A type of skin lesion called actinic keratosis, caused by long-term exposure to the sun, responds well to prescription Aldara cream applied three times a week in one or two month-long courses, a study shows. The cream contains a 5 percent concentration of the drug imiquimod.

In the study, reported in the Journal of the America Academy of Dermatology, this treatment successfully cleared all skin lesions in more than half of cases.

Actinic keratoses consist of abnormal skin cells, probably resulting from immune suppression caused by ultraviolet light, and they can sometimes become cancerous. Imiquimod stimulates the body’s own immune system to fight various conditions.

Dr. Joseph Jorizzo, at Wake Forest University School of Medicine in Winston-Salem, North Carolina, and associates designed their study to confirm preliminary findings that shorter courses of imiquimod may be as effective as the 16-week course approved by the US Food and Drug Administration.

“Most patients are not willing to undergo a 16-week course of treatment,” Jorizzo told Reuters Health. “Aldara has a lot of flexibility, so in the practical clinical setting, patients can use it exactly as we did in the paper, or they can compress the treatment even more.”

Patients with four to eight visible actinic keratoses located on the balding scalp or face were randomly assigned to treatment with imiquimod cream or to inactive sham-cream (the controls) applied three times per week for 4 weeks. There were 123 patients in each group.

Jorizzo and his colleagues report that, at a 4-week posttreatment evaluation, all skin lesions within the treatment area were cleared in 32 patients in the imiquimod arm but only 5 in the control arm.

Those with remaining lesions underwent a second 4-week course of treatment. Eighty-six patients in the imiquimod arm completed the second course, as did 113 in the control group. Among these subgroups, skin lesions cleared in 33 and 13 patients, respectively, at the second post-treatment check.

Overall, the skin lesions cleared up completely in 54 percent of patients in the imiquimod group but only 15 percent in the control group. The lesions partially cleared in 61 percent and 25 percent of cases, respectively.

Of patients who had completely cleared their skin lesions, 73 (59 in the imiquimod arm and 14 in the control arm) were evaluated at a 1-year follow-up. The recurrence rate was 39 percent in the imiquimod group compared with 57 percent in the control group, the researchers found.

“Actinic keratoses are traditionally considered to be precancerous, but really they’re not,” Jorizzo explained. “Their cells are transformed by exposure to the sun, cells with all the markers of squamous cell carcinoma, but they are kept in check by the immune surveillance system.” However, he noted, as one ages, and immunity declines, an actinic keratosis may progress to cancer.

Most dermatologists use cryosurgery or curettage (repeated scraping) to treat actinic keratoses, Jorizzo commented. “But that treatment destroys only the part of the lesion that one can see.” As an integrated approach to manage the condition, he recommends that imiquimod cream be used a week or two after the procedure “to flush out the remaining transformed cells.”

SOURCE: Journal of the American Academy of Dermatology, August 2007.