NEW YORK (Reuters Health) - Applying a prescription cream (imiquimod) for 24 weeks is effective for the treatment of a type of skin lesion called actinic keratosis, caused by long-term exposure to the sun, according to researchers from Mount Sinai Medical Center in New York.

Dr. Mark Lebwohl and colleagues enrolled 20 patients with actinic keratosis into a 28-week trial. Fifteen patients completed the trial and five dropped out for reasons unrelated to treatment, the researchers report in the Journal of the American Academy of Dermatology.

Patients applied imiquimod 5 percent cream supplied in 250 milligram single-dose packages to affected areas on one side of the body and a placebo cream to the opposite side once a week for 24 weeks. Patients were assessed at 28 weeks.

Seven patients, or 46.7 percent, had marked improvement or better on the actively treated areas, while only one patient (6.7 percent) had improvement in areas treated with the placebo cream, the researchers report.

The total number of lesions declined from an average of 1.93 to 1.47 on the actively treated side, while the number increased from 2.07 to 2.13 on the placebo side.

Of lesions treated with imiquimod cream, five of five mild cases remained mild; two of six moderate cases remained moderate, three improved to mild and one cleared; and three of four severe cases remained severe, while one improved to mild.

Of lesions receiving placebo, one of three mild cases remained mild, while two worsened to moderate; seven of eight moderate cases remained moderate, while one improved to mild; and all eight cases rated as severe at baseline remained severe at follow-up.

Side effects with imiquimod cream were minimal to nonexistent.

"We have used imiquimod once per week in routine clinical practice for periods over 1 year with good outcomes," Lebwohl told Reuters Health. "Mild redness is the main side effect and, with successful therapy, that fades."

SOURCE: Journal of the American Academy of Dermatology, January 2009.