There has been a trend among dermatologists to treat actinic keratosis with field therapy alongside what is termed lesion-directed therapy. What this means is that we are treating not just the individual lesions with cryotherapy (freezing the AK), but adding topical therapy, peels, Photodynamic therapy ( PDT), either before or after such treatment.
The term field cancerization has become popular in our literature. This means that large areas of the face bear atypical cells which can turn into actinic keratosis and then invasive squamous cell carcinoma. Treatment then should be meant to control the whole area and not merely one or two individual lesions.
We dermatologists feel that we should be aggressive in treating actinic keratoses, since in many ways they may be considered immature squamous cell carcinomas.
Most Squamous cell carcinomas demonstrate characteristics of AKs withoin them. Between 90-97 percent of SCCs have an AK either at its periphery or within it. Very frequently, when the pathologist has ascertained that we have excised the whole squamous cell, there is a note that actinic keratosis is found at the margin.
Studies have shown that 0.6% of Aks become a SCC after one year, 2.6% after four years and 13-20% after ten years.
Common genes and proteins have found in both Ak's and Squamous cell carcinomas. The p53 gene mutation is found in 69 % of squamous cell carcinomas and 53% of AKs. It is the p53 gene that arrests cell development when it detects an error in the DNA. This allows repair of that DNA or an orderly destruction of the cell entirely ( called apoptosis). When the p53 gene has mutated, it is abnormal and no longer can monitor cell behavior.
Of course, the major cause of these mutations is the sun ( UV exposure) and I guess tanning beds too as well as viruses ( HPV, and the more recently discovered Merkel cell polyomavirus. The sun decreases this immune surveillance system. Cells that have not divided properly continue divide crazily leading to cancer.
Three main topical treatments are currently used. ( There are some interesting plant derived topicals coming out of Australia also, we discussed these on our radio show).
The most well known, and the Grandaddy of the group, is 5-Fluorouracil ( Efudex, Fluroplex, Carac). This interferes with DNA ( deoxyribonucleic acid) and RNA (ribonucleic acid) synethesis ( (chromosome and protein formation basically). It also causes the death of rapidly growing cancer cells. 5 FU is found in a number of formulations and strengths. It is generally used twice a day for two-four weeks.
Imiquimod ( Aldara) causes the cellular release and proliferation of cytokines, proteins that spark the immune system and aid cellular communication. Aldara is generally used twice a day for 16 weeks.
The third commonly used topical is Diclofenac (Solaraze). Like its oral form, Voltaren, Diclofenac works by inhibiting the production of prostaglandins, chemicals of inflammation that can cause immunosuppression and cellular proliferation. This drug is applied twice a day for 60-90 days.
All three of these topicals, when used per FDA recommendation, give 50% clearance.
With photodynamic therapy ( PDT), the skin is exposed to a Blu-light or red light, following the application of a photosensitizer, either 5-aminoleulinic acid ( Levulan) or methylaminolevulinic acid respectively. This sensitizer is absorbed by abnormal cells and then zapped by the appropriate light source. This has the highest response rate of all: about 83%.
Some dermatologists are using combination treatment. For instance, in our office we like to have our patients use Aldara for a month, before and after PDT treatment. A recent paper showed that this modality has a 93% clearance rate.
Many of these therapeutic decisions should be determined by collaboration between physician and patient. PDT and Aldara can be a fairly rough experience. However, if a patient has repeated SCCs, or numerous AKs, it is my opinion that this should be the therapeutic choice.
Some patients prefer the slower and less disfiguring Diclofenac treatment. Others might want to "get it over with" and select Efudex or PDT. Some patients may be retired and elderly, less concerned with their appearance. Efudex might be the choice. A lawyer or TV reporter would certainly not want to walk around for three weeks with their face all ablaze. These folks would give the nod to Solaraze.
Now getting to your question ( sorry for being so long-winded). Peels are also an acceptable means of therapy. A study by Lawrence et al in the Archives of Dermatology, back in 1995 showed that a TCA 35% / Jessner's solution peel worked as well as a three week course of Efudex. Monheit has shown similar results.
For a peel to be effective it would have to be either a medium depth peel or a deep peel. These peels should not be attempted in darker skin types, but this type of skin rarely get a single actinic keratosis, never mind a whole field of them.
Of course, the advantage of the peel is that it is a one and done procedure like PDT ( without the Aldara supplement.).
The other advantage of the peel is the cosmetic benefit. Interestingly, a recent paper showed a nice photo-rejuvenation effect with Efudex also.
Of course, PDT is very well known for its photo-rejuvenation. Many cosmetic physicians offer this treatment for this use alone.
So yes peels can be used, but there is far more data regarding creams.