Patients with severe, Olsen grade III, actinic keratoses may have a 20.9% increased risk of subsequent invasive cutaneous squamous cell carcinoma (cSCC), and a third (33.5%) of those who need additional treatment for actinic keratoses go on to develop cSCC, according to a secondary analysis of a multicenter clinical trial from the Netherlands.

“Treatment of actinic keratoses aims to prevent [cSCC]. However, whether [actinic keratoses] can progress into invasive cSCC is a matter of debate, and little is known about the effect of treatment on preventing cSCC. […] These patients should be closely followed up after treatment,” wrote Shima Ahmady, MD, Department of Dermatology, Maastricht University Medical Center, the Netherlands and coauthors.

In the trial, 624 participants from 4 hospitals, with a minimum of 5 actinic keratoses within an area of 25 to 100 cm² on the head, were randomly assigned to treatment with 5% fluorouracil, 5% imiquimod cream, methylaminolevulinate photodynamic therapy, or 0.015% ingenol mebutate gel. Participants were excluded if they had received any kind of treatment for actinic keratoses in the past 3 months, had any skin cancer in the target area, an immunocompromised status, or used systemic retinoid or immunosuppressant medications in the prior 3 months (although the use of inhalation corticosteroids was permitted).

The median age was 73 years, and 89.4% of the participants were men. Long-term follow-up was performed from July 1, 2019, to December 31, 2020.

Of the entire cohort, 26 received a diagnosis of invasive cSCC in the target area during follow-up. The 4-year risk of developing cSCC in a previously treated area of actinic keratoses was 3.7% (95% CI, 2.4% to 5.7%), varying from 2.2% (95% CI, 0.7%-6.6%) in patients using fluorouracil to 5.8% (95% CI, 2.9% to 11.3%) in patients using imiquimod.

Source:
Ahmady S, Jansen MHE, Nelemans PJ, et al. Risk of invasive cutaneous squamous cell carcinoma after different treatments for actinic keratosis: a secondary analysis of a randomized clinical trial. JAMA Dermatol. Published online April 27, 2022. doi:10.1001/jamadermatol.2022.1034