Currently available topical therapies for actinic keratosis offer short-term clearance, but the initial robust efficacy of these agents tends to wane by 12 months, according to research findings published in Australasian Journal of Dermatology. Likewise, many studies on available topical therapies used in skin field cancerization have relatively short follow-up periods, limiting the understanding of how well these therapies clear lesions over the long term.
The research was part of a literature review study which examined the efficacy of commonly used topical treatments for actinic keratosis and skin field cancerization in clinical research. According to the researchers of the review, there appears to be a “significant lack of high-quality” randomized trials on the effectiveness of these topical therapies for these conditions, and the durability of treatment outcomes has also not yet been fully elucidated.
Studies seem to use different outcome measures to compare topical therapies, and this lack of uniformity in outcome assessment may hinder conclusions in published research, the investigators noted. Outcome measures across studies include clearance of target lesions only, percentage change in area of actinic keratosis coverage, percentage change in actinic keratosis numbers, as well as the number of patients with either a partial (>75%) or complete (100%) field clearance.
Of the studies that reported 12-month clearance counts compared with baseline, 5-FU and imiquimod appeared to provide the best efficacy for skin field cancerization. In addition to imiquimod and 5-FU, other treatments such as diclofenac, ingenol mebutate, and aminolevulinic acid/photodynamic therapy were associated with relatively high rates of percentage cleared at 3 to 6 months. However, these clearance rates largely reduced by 12 months. Similar reductions in the percentage of patients who achieved total field clearance of actinic keratosis were observed at the 3- and 12-month follow-up periods.
Studies included in this review focused solely on the face and scalp, thereby limiting the findings to these areas and omitting other areas of the body that experience worse outcomes, such as the upper limbs.
The researchers wrote that many of the studies in this review on topical therapies for actinic keratosis and skin field cancerization feature short follow-up data. “The acceptance of such short follow-up data may have the downside of not providing real-world evidence,” the researchers added.
In addition, the investigators explained that “if the rationale behind field therapy is to reduce long-term cancer incidence, the available evidence for most agents supports a short- to medium-term benefit only,” further warranting “the need for ongoing surveillance with repeated treatments.”
Sinclair R, Baker C, Spelman L, Supranowicz M, MacMahon B. A review of actinic keratosis, skin field cancerisation and the efficacy of topical therapies. Australas J Dermatol. 2021;62(2):119-123.