Imiquimod/LN effective treatment for some skin cancers

May 1, 2006

Houston - For the general dermatologist, the mainstay of safeand effective skin cancer management is dependent upon sensibleclinical judgment, says Deborah MacFarlane, M.D., associateprofessor of dermatology and plastic surgery at the University ofTexas Medical School at Houston, and MD Anderson Cancer Center.

Houston - For the general dermatologist, the mainstay of safe and effective skin cancer management is dependent upon sensible clinical judgment, says Deborah MacFarlane, M.D., associate professor of dermatology and plastic surgery at the University of Texas Medical School at Houston, and MD Anderson Cancer Center.

"This base, combined with a knowledge of the efficacy of the various modalities now available on the market, will help the clinician to successfully manage future skin cancers," she says.

Dr. MacFarlane says that she has found one of these treatment modalities - imiquimod combined with liquid nitrogen (LN) - to be highly effective in managing certain forms of skin cancer.

Field cancerization, field therapy

Dr. MacFarlane says that studies using imiquimod for the treatment of AKs call for two- to three-times weekly applications for four to 16 weeks and have shown an 80 percent or higher complete clearance rate at two- to 12-month follow-ups.

"In patients with significant photodamage, surrounding skin has been found to contain clones of transformed cells and subclinical AKs, a concept known as 'field cancerization,'" she says. "Imiquimod usage has been noted to cause such subclinical lesions to become clinically apparent and treatment responsive, demonstrating 'field therapy.' There is evidence that imiquimod is also effective for the treatment of sBCCs and also squamous cell carcinoma (SCC) in situ."

Combination therapy

During her six-year study, Dr. MacFarlane has been using a combination of LN and imiquimod to treat AKs, sBCCs and SCC in situ. She says lesions were first treated with an application of LN and then, one week later, patients applied imiquimod to the area per the regimen for their particular diagnosis. This treatment had significant positive impact, she says.

"Combining two modalities gives me more confidence that the lesion was treated, involving patients in their own cancer management led to improved outcomes, and areas to treat were highlighted by the LN, reducing patient confusion," Dr. MacFarlane tells Dermatology Times.

Patients were seen three weeks into the imiquimod course to ensure compliance, and again at the conclusion of their six-week treatment, according to Dr. MacFarlane. Baseline biopsies were taken of all sBCCs and SCC in situ and many AKs prior to treatment. Follow-up biopsies were performed in these same patients at the conclusion of their treatment.

"It became apparent during the first six months of the study that only six weeks of imiquimod treatment were needed for the successful treatment of these lesions," she says. "It was also apparent that especially for AKs, treatment could be titrated to tolerability to maximize compliance, comfort and efficacy. While four- and five-year follow up is available on some of the patients, most have now been followed for three to four years."

Dr. MacFarlane says she does not recommend this treatment for recurrent lesions, for SCC in situ with follicular involvement, for lesions in densely hair-bearing areas or those in the periocular area.

"Perhaps because patients are seen midway through their therapy, excess irritation is surprisingly rare," she says. "In those cases where it occurs, imiquimod should be stopped immediately. The inflammation can be treated with a topical antibiotic ointment and the skin occluded if broken. In case residual cancer is present, topical steroids are not advocated, and, also, there is a theoretical concern that they might have an immunosuppressive effect, reducing the efficacy of any residual response from imiquimod. Oral anti-inflammatories can be used to treat painful lymphadenopathy."