Efficacy and Safety of LEO 43204 in Field Treatment of Actinic Keratosis on Balding Scalp Including 12-month Follow-up

Inclusion Criteria: * Subjects with 5 to 20 clinically typical, visible and discrete AKs within a treatment area of sun-damaged skin on the full balding scalp (the balding part of the scalp should be greater than 25 cm2 (4 in2) and up to approximately 250 cm2 (40 In2) * Subjects with minimum 3 clinically typical, visible and discrete AKs within a tracking area of 50 cm2 (8 In2). The tracking area must be within the treatment area Exclusion Criteria: * Location of the treatment area (full balding scalp) within 5 cm of an incompletely healed wound or within 5 cm of a suspected BCC or SCC * Treatment with ingenol mebutate gel in the treatment area within the last 12 months * Lesions in the treatment area that have: atypical clinical appearance (e.g. hyperthrophic, hyperkeratotic or cutaneous horns) and /or, recalcitrant disease (e.g. did not respond to cryotherapy on two previous occasions) * History or evidence of skin conditions other than the trial indication that would interfere with the evaluation of the trial medication (e.g. eczema, unstable psoriasis, xeroderma pigmentosum)