What is the role of 5-fluorouracil (5-FU) in the treatment of actinic keratosis?

Updated: Jan 23, 2020
  • Author: James M Spencer, MD; Chief Editor: William D James, MD  more...
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Answer

The most experience in topical therapy for actinic keratoses is with 5-FU, known to inhibit thymidylate synthetase and cause cell death in actively proliferating cells. [43] Several formulations are available, including a 5% cream or solution, a 2% solution, a 1% cream or solution, and, most recently, a micronized 0.5% cream. [11] Although not well studied, efficacy among the various formulations does not seem to differ significantly. [44, 45]

The most popular formulation is the 5% cream, which is applied twice daily for 1 month. During the treatment phase, the lesions become increasingly erythematous and cause discomfort; small subclinical lesions become visible. This treatment can be temporarily disfiguring, with erythematous ulcerations and crust formation. However, if the patient completes the treatment, the lesions usually heal within 2 weeks of stopping treatment, the complexion is smooth, and the actinic keratoses are improved.

The 0.5% micronized cream was developed to increase tolerability because inflammation and discomfort can be a limiting factor in the use of topical 5-FU. The 0.5% micronized cream is applied once daily for 1 month.

Usage of the 0.5% micronized cream 1 week prior to cryosurgery has also been shown to produce complete lesion clearance in a higher number of patients compared with cryosurgery alone (32.4% and 15%, respectively). [46] Note the images below.

Actinic keratosis during treatment with topical 5- Actinic keratosis during treatment with topical 5-fluorouracil. Courtesy of Hon Pak, MD.
Actinic keratosis right after treatment with topic Actinic keratosis right after treatment with topical 5-fluorouracil. Courtesy of Hon Pak, MD.

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