This study compares the efficacy and tolerance of a new device (FLEXITHERALIGHT) for photodynamic therapy in the treatment of keratosis actinic in comparison of classical PDT with Aktilite®.

The study is an intraindividual comparison of two methods. The number of subjects to be enrolled is 47 patients. All participants will receive both two treatments in a single visit : a first period of 2.5 hours of illumination with FLEXITHERALIGHT device followed by a continuous red light Spectrum (between 7 and 10 minutes) with Aktilite® after an appropriate incubation of methyl aminolevulinate).

Patients will complete a pain assessment scale after receiving both treatments, then, 3 follow up visits will be scheduled.

Inclusion Criteria:

• Clinical diagnosis of minimum 10 previously untreated not pigmented, non-hyperkeratotic AK lesions of Grade I and II of the forehead and/or scalp (according to Olsen et Al. JAAD 1991, cf. REF 31) where other therapies are unacceptable or considered medically less appropriate with a symmetrical repartition on both side of the forehead and/or scalp. The diagnosis of AK will be determined upon clinical evaluation (i.e. visual inspection and palpation) by the investigator.
• Symmetrical areas in terms of number and severity of lesions. The axis of symmetry between the two areas will be defined by the investigator according to the distribution of lesions.
• The two areas to be treated should not be coalescing. A minimum distance of 10mm is required between the lesions located on the 2 symmetrical areas. A minimum distance of 2 mm is required between the lesions on the same side.
• Minimum 5 lesions with similar dimensions at both symmetrical areas will be treated. If the number of lesions is >7, only 7 lesions on each side will be considered.

Exclusion Criteria:

• Patients with porphyria.
• Patients immunosuppressed for idiopathic, disease specific or therapeutic reasons.
• Use of topical corticosteroids to lesional areas within 2 weeks before PDT.
• Patients receiving local treatment (including cryotherapy and curettage, any - Patients receiving topical treatment (including imiquimod, 5-FU and diclofenac, Picato) in face / scalp area within the last 3 months.
• Use of topical retinoids or alpha-hydroxy acids, urea or systemic retinoids, chemotherapy or immunotherapy within 4 weeks of PDT.
• Pigmented AK lesion(s).
• Known allergy to Metvixia, a similar PDT compound or excipients of the cream including arachis oil, or to peanut or soya.
• Participation in other clinical studies either currently or within the last 30 days.
• Female subjects must be of either:

Non-childbearing potential, i.e. post-menopausal or have a confirmed clinical history of sterility (e.g. the subject is without a uterus) or, Childbearing potential, provided there is a confirmed negative urine pregnancy test prior to study treatment, to rule out pregnancy.

• Any condition which may be associated with a risk of poor protocol compliance.
• Patients currently receiving regular ultraviolet radiation therapy