Older patients with actinic keratosis at risk for cSCC

Diagnosis with actinic keratosis at age younger than 49 years or older than 80 years was associated with elevated cutaneous squamous cell carcinoma risk, according to a study.

“Risk of cutaneous squamous cell carcinoma (cSCC) after the diagnosis of actinic keratosis (AK) has not been studied during long follow-up periods,” Shabnam Madani, MD, of the department of dermatology and Mohs surgery at Kaiser Permanente, Walnut Creek, California, and colleagues wrote.

In the longitudinal cohort study, the researchers aimed to identify risk factors for cSCC over a 10-year period. They accrued 220,236 patients with AK and 220,236 controls matched for age, sex, race/ethnicity, medical center and date of diagnosis plus 30 days. Accrual occurred between Jan. 1, 2009, and Feb. 29, 2020, at Kaiser Permanente Northern California.

Incident cSCC served as the primary endpoint.

Subjects had a mean age of 64.1 years, and the cohort was 52.5% women.

Results showed that cSCC risk increased annually by 1.92% (95% CI, 1.89%-1.95%) among patients with AK but just 0.83% (95% CI, 0.81%-0.85%) among controls (subdistribution HR = 1.90; 95% CI, 1.85-1.95).

Diagnosis of AK at age 49 years or younger carried a nearly sevenfold risk for cSCC compared with individuals not diagnosed with AK (HR = 6.77; 95% CI, 5.50-8.32). Other age stratification data showed that compared with patients aged 49 years or younger at AK diagnosis, age 80 or more years at AK diagnosis yielded a significant increase in cSCC risk (HR, 8.18; 95% CI, 7.62-8.78).

Through 10 years of follow-up, the cumulative incidence of cSCC was 17.1% (95% CI, 16.9%-17.4%) in the AK group and 5.7% (95% CI, 5.5%-5.9%) in the control group.

Patients with 15 or more AKs were at an elevated cSCC risk compared with patients with just one AK (HR = 1.89; 95% CI, 1.75-2.04).

Older age was an important risk factor for cSCC development, as was white race, history of basal cell carcinoma and male sex, according to the findings.

Overall cSCC risk decreased over the course of the study. Findings showed that there was less cSCC during 2018-2019 than during 2009-2010 (HR = 0.67; 95% CI, 0.63-0.72).

“The results of this longitudinal cohort study can be used to develop recommendations to increase early detection of cSCC,” the researchers wrote. “Additional research is needed to understand the effect of AK treatment on cSCC risk and outcomes of cSCC.”