Imiquimod may be best treatment for lentigo maligna

January 1, 2006

Las Vegas — Accumulating research indicates that topical imiquimod (5 percent) is efficacious for the treatment of lentigo maligna, Shane M. Chapman, M.D., an assistant professor at Dartmouth Medical School in Hanover, NH, says.

"Right now surgical excision remains the standard of care," he says. "But based on a growing body of case studies, there's evidence that imiquimod may be considered in certain circumstances."

Dr. Chapman cites three such circumstances:

Dr. Chapman began investigating nonsurgical options for lentigo maligna almost four years ago. At the time, there was just a single case report, suggesting that imiquimod might work. It was met by a lot of professional skepticism.

"My research has been driven by patients who needed another alternative," he tells Dermatology Times. "I wanted to confirm whether or not imiquimod worked."

He began treating the occasional patient in an experimental, off-label fashion. Results were excellent. So he applied for Institutional Review Board approval of a clinical study and began enrolling patients a year ago. The criteria were:

Dr. Chapman enrolled nine patients. Treatment was simple: daily application for six weeks.

Two baseline punch biopsies took place on day zero: a histological one to confirm melanoma and another for cytokine analysis. At two weeks and six weeks, the dermatologist took additional cytokine biopsies. The final two biopsies (again, histological and cytokine) were taken at 12 weeks.

"The study is going very well. Five patients have completed and all lentigo maligna lesions have cleared. Four more patients remain in the study, and all of them are responding," Dr. Chapman reports.

Recommendations

Patients with lentigo maligna have a 5 percent to 10 percent chance of recurrence due, in part, to the fact that what is seen clinically sometimes fails to correspond with what pathologists are able to see under a microscope.

When pathology returns an ambiguous report on margins, dermatologists face a conundrum of whether to observe the area or to excise more tissue. Especially in those situations, Dr. Chapman recommends considering imiquimod as an adjuvant treatment option.

He adds that his preferred treatment protocol at present is 12 weeks of application for five days a week with weekends off.

Future research

Dr. Chapman anticipates that his first patient will be clear for four years as of February 2006, but emphasizes that "for this drug and tumor, five years of follow up data will be very important."

His next research goal is to build a database on the first 200 patients to meet the five year benchmark. To date, he has treated a total of 45 lentigo maligna cases (only one failed to respond) and is aware of another dozen or so cases in the U.S. That means the project will take him to Europe and other continents.

The direction of other research will depend on the cytokine findings, which will be tabulated after all patients complete the study.

Disclosure: Dr. Chapman consults for and performs research for 3M Pharmaceuticals.