San Francisco - The difficulty of treating multiple actinic keratoses (AKs) and squamous cell carcinomas (SCCs) on the legs demands that dermatologists consider multiple modalities and monitor patients closely for invasive SCC, an expert says.
- The difficulty of treating multiple actinic keratoses (AKs) and squamous cell carcinomas (SCCs) on the legs demands that dermatologists consider multiple modalities and monitor patients closely for invasive SCC, an expert says.
Though multiple AKs and SCCs occur most commonly on the head and neck, "They also occur on the lower extremities," particularly in females, says Michel A. McDonald, M.D., M.B.A., director of cosmetic dermatology surgery and Mohs micrographic surgery at Vanderbilt University, Nashville.
Such patients often possess a history of prolonged tanning, while radiation exposure represents another common denominator. One patient she has treated played extensively with an x-ray machine as a child, Dr. McDonald says.
In treating multiple AKs and SCCs in such patients, she says that because definitive answers remain elusive, "I try everything."
More specifically, she says cryotherapy can be effective for smaller numbers of AKs. "In a large retrospective review of 1,000 AKs treated with this therapy, 98 percent cured at one year."
However, Dr. McDonald notes, "The problem with cryosurgery is that it doesn’t allow for field treatment. And when the patient has 20 or 30 (lesions) on the lower extremities, it’s hard to utilize cryosurgery alone."
Imiquimod and 5-fluorouracil (5-FU) allow for field treatment, as well as greater patient control of therapy, she says.
Although various studies support different treatment regimens, Dr. McDonald says, "I tend to prescribe imiquimod three days a week for 16 weeks. But I’ll often do cyclic therapy - four weeks on, four weeks off. And we’ll do different areas of the legs, not the whole leg at once."
Patients frequently require multiple 16-week cycles, she adds. With 5-FU, "I tend to prescribe five percent cream twice a day for two to four weeks."
Because patients can experience intense responses to this drug, "I’ve had to discontinue it on the legs as field treatment, and I rarely use it as field treatment over the entire leg at once."
Both imiquimod and 5-FU can achieve high AK clearance rates, Dr. McDonald says, "But I worry in these patients - am I treating AK or SCC?"
To help ensure that she isn’t missing invasive SCC, she performs periodic biopsies in patients undergoing multiple courses of treatment. Her preferred treatment choices for invasive SCC include desiccation and curettage, and Mohs surgery.
Photodynamic therapy (PDT) has achieved clinical clearance rates between 68 percent and 75 percent for AKs located on the head and neck, Dr. McDonald says. But when used on the lower extremities, many patients experience partial or no response.
Accordingly, she says, "Patient selection is very important. Hyperkeratotic AKs do not respond as well."
She suggests pretreating these AKs with curettage, imiquimod or 5-FU before applying PDT. Occlusion helps the aminolevulinic acid photo sensitizer to penetrate more effectively.
"Sometimes I’ll also treat patients after PDT with imiquimod. Often, PDT is not the only thing I'm doing," Dr. McDonald says. DT