Background: 5% 5-fluorouracil cream (5-FU) is a well-established treatment for actinic keratosis (AK) and ingenol mebutate gel (IMB) is a new topical field therapy.

Objective: To compare tolerability and safety of IMB with 5-FU for the treatment of facial AKs.

Methods: Open-label, prospective, randomized, controlled clinical trial with 100 patients with AKs within 25-cm2 contiguous field on the face. IMB was applied daily for three consecutive days. 5-FU was applied twice a day for four weeks. Treatment effect was evaluated at baseline and on days 2, 3, 4, 8, 15, 22, 29, 36 and 43, considering ITT populations.

Inclusion Criteria:

• age of at least 18 years
• the presence of four to eight clinically typical, visible, and discrete AKs within 25-cm2 contiguous field on the face (cheek or forehead region)
• Women with childbearing potential had to be using effective birth control and have a confirmed negative urine pregnancy test prior to trial treatment.

Exclusion Criteria:

• target treatment area was within 5 cm of an incompletely healed wound or within 10 cm of a suspected basal-cell or squamous-cell carcinoma
• if they have received previous treatment with ingenol mebutate gel on the face or scalp (previous treatment on trunk or extremities was acceptable)
• the selected treatment area had hyperkeratotic lesions or cutaneous horns and recalcitrant disease (lesions that had not responded to cryotherapy on two previous occasions)
• history or evidence of skin conditions that would interfere with the evaluation of the trial medication (e.g., eczema, unstable psoriasis, xeroderma pigmentosum)
• anticipated need for hospitalization or outpatient surgery during the first 15 days after the first trial medication application
• known sensitivity or allergy to any of the ingredients of ingenol mebutate gel or 5-FU
• presence of sunburn within of the target treatment area; current enrolment or participation in any other interventional clinical trial within 30 days of entry into this trial
• women breastfeeding
• recent use of medications or other treatments that could interfere with evaluation of the target area, such as topical medications (e.g. steroids, keratolytics, immunomodulators), artificial tanners, immunomodulators, cytotoxic drugs or interferon /interferon inducers, phototherapy, systemic retinoids, biologic/monoclonal antibody drugs, or other therapies for AKs within eight weeks prior to the first visit of the trial.