Association Between Local Skin Reactions and Efficacy with 5-Fluorouracil 4% Cream in Actinic Keratosis: A Post-Hoc Analysis of Two Randomised Clinical Trials.

Introduction: Topical 5-fluorouracil (5-FU), 5% or 4% cream, is recommended among first-line treatments for actinic keratosis (AK). Local skin reactions (LSRs) are an expected and transient response to treatment with 5-FU but can lead to treatment discontinuation when severe. This analysis aimed to investigate whether the severity of LSRs during the treatment was associated with lesion clearance assessed 4 weeks after completing treatment.