Efficacy And Safety Of Illumination Dose Reduction In Red Light Photodynamic Therapy For Actinic Keratoses

The goal of this clinical trial is to compare the tolerance and efficacy of conventional photodynamic therapy (PDT) with red light versus PDT with red light at half dose of illumination, as well as the changes produced by both interventions at the biomolecular level in patients with multiple actinic keratosis on the scalp. The main questions it aims to answer are:

Does PDT with half-dose illumination protocol maintain clinical and biomolecular efficacy?

Does PDT with half-dose illumination protocol improve intervention tolerance?

Researchers will compare both treatment protocols using the patient as its own control.

Participants scalp will be divided in two halves, one will be treated with PDT at conventional doses and the other with the half-dose illumination protocol, a skin biopsy will be obtained both pre and post-treatment of each of the areas. Variables will be assessed during the 3 visits of the study.

The goal of the clinical trial is to compare efficacy and tolerance of photodynamic therapy (PDT) with red light at half dose illumination protocol with conventional PDT for the treatment of grade I and II actinic keratosis. The main hypotheses is that half-light protocol PDT could maintain efficacy while improving tolerance of the procedure.

With this aim the investigators will compare the efficacy of the clinical response after field treatment with photodynamic therapy with red light at half dose versus conventional photodynamic therapy with standard red light in patients with scalp actinic keratoses as well as determine changes in molecular biomarkers at the histological and immunohistochemical level pre- and post-treatment with conventional PDT and PDT with red light at half dose.

The included patients will have their scalp divided into two halves of similar size using the interparietal line as a separation method; one half will be treated with conventional PDT and the other half with half-dose PDT. This is a comparative study between two treatment modalities, both of which will be applied to all patients, and in half of the sample, four skin biopsies of the affected area (two pre and tw post-treatment) will also be performed to conduct an immunohistochemical analysis of the skin samples. Both treatment protocols will be compared using the patient as his or her own protocol. Variables will be assessed during the 3 visits of the study (baseline, 3 months and 6 months).

Eligibility Criteria:
Inclusion Criteria:

* Patient with grade I and II actinic keratoses (AK) of Olsen on the scalp requiring field cancerization treatment.
* ≥ 18 years old.
* More than 5 AK per field of cancerization to be treated.
* More than 6 months since the last field treatment for AK performed.
* No AK in clinical grade III progression of Olsen or showing signs suggestive of being invasive squamous cell carcinoma.

Exclusion Criteria:

* Patients with photodermatoses.
* Patients sensitive to methyl-aminolevulinate.
* Patients with disabilities or unable to provide informed consent.
* Patients who do not tolerate or do not wish to be treated with PDT.