Development of Vitiligo-Like Depigmentation after Treatment of Lentigo Maligna Melanoma with 5% Imiquimod Cream

Topical Treatment of Melanoma In Situ, Lentigo Maligna, and Lentigo Maligna Melanoma with Imiquimod Cream: A Systematic Review of the Literature

INTRODUCTION

The classical management of melanoma is surgery, but this can be challenging because of several factors, such as age, body area, lesion size, among others. Topical imiquimod may be a therapeutic option for the treatment of melanoma in situ and lentigo maligna melanoma due to its efficacy, tolerability, and non-invasiveness. The purpose of this systematic review is to assemble current evidence on the treatment of non-metastatic melanoma with topical imiquimod.

METHODS

The PubMed/MEDLINE and Cochrane Library databases were searched as the primary sources using the main search terms "imiquimod" combined with "lentigo maligna" and "melanoma" with the command "AND." Articles were identified, screened, and extracted for relevant data, following the PRISMA guidelines.

RESULTS

A total of 87 studies covering 1803 lesions treated with imiquimod cream were identified and included in this sytematic review. Forty-nine studies were case reports, 16 were retrospective analyses, 3 were open label trials, six were case series; one study was a controlled randomized trial, one was a randomized trial, and one was a single-arm phase III trial. Because of the high number of low-evidence studies, the overall risk of bias resulted high. In 55 studies, imiquimod 5% was used in monotherapy as the primary treatment; only in one study was imiquimod 3.75% introduced. In most cases, the topical treatment was applied once daily, with the exception of nine cases where an increased daily dosage was prescribed. The total duration of the treatment regimen was extremely variable and depended on body area and tolerability, with differences among patients of the same study. In six studies, imiquimod was used as neoadjuvant therapy before the surgical excision, and in 11 studies it was used after surgery as complementary or adjuvant therapy. In total, 1133 of the 1803 (62.8%) lesions were reported to be cleared after the treatment, taking into account that not all of the patients completed the treatment. Of these 1133 lesions, histological clearance was achieved in 645 (56.9%) lesions and clinical clearance only was achieved in 490 (43.2%) lesions; relapse occurred in 107 lesions.

CONCLUSIONS

The heterogeneity of the studies included in this systematic review precludes the drawing of any relevant conclusions regarding the application of imiquimod. Its efficacy in melanoma in situ and lentigo maligna melanoma has been demonstrated, but further evidence from controlled studies concerning the modalities is missing.

Topical and Intralesional Immunotherapy for Melanoma In Situ: A Review

The incidence of in situ melanoma (MIS) has increased over the last decades. The mainstay of treatment for MIS, including lentigo maligna (LM), is complete surgical excision with clear margins (0.5 to 1.0 cm). Nevertheless, MIS lesions often affect elderly patients with comorbidities and involve large lesions in cosmetically sensitive areas, which means surgery is not always appropriate. Non-surgical treatments have a role in these cases, and include radiotherapy, cryosurgery, immunotherapy, laser therapy, and other topical medications. This study aims to review the applications of immunotherapy in MIS, either in monotherapy or in combination with other therapeutic alternatives. The main forms of immunotherapy used are imiquimod and, to a lesser extent, intralesional interferon-α (IL-INF-α) and ingenol mebutate (IM). IL-INF-α and IM have not been studied as extensively as imiquimod, whose results in real-life practice are encouraging. The clearance and recurrence rates reported in MIS treated with imiquimod as monotherapy, or as an adjuvant after surgery with affected or narrow margins, make imiquimod a reliable therapeutic alternative in selected cases. Also, its use as a neoadjuvant therapy before surgery was shown to reduce the final surgical defect size required to confirm negative histologic margins. In conclusion, local immunotherapy is frequently used in clinical practice and experience confirms it to be an excellent option for certain patients.

Rare Cutaneous Side Effects of Imiquimod: A Review on Its Mechanisms, Diagnosis, and Management

As an immune-response modifier, imiquimod can bind to Toll-like receptors on immune cells and enhance innate and adaptive immune responses, exerting potential antitumor and antiviral effects, which led to its approval by the US Food and Drug Administration for the treatment of actinic keratosis, superficial basal cell carcinomas, and anogenital warts, and to its off-label use in treating many other benign and malignant dermatoses. Although topical administration of imiquimod has been considered well tolerated, an increasing number of cutaneous and noncutaneous side effects are being reported as its clinical applications expand. This review primarily focuses on rare cutaneous side effects. To the best of our knowledge, this is the first article to summarize the mechanism, diagnosis, and management of rare cutaneous side effects of imiquimod, which may help to heighten awareness among physicians, especially dermatologists, about potential imiquimod-induced cutaneous side effects.

Imiquimod induced vitiligo-like lesions-A consequence of modified melanocyte function

INTRODUCTION

Imiquimod plays an important role in the management of condyloma and premalignant lesions. Successively, an increase of hypopigmented lesions following imiquimod application has been reported. However, the mechanisms of imiquimod on melanocytes remain unclear. This study was designed to assess the effect of Imiquimod on the functions of melanocytes in vitro.

METHODS

Primary cultured melanocytes were isolated from normal control skin tissue. After incubation with imiquimod for 48 h in vitro, cell viability was analyzed by cell counting kit-8 assay. Apoptosis was detected using the Annexin V-fluorescein-5-isothiocyanate flow cytometry assay. Melanin content and tyrosinase activity in melanocytes were measured by colorimetric method and the modified dopachrome method. The production of inflammatory cytokine interleukin 8 (IL-8), IL-6, and soluble ICAM-1 (soluble Intercellular Adhesion Molecule-1[sICAM-1]) in melanocytes were measured by enzyme-linked immunosorbent assay (ELISA). Toll-like receptor 7 (TLR7), toll-like receptor 9 (TLR9) protein, and autophagy-related proteins microtubule-associated protein 1A/1B-light chain 3 (LC3-II), p62, mechanistic target of rapamycin (mTOR), and Atg5 were assessed using western blot analysis.

RESULTS

Imiquimod significantly inhibited the activity of tyrosinase activity and decreased melanin content in melanocytes and significantly increased apoptosis and IL-6, IL-8, and sICAM-1 production in melanocytes. Moreover, the expression of TLR7 and TLR9 proteins were significantly increased, and the expression of mTOR, p62 protein were markedly decreased, but the expression of LC3II/I and Atg5 protein were significantly increased in melanocytes after incubating with imiquimod.

CONCLUSIONS

This study shows that imiquimod directly inhibits melanogenesis and increases melanocyte apoptosis rates. These effects combined with the upregulation of TLR7 and TLR9 together with increased autophagy activity and inflammatory cytokines production, might be the main reasons leading to hypopigmented lesions after imiquimod application.

Drug-induced vitiligo: a case/non-case study in Vigibase® , the WHO pharmacovigilance database

Vitiligo is a common depigmenting disorder ensuing the loss of epidermal melanocytes. It is a multifactorial disease with immunological, genetic and environmental factors including drug exposure. The purpose of the study was to investigate the drugs and therapeutic subclasses associated with vitiligo occurrence reported in VigiBase^® , the WHO pharmacovigilance database. A case/non-case study was carried out by defining cases as vitiligo reports and non-cases as all other reports. The reporting odds ratio (ROR) was calculated for the 'suspected' drugs and drug classes according to ATC level 4. During the study period, 741 cases of vitiligo were registered. Mean age was 49 ± 20 years. The disproportionality analysis showed an association between vitiligo and pembrolizumab (ROR 116.9, 95% Confidence Interval (CI) 94.8, 144.3), nivolumab (ROR 22.6, 95% CI 15.8, 32.4), ipilimumab (ROR 41.7, 95% CI 25.0, 69.7), imiquimod (ROR 152.8, 95% CI 103.0, 226.7), adalimumab (ROR 3.8, 95% CI 2.5,5.8), infliximab (ROR 2.6, 95% CI 1.65, 4.01), alemtuzumab (ROR 27.8, 95% CI 17.6, 43.9), and ustekinumab (ROR 9.3, 95% CI 5.6, 15.6). Concerning the pharmacological classes ATC level 4, a significant association was found with monoclonal antibodies, interferons, selective immunosuppressants, TNF-alpha inhibitors, interleukin inhibitors, and topical antivirals. This study confirmed the expected associations between vitiligo and immune checkpoint inhibitors and strengthened the emerging signal about the association between vitiligo and imiquimod, TNF-alpha inhibitors and interferons. New signals were shown with selective immunosuppressants including alemtuzumab and interleukin inhibitors.

The Role of Toll-Like Receptors in Oncotherapy

Toll-like receptors (TLRs) are associated with tumor growth and immunosuppression, as well as apoptosis and immune system activation. TLRs can activate apoptosis and innate and adaptive immunity pathways, which can be pharmacologically targeted for the development of anticancer oncotherapies. Several studies and clinical trials indicate that TLR agonists are promising adjuvants or elements of novel therapies, particularly when used in conjunction with chemotherapy or radiotherapy. An increasing number of studies suggest that the activation of TLRs in various cancer types is related to oncotherapy; however, before this finding can be applied to clinical practice, additional studies are required. Research suggests that TLR agonists may have potential applications in cancer therapy; nevertheless, because TLR signaling can also promote tumorigenesis, a critical and comprehensive evaluation of TLR action is warranted. This review focuses on recent studies that have assessed the strengths and weaknesses of utilizing TLR agonists as potential anticancer agents.