For patients with actinic keratosis (AK) lesions, the risk for invasive cutaneous squamous cell carcinoma (cSCC) is increased for those with severe AK and especially for those who require additional treatment, according to a study published online April 27 in JAMA Dermatology .

Shima Ahmady, M.D., from Maastricht University Medical Center in the Netherlands, and colleagues examined the risk for invasive cSCC and factors that may contribute to increased risk among patients with multiple AKs. Participants included 624 patients with a minimum of five AKs within an area of 25 to 100 cm ² on the head, who were randomly assigned to treatment with 5 percent fluorouracil, 5 percent imiquimod cream, methylaminolevulinate photodynamic therapy, or 0.015 percent ingenol mebutate gel.

The researchers found that during follow-up, 26 patients were diagnosed with a histologically proven invasive cSCC in the target area. The total four-year risk was 3.7 percent for developing cSCC in a previously treated area of AK and varied from 2.2 to 5.8 percent for patients treated with fluorouracil and imiquimod, respectively. The risk was 20.9 percent in patients with severe AK (Olsen grade III) and was especially high (33.5 percent) for those with severe AK who needed additional treatment.

"The risk of invasive cSCC was highest in patients with Olsen grade III AK lesions and was substantially increased in patients who received additional treatment," the authors write. "We therefore recommend close follow-up of these patients."

One author disclosed financial ties to the pharmaceutical industry.

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