Patients with actinic keratosis (AK) have a nearly 2% per-year increased risk for cutaneous squamous cell carcinoma (cSCC) following initial AK diagnosis, study findings published in JAMA Dermatology suggest.

The study was performed from2009 to 2020. In this study, a total of 220,236 patients with AK and 220,236 matched control group patients (mean age, 64.1 years) without AK were followed for 10 years to identify rates of incident cSCC. Patients and control group patients were matched on age, sex, race and ethnicity, medical center, and date of initial AK diagnosis plus 30 days in those with AK. Pathologic data were used to obtain incident cSCC diagnosis.

In the cohort of patients who remained in the study over the 10-year follow-up period, the per-year risk for cSCC increased by 1.92% (95% CI, 1.89% to 1.95%) in patients with AK vs 0.83% (95% CI, 0.81% to 0.85%) in control group patients (subdistribution hazard ratio [HR], 1.90; 95% CI, 1.85-1.95).


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In a subpopulation of patients aged 49 years or younger, patients with AK were roughly 7 times more likely to receive a cSCC diagnosis during the follow-up period compared with patients without AK (HR, 6.77; 95% CI, 5.50-8.32).

The cumulative incidence rates of cSCC at the 10-year follow-up were 17.1% (95% CI, 16.9% to 17.4%) for patients with AK vs 5.7% (95% CI, 5.5% to 5.9%) for control group patients. There was a modest association between increased AKs and increased cSCC risk (≥15 AKs vs 1 AK: subdistribution HR, 1.89; 95% CI, 1.75-2.04).

Patients 80 years of age or older had a higher risk for cSCC during follow-up compared with patients 49 years of age or younger (subdistribution HR, 8.18; 95% CI, 7.62-8.78). Risk factors for cSCC in this study included AK, older age, White race, basal cell carcinoma history, and male sex.

The risk for cSCC decreased during the study period of 2009 to 2019, particularly from 2018 to 2019 vs 2009 and 2010 (subdistribution HR, 0.67; 95% CI, 0.63-0.72).

The investigators noted that a limitation of their study was the likelihood that some control group patients might have had undiagnosed AK, a possibility that could slightly affect the results.

The researchers emphasized that it continues to be “best practice to educate patients about the role of repeated sun exposure in damaging the skin and causing solar elastosis, AK, and skin cancer.”

Reference

Madani S, Marwaha S, Dusendang JR, et al. Ten-year follow-up of persons with sun-damaged skin associated with subsequent development of cutaneous squamous cell carcinoma. JAMA Dermatol. Published online March 24, 2021. doi:10.1001/jamadermatol.2021.0372