Actinic Keratoses: A Prospective Pilot Study on a Novel Formulation of 4% 5-Fluorouracil Cream and a Review of Other Current Topical Treatment Options

Background: Actinic keratosis (AK) is one of the most common skin diseases, with a low risk of progression into invasive squamous cell carcinoma. We aim to assess efficacy and safety of a novel formulation of 5-Fluorouracil (5-FU) 4% with once daily application for the treatment of multiple AKs. Methods: A pilot study was performed on 30 patients with a clinical and dermoscopic diagnosis of multiple AKs, enrolled between September 2021 and May 2022 at the Dermatology Departments of two Italian hospitals. Patients were treated with 5-FU 4% cream once daily for 30 consecutive days. The Actinic Keratosis Area and Severity Index (AKASI) was calculated before starting therapy, and at each follow-up, to assess objective clinical response. Results: The cohort analyzed included 14 (47%) males and 16 (53%) females (mean age: 71 ± 12 years). A significant decrease in AKASI score at both 6 and 12 weeks (p < 0.0001) was observed. Only three patients (10%) discontinued therapy, and 13 patients (43%) did not report any adverse reactions; no unexpected adverse events were observed. Conclusions: In the setting of topical chemotherapy and immunotherapy, the new formulation of 5-FU 4% proved to be a highly effective treatment for AKs and field cancerization.