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More clinical trials will better define imiquimod’s role in lentigo maligna
NEW YORK — Topical imiquimod can be beneficial in the treatment of lentigo maligna, but questions remain regarding its efficacy, according to a review of clinical trials.
Imiquimod was first developed as a cream for use on genital warts.
“The antitumor effects were quickly observed, and intraepithelial neoplasia became the focus,” said Scott W. Fosko, MD, chairman of the department of dermatology and director of the division of Mohs’ micrographic surgery and cutaneous oncology at Saint Louis University School of Medicine.
Imiquimod has since been approved for actinic keratoses and superficial basal cell carcinomas, although it is not FDA approved for lentigo maligna, an in situ subtype of lentigo maligna melanoma that often arises in sun-damaged skin.
“Does imiquimod work for lentigo maligna?” Fosko said. “The literature says ‘yes,’ but neither reliably nor predictably.”
In a study by Ly and colleagues, published in 2011 in the Archives of Dermatology, researchers found imiquimod cream had limited efficacy in the treatment of lentigo maligna when determined by histopathologic assessment of the entire treated area.
Researchers also concluded that clinical signs of visible inflammation during treatment and apparent lesion clearance could not be relied upon to assess efficacy.
“In this study, when you look at patients who were clear clinically, 35% exhibited disease histologically,” Fosko said. “Likewise, in patients who appeared to have disease, 39% were clear histologically, so clinical features do not necessarily predict ultimate outcome.”
A study by Hyde and colleagues, published online in the Archives of Dermatology earlier this year, evaluated treatment with topical imiquimod plus tazarotene (Avage, Tazorac; Allergan), with topical imiquimod alone.
Patients in the imiquimod/tazarotene group exhibited 22% of lesions with residual lentigo maligna on staged excisions vs. 36% of patients treated with imiquimod alone, according to study results. The researchers theorized that pretreating lentigo maligna with imiquimod may decrease surgical defect sizes, yet complete reliance on imiquimod as a surgical alternative could put the patient at increased risk of a local recurrence.
“We are relatively early in our imiquimod use, with the first case only being reported in 2000 and the first case series in 2003,” Fosko said. “We’re early in understanding its role [and] understanding and identifying ideal treatment regimens, and we have much more to learn with regard to patient selection and the influence of genetic and tumor factors.”
A study by Cotter and colleagues, published in 2008 in Dermatologic Surgery, reviewed the clinical response of patients treated with imiquimod before staged excision. After a mean follow-up of 18 months and complete surgical excision of the treatment site, none of the imiquimod-treated patients exhibited evidence of recurrence. The researchers concluded that although imiquimod appeared to be an effective adjunctive treatment for lentigo maligna, it would not qualify as a replacement therapy for surgery.
“What is the future role of imiquimod in lentigo maligna?” Fosko said. “We can improve outcomes for select patients either as monotherapy or neoadjuvant or adjuvant [therapy] by treating both the obvious clinical and histopathologic disease, as well as the subclinical and subhistopathologic disease. There is much more to learn, and we’re continuing to evaluate this in our clinical trials.”
- Cotter MA. Dermatol Surg. 2008;34:147-151.
- Hyde MA. Arch Dermatol. 2012;doi:10.1001/archdermatol.2012.270.
- Ly L. Arch Dermatol. 2011;147:1191-1195.
Disclosure: Dr. Fosko reports no relevant financial disclosures.