Actinic keratosis, or solar keratosis, results from the proliferation of atypical epidermal keratinocytes. When we can take the time to do a skin examination, we all see a lot of them especially among our older and middle-aged sun worshippers and sunscreen agnostics. My traditional approach, for better or for worse, has been to acquire the liquid nitrogen bottle on the floor and go to work. But my recent review of guidelines prepared on behalf of the British Association of Dermatologists and published several years ago have prompted me to open my eyes a bit more to other possible approaches.
Reassuringly, the likelihood of progression of an AK to squamous cell carcinoma (SCC) is low. Estimates from a large U.S. cohort revealed a rate of transformation to invasive or in situ SCC of 0.6% after 1 year and 2.6 % after 4 years. But we have to remember that although the progression rate is low, 60% of SCC arise from AKs.
The AK guideline authors synthesized and graded published evidence. Topical therapies receiving an "A grade" (i.e., good evidence) included no therapy or emollients for mild AKs and 5-fluorouracil. Therapies with a "B grade" (i.e., fair evidence) include diclofenac gel and imiquimod.
Other treatments include cryosurgery (A grade) and photodynamic therapy (B grade). We do a lot of cryotherapy in our practice but patients need to be informed of the scarring and possible hyper- or hypopigmentation that can occur with treatment. Photodynamic therapy will, in most cases, be administered by dermatologists.
According to a recent paper in the Drugs and Therapeutic Bulletin, patients should be referred to a dermatologist if there is diagnostic uncertainty, concerns about malignancy, treatment failure or management concerns, or if the patient is at high risk (e.g., organ transplant recipients, multiple large lesions, or previous SCC).
The guideline authors suggest that most patients can be evaluated and treated in the primary care setting. They go on to say that there is inadequate evidence to justify treatment of all AKs in an attempt to prevent malignant transformation. While reassuring, this requires us to consider all possible treatment approaches. One liquid nitrogen bottle does not fit all.
Dr. Ebbert is professor of medicine and general internist at the Mayo Clinic in Rochester, Minn., and a diplomate of the American Board of Addiction Medicine. The opinions expressed are those of the author. He reports no conflicts of interest.