Background: Actinic keratosis (AK) is a common pre-malignant skin lesion that can progress to cutaneous squamous cell carcinoma (cSCC). Microwave therapy is an established cancer treatment and has been used for plantar viral warts.
Objectives: To evaluate the efficacy and feasibility of microwave as a treatment for AK.
Methods: Stage 1 was a dose-setting study, where seven participants had the dielectric properties of 12 thick and 22 thin AK assessed for optimisation of the microwave dose used for treatment in Stage 2. Stage 2 was a randomised, internally-controlled trial evaluating 179 AK in 11 patients (93 treated, 86 untreated controls) on the scalp/forehead or dorsal hand. Participants received one treatment initially and a repeat treatment to unresolved AK at week 4. Response was assessed at 6 visits over 4 months. The primary outcome was partial or complete resolution of the treated AK.
Results: A significantly higher proportion of treated AK areas responded than untreated ( 90% vs 13%; p-value < 0.001). Thin AK were more responsive than thick AK. Site did not affect efficacy. Pain was severe, but brief (80% reported pain lasting "a few seconds only"). Adverse effects were minimal (redness n=6, flaking n=3, itching n=3). All participants who would choose microwave therapy over their current treatment cited the shorter discomfort period.
Conclusions: Microwave therapy is a portable, safe and effective treatment for AK. An easy to deliver, acceptable therapy for AK is attractive as a prevention strategy. Whilst these results are promising, a larger randomised controlled trial is needed against an effective comparator to confirm clinical efficacy and patient acceptability.