KOH 5% solution versus diclofenac 3% for the treatment of actinic keratosis - Results from a three-armed RCT

Sep 23, 2026

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Actinic keratosis (AK) can progress to malignant cancer, making early, effective treatment important. This randomized controlled trial investigated potassium hydroxide (KOH) 5% solution versus diclofenac 3% gel and placebo for mild-to-moderate AK, focusing on efficacy and safety. Patients applied treatments twice daily for 28 days, followed by an off-treatment phase, with treatment success defined as complete clearance of all baseline lesions at end of treatment. Results showed higher success and complete remission with KOH, faster onset, and mostly mild, localized adverse reactions with comparable tolerability.

LanguageEnglish

CategoryHealthcare

FormatPDF

Pages9

Reading Time23 min

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Introduction

Methods

Results

Conclusions

DOI: 10.1111/jdv.70069 O R I G I N A L A R T I C L E KOH 5% solution versus diclofenac 3% for the treatment of actinic keratosis – Results from a three-armed RCT U. Reinhold1 | N. Leitz2 | R. Dominicus3 | E. L. Szabó4 | T. Dirschka5 | G. Popp6 | T. C. Fischer7 | N. Adamini8 | R. Ostendorf9 | M. Asefi10 | H. Durani11 | T. Hölting12 | U. Amann13 | F. Kreuziger14 | T. Assmann15 | H. Brüning16 | L. Freitag17 | K. Hoffmann18 | R. Gedschold19 Correspondence U. Reinhold, MVZ Dermatologisches Zentrum Bonn GmbH, Friedensplatz 16, Bonn 53111, Germany. Email: u.reinhold@derma-bonn.de Funding information InfectoPharm Arzneimittel und Consilium GmbH Abstract Background: Actinic Keratosis (AK) has the potential to progress into malignant cancer, thus necessitating timely and effective treatment. Despite several existing therapies, there is still a need for effective, well-tolerated therapeutic options, especially in the early treatment of patients with few isolated lesions in primary care. Objectives: To investigate the efficacy and safety of potassium hydroxide (KOH) 5% solution in comparison to diclofenac 3% gel and placebo for the treatment of mildto-moderate AK. Methods: In this randomized controlled trial, patients with mild or moderate AK applied KOH or placebo solution double-blinded twice daily for 28 days, followed by a 28-day off-treatment phase (1 treatment cycle) for up to three treatment cycles or until treatment success. In a third arm, diclofenac was applied twice daily for 60 days and evaluated investigator-blinded. The primary endpoint was treatment success, defined as complete clearance (CC) of all initially present AK lesions per patient atthe end of treatment (EOT). Results: In total, 631 patients were enrolled. Treatment success was achieved by 45.2% of patients treated with KOH, compared to 23.8% and 22.9% with diclofenac and placebo, respectively. Similarly, complete remission rates for individual lesions were higher with KOH (65.0%) than with diclofenac (45.9%) or placebo (39.9%). KOH showed a faster onset of action, with higher CC rates already after 1 month compared to diclofenac (16.0% vs. 9.2%) and converging efficacies after 6 months. Most adverse reactions were mild and localized, with comparable tolerability of KOH and diclofenac. Conclusions: KOH 5% solution proved superior to placebo and, when compared to diclofenac 3% gel, demonstrated significantly higher efficacy at EOT, as well as faster onset of action with comparable long-term efficacy and tolerability. KOH 5% solution is a valuable addition to the available treatment options for lesion-directed therapy in patients with mild-to-moderate AK. Clinicaltrials.gov Identifier: NCT 04552327. K E Y W O R D S actinic keratosis, diclofenac, lesion-directed therapy, potassium hydroxide | For affiliations refer to page 1057. | | --- | | This is an open access article under the terms of the Creative Commons Attribution-NonCommercial License, which permits use, distribution and reproduction in any medium, provided the original work is properly cited and is not used for commercial purposes.
© 2025 The Author(s). Journal of the European Academy of Dermatology and Venereology published by John Wiley & Sons Ltd on behalf of European Academy of Dermatology and Venereology. | [1050](1050 | wileyonlinelibrary.com/journal/jdv)[ |](1050 | wileyonlinelibrary.com/journal/jdv)[ wileyonlinelibrary.com/journal/jdv](1050 | wileyonlinelibrary.com/journal/jdv) J Eur Acad Dermatol Venereol. 2026;40:1050–1058. INTRODUCTION As a locally restricted carcinoma in situ, actinic keratosis (AK) is a common precursor of squamous cell carcinoma. The pathogenesis is associated with the proliferation ofatypical keratinocytes due to chronic, cumulative exposure to UV light.1 With a prevalence of 18% in Europe according to the latest data from the WHO, AK is becoming more common in recent years.2 The unpredictability of malignant transformation of

FAQs

What was the primary endpoint of the trial?

Treatment success was complete clearance of all initially present AK lesions per patient at the end of treatment (EOT).

How did KOH 5% perform compared with diclofenac 3% and placebo?

KOH achieved treatment success in 45.2% of patients versus 23.8% with diclofenac and 22.9% with placebo, and showed higher complete remission rates for individual lesions.

What did the study find about safety and tolerability?

Most adverse reactions were mild and localized, and tolerability of KOH and diclofenac was comparable.

Sep 23, 2026

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