INDIVIDUAL ARTICLE: Safety and Tolerability of Topical Agents for Actinic Keratosis: A Systematic Review of Phase 3 Clinical Trials

October 2021 | Volume 20 | Issue 10 | Supplement Individual Articles | s4s4 | Copyright © October 2021


Published online September 30, 2021

Jeffrey R. Rajkumar BSa, April W. Armstrong MD MPHb, Leon H. Kircik MDc

aUniversity of Illinois College of Medicine, Chicago, IL
bDepartment of Dermatology, University of Southern California, Keck School of Medicine, Los Angeles, CA
cIcahn School of Medicine at Mount Sinai, New York, NY; Indiana University Medical Center, Indianapolis, IN; Physicians Skin Care, PLLC, Louisville, KY; DermResearch, PLLC, Louisville, KY; Skin Sciences, PLLC, Louisville, KY

Abstract
Background: Topical agents for actinic keratosis (AK), along with cryotherapy and phototherapy, are the most commonly used therapies for areas of skin with multiple AKs. Multiple options for the topical treatment of AK exist; newer therapies aim to balance efficacy with an acceptable safety and tolerability profile for the patient.
Objective: To describe the safety and tolerability of FDA-approved topical agents for the treatment of AK.
Methods: A systematic review of phase III clinical trials of topical agents for AK available on PubMed and clinicaltrials.gov was conducted on January 10th, 2021.
Results: 29 phase III clinical trials meeting the inclusion criteria were included in the qualitative synthesis. No serious adverse events or systemic adverse events were determined to be due to topical therapies for AK. The highest rates of treatment-related application-site adverse events and local skin reactions occurred with the various formulations of topical 5-FU and imiquimod; newer topical agents such as ingenol mebutate and tirbanibulin had more favorable tolerability profiles.
Conclusions: FDA-approved topical agents for the treatment of multiple AKs have minimal safety concerns. Tolerability profiles vary among the available options, and new agents such as tirbanibulin offer a favorable combination of safety, tolerability, and efficacy.

J Drugs Dermatol. 2021;20:10(Suppl):s4-11.

INTRODUCTION

Actinic keratoses (AKs) are hyperkeratotic, erythematous papules or plaques with overlying scale and rough texture found in sun-damaged areas of skin.1 They represent a chronic and recurring manifestation of field cancerization. AKs are most commonly diagnosed in fair-skinned individuals,2 and incidence increases with age and exposure to UV radiation.1 An analysis of the National Ambulatory Medical Care Survey (NAMCS) data from 1993–2010 found that 14.6% of dermatologist visits included a diagnosis of AK.3 Data pooled from several nation-wide surveys estimated the prevalence of AK in the United States to be 39.5 million in 2004.4

Areas of clinically sun-damaged skin are predisposed to tumorigenesis; this phenomenon is referred to as field-cancerization.5 In areas of skin with extensive sun-damage and/or multiple AKs, topical agents may be prescribed to treat overt lesions and prevent subclinical dysplasia from progressing to AK.5,6 AKs themselves may progress to squamous cell carcinoma (SCC); however, there are no clinical features unique to AK lesions which predict this transformation, and data regarding the rate of progression from AK to SCC are inconclusive.7 Therefore, the common consensus is to treat all AK lesions to prevent transformation to SCC.8 Multiple treatment modalities exist for the treatment of AK. Cryotherapy or excision may be used for individual AK lesions (lesion-directed therapy), and topicals or photodynamic therapy may be used in diffusely sun-damaged skin containing both overt and subclinical lesions (field-directed therapy).8

Topical agents have been used for the treatment of multiple AKs from the 1960s, beginning with the use of topical fluorouracil (5-FU). Dillaha et al in 1963 reported successful clearance of multiple AKs using a 20% 5-FU solution; however, patients also experienced severe inflammation, erosions, corneal and conjunctival irritation, and photosenstivity.9 Milder preparations of 5-FU and new topical agents for AK, such as the antimitotic agent tirbanibulin, have maintained treatment efficacy while substantially improving tolerability.10 The purpose of this review is to document the safety and tolerability of topical agents used for the treatment of AK.