5-fluorouracil not superior to imiquimod in long-term cSCC prevention

Despite prior evidence of excellent actinic keratosis (AK) destruction efficacy, 5-fluorouracil (5-FU) does not appear to be better than imiquimod in the prevention of cutaneous squamous cell carcinoma (cSCC), reports a recent study.

However, 5-FU shows superiority over photodynamic therapy with aminolevulinic acid (PDT-ALA).

“Studies comparing 5-FU, imiquimod, and PDT-ALA have evaluated the efficacy of destroying AK,” the authors said. “However, this endpoint may not directly translate to cSCC prevention.”

This retrospective cohort study was conducted to examine these field therapies for cSCC prevention in the long term, which was defined as >1-year post-treatment. The authors used the Optum Clinformatics Data Mart database from 2012 to 2019 and determined the time to surgically treat invasive cSCC development after treatment with 5-FU, imiquimod, or PDT-ALA beginning 1-year post-treatment.

No significant difference was observed in the rate of cSCC development in patients treated with 5-FU relative to those who received imiquimod (hazard ratio [HR] 0.99, 95 percent confidence interval [CI], 0.90‒1.08). Moreover, PDT-ALA was worse than both 5-FU (HR, 1.27, 95 percent CI, 1.19‒1.36) and imiquimod (HR, 1.29, 95 percent CI, 1.17‒1.43).

Of note, other established predictors of cSCC were consistent with previous literature.

One limitation of the current study was the failure to identify the location of field therapy with the use of a claims database.

“Conflating AK destruction and cSCC prevention efficacy may not be appropriate,” the authors said. “Future prospective studies should aim to use an endpoint of cSCC development.”