimension and 4 to 5 [micro]m in the axial dimension. An automated stepper was used to obtain a grid of 16 contiguous horizontal images in less than 20 seconds to construct a montage image with an effective in vivo field of view of 1.6 X 2.0 mm. All images obtained by CSLM in this study correspond to sections in the horizontal plane. Subjects underwent CLSM of lesions 1 to 2 at baseline, 3, 8, 17, and 20 weeks. In addition, lesions 3 to 4 were imaged with CLSM at baseline and at week 20.

Histological Evaluation

Skin biopsies and excisions were fixed in formalin and embedded in paraffin according to standard procedures. At least 3 step sections of each tissue section were obtained. The cases of this study were reviewed by 2 dermatopathologists (KJB, RD). Published criteria for the diagnosis and grading of dysplastic nevi were used. (16-18).

Results

A total of 10 subjects (6 males and 4 females) were enrolled. Of those enrolled, 7 completed the 20-week treatment protocol. All subjects had clinically floridly expressed dysplastic nevi with 8 or more trunk nevi meeting our clinical definition of dysplastic nevi. One patient was hospitalized for severe abdominal pain shortly after start of treatment and was diagnosed with appendicitis. This patient was discontinued from the study due to noncompliance during the course and the resolution of this non-treatment related adverse event. Two other patients were non-compliant with the study protocol and were removed from the study at 8 and 17 weeks, respectively. Seven patients completed all of the protocol requirements and were analyzed.

Clinical/Dermoscopic Findings

All patients reported mild to moderate treatment site irritation, but no instance of irritation resulted in treatment interruption. Mild erythema was observed in treatment nevi during therapy without any instances of ulceration or clinical signs of severe inflammation or infection. Comparison of baseline and week 20 clinical and dermoscopic images revealed stability of all study nevi without any evidence of significant change in size, pigment variegation, or dermoscopic features with the exception of focal changes at the punch biopsy sites in lesions 1 and 2. Overall color comparison was confounded by a switch in the flash element during the course of the study, precluding assessment of changes in the background color of lesions over time. Focal dermoscopic changes were noted at 2 of the punch biopsy sites. The first type of change was the development of a pink, scar-like area with overlying thin blood vessels. The second focal dermoscopic change consisted of the development of blue-grey to black pigmentation at and around the biopsy site (Figure 1). This type of pigmentation is reminiscent of regression structures and probably represents dermal melanin within melanophages.

Histological Findings

Thirteen out of 14 treated and 11 out of 14 untreated lesions met histologic criteria for dysplastic melanocytic nevi (Table 2). The majority of the nevi were of the compound type. The degree of melanocytic atypia ranged from slight to moderate. Of the nevi (7 treated and 7 untreated) that underwent punch biopsy prior to excision, no significant histologic changes were noted between biopsy at baseline and at 3 weeks, and the biopsy diagnoses were largely representative of the final excisional diagnoses. On excisional specimens, in addition to dermal scar, 2 out of the 14 nevi previously biopsied (in 2 of the 7 patients), showed focal histologic evidence of a recurrent/persistent nevus phenomenon (so-called "pseudomelanoma").

Upon completion of the study, 4 treated nevi (from 3 patients) showed significant reduction in the number of junctional and intraepidermal melanocytes, accompanied by papillary dermal fibrosis and variable inflammation.

CSLM Findings

CSLM images of lesions 1 and 2 from baseline, 3, 8, 17, and 20 weeks and of lesions 3 and 4 from baseline and week 20 were reviewed. CSLM images showed variation in size, shape, and location of junctional nests, as well as features of an altered epidermal architecture, consistent with what has previously been reported for dysplastic nevi. CSLM image quality was found to vary among lesions and over time. Further assessments determined the image variability to relate to both inconsistencies in the performance of the instrument and to inadequate adherence to a rigorous protocol for image acquisition.

[FIGURE 1 OMITTED]

[FIGURE 2 OMITTED]

Discussion

Current strategies for the primary prevention of melanoma are predicated on sun protection. While this approach is supported by strong epidemiologic and basic science evidence of a role for ultraviolet exposure in the pathogenesis of most melanomas, it lacks direct evidence of efficacy, flies in the face of current aesthetic and cultural norms, and may take decades to have an effect assuming a significant lag period between exposure and disease. As a result, novel approaches to melanoma chemoprevention deserve investigation. In the absence of established biomarkers for the intermediate steps of melanocytic tumor progression, dysplastic nevi are attractive targets for studies of melanoma chemoprevention. While the overwhelming majority of dysplastic nevi are not destined to progress to melanoma and the majority of melanomas do not arise in dysplastic nevi, these lesions are nonetheless strong markers of melanoma risk and potential precursors of the disease that manifest clinical, histologic, and immunohistologic features that are intermediate between common nevi and melanoma. A chemoprevention strategy that "normalizes" or eliminates dysplastic nevi would hold significant promise for preventing melanoma and great public health significance for these patients who are currently managed with close surveillance and preemptive excision of changed and concerning lesions. Recent preliminary reports of the efficacy of topical imiquimod in the treatment of lentigo maligna and some cutaneous melanoma metastases speak to the potential use of immune response modifiers (IRMs) for the chemoprevention of melanoma. Here, we undertook a pilot study to assess the effect of topical imiquimod on dysplastic nevi.

While the clinical responses in this very small study were underwhelming, the evidence for a histologic response in a subset of treated nevi suggests a possible role for topical IRMs in melanoma chemoprevention. Four of our 14 excised treated nevi showed inflammatory and fibrosing changes suggestive of partial regression. Because only 1 of the 4 nevi had been previously biopsied, it is unlikely that the inflammation observed in those cases was related to prior surgical procedure. Moreover, it is of interest that a pseudomelanoma-phenomenon, identified in 2 patients (# 5 and #6 in Table 2), developed only in untreated nevi. The latter findings support the hypothesis that imiquimod may (directly or indirectly) affect the proliferation of melanocytes.

[FIGURE 3 OMITTED]

Our selection of a 3 times per week dosing schedule and 16-week treatment period may have been unfortunate in light of recently published and anecdotal reports of imiquimod treatment of lentigo maligna in which a daily dosing schedule appears to be well-tolerated and prolonged treatment often necessary. (11,19) Additional studies of the effect of more intense and prolonged topical therapy of dysplastic nevi with imiquimod are warranted unless new IRMs or differentiating agents with greater selectivity for melanocytes are forthcoming. In the event of demonstrated clinical/histologic efficacy, correlative studies to assess the mechanisms of action will be critical to the development of increasingly selective agents and the design of public health strategies. As in all chemoprevention strategies, an excellent safety profile, prolonged effect, cost-effectiveness, and so forth would all have to be addressed prior to acceptance in clinical practice.

A secondary aim of this pilot study was to assess the feasibility of using CSLM to non-invasively monitor histologic response of nevi to topical imiquimod therapy. In the case of basal cell carcinoma, clinical assessment of response to imiquimod therapy can underestimate histologic response. (20) Although the confocal images obtained in this study proved inadequate to assess the limited changes observed on ex vivo histology, they confirmed the ability of non-invasive imaging to document the presence of nevic nests and architectural disorder. Newer generation instruments permit standardized acquisition of grids of confocal images registered to macroscopic real time images of the lesion. If this advance can be coupled with more consistent instrument performance across lesions over time, non-invasive CSLM imaging could serve as a primary endpoint for demonstration of clearance of nevic nests and normalization of epidermal and dermal papillae architecture.

Disclosure

This study was supported by an investigator initiated unrestricted grant from 3M pharmaceuticals.

References

1. American Cancer Society. Cancer Facts and Figures. Available at: http://www.cancer.org/downloads/STT/CAFF2005f4PWSecured.pdf. Last accessed November 11, 2005.

2. Huncharek M, Kupelnick B. Use of topical sunscreens and the risk of malignant melanoma: a meta-analysis of 9067 patients from 11 case-control studies. Am J Public Health. 2002;92:1173-7.

3. Dennis LK, Beane Freeman LE, VanBeek MJ. Sunscreen use and the risk for melanoma: a quantitative review. Annals of Internal Medicine. 2003;139(12):966-78.

4. Bevona C, Goggins W, Quinn T, Fullerton J, Tsao H. Cutaneous melanomas associated with nevi. Arch Dermatol. 2003;139(12):1620-4.

5. Tucker MA, Fraser MC, Goldstein AM, et al. A natural history of melanomas and dysplastic nevi: an atlas of lesions in melanomaprone families. Cancer. 2002;94(12):3192-209.

6. Kelly JW, Yeatman JM, Regalia C, Mason G, Henham AP. A high incidence of melanoma found in patients with multiple dysplastic naevi by photographic surveillance. Med J Aust. 1997;167(4):191-4.

7. Ambach A, Bonnekoh B, Nguyen M, Schon MP, Gollnick H. Imiquimod, a Toll-like receptor-7 agonist, induces perforin in cytotoxic T lymphocytes in vitro. Mol Immunol. 2004;40(18):1307-14.

8. Martin-Garcia RF. New insights into imiquimod's mechanisms of action. J Drugs Dermatol. 2004;3(3):247-9.

9. Bong AB, Bonnekoh B, Franke I, Schon MP, Ulrich J, Gollnick H. Imiquimod, a topical immune response modifier, in the treatment of cutaneous metastases of malignant melanoma. Dermatology. 2002;205(2):135-8.

10. Chapman MS, Spencer SK, Brennick JB. Histologic resolution of melanoma in situ (lentigo maligna) with 5% imiquimod cream. Arch Dermatol. 2003;139(7):943-4.

11. Geisse J, Caro I, Lindholm J, Golitz L, Stampone P, Owens M. Imiquimod 5% cream for the treatment of superficial basal cell carcinoma: results from two phase III, randomized, vehicle-controlled studies. J Am Acad Dermatol. 2004;50(5):722-33.

12. Fisher GH, Lang PG. Treatment of melanoma in situ on sun-damaged skin with topical 5% imiquimod cream complicated by the development of invasive disease. Arch Dermatology. 2003;139(7):945-7.

13. Shumack S, Gebauer K, Quirk C, Macdonald K, Walters SA, Owens M. 5% imiquimod cream for the treatment of large superficial basal cell carcinoma. Arch Dermatol. 2004;140(10):1286-7.

14. Szeimies RM, Gerritsen MJ, Gupta G, et al. Imiquimod 5% cream for the treatment of actinic keratosis: results from a phase III, randomized, double-blind, vehicle-controlled, clinical trial with histology. J Am Acad Dermatol. 2004;51(4):547-55.

15. Smith KJ, Hamza S, Skelton H. Topical imidazoquinoline therapy of cutaneous squamous cell carcinoma polarizes lymphoid and monocyte/macrophage populations to a Th1 and M1 cytokine pattern. Clin Exp Dermatol. 2004;29(5):505-12.

16. Arumi-Uria M, McNutt NS, Finnerty B. Grading of atypia in nevi: correlation with melanoma risk. Mod Pathol. 2003;16(8):764-71.

17. Crowson AN, Magro CM, Mihm MC. The Melanocytic Proliferations: A Comprehensive Textbook of Pigmented Lesions. New York: John Wiley & Sons, 2001.

18. Elder DE, Murphy GF. Melanocytic tumors of the skin. In: Rosai J, Sobhin LH, eds. Atlas of Tumor Pathology. Washington, DC: Armed Forces Institute of Pathology, 1991.

19. Fleming CJ, Bryden AM, Evans A, Dawe RS, Ibbotson SH. A pilot study of treatment of lentigo maligna with 5% imiquimod cream. Br J Dermatol. 2004;151(12):485-8.

20. Nori S, Rius-Diaz F, Cuevas J, et al. Sensitivity and specificity of reflectance-mode confocal microscopy for in vivo diagnosis of basal cell carcinoma: a multicenter study. J Am Acad Dermatol. 2004;51(6):923-30.

Address for Correspondence

Stephen W. Dusza

Memorial Sloan-Kettering Cancer Center

160 East 53rd St.

New York, NY 10022

e-mail: duszas@mskcc.org

Stephen W. Dusza MPH, (a) Ruby Delgado MD, (b) Klaus J. Busam MD, (b) Ashfaq A. Marghoob MD, (a) Allan C. Halpern MD (a)

a. Dermatology Service, Department of Medicine, Memorial Sloan-Kettering Cancer Center, New York, NY

b. Department of Pathology, Memorial Sloan-Kettering Cancer Center, New York, NY

COPYRIGHT 2006 Journal of Drugs in Dermatology, Inc.
COPYRIGHT 2006 Gale Group