Photodynamic Therapy for Melanoma Precursor Lesion Lentigo Maligna Using 5-aminolevulinic Acid Nanoemulsion (BF-200 ALA) as a Light Sensitizing Cream

Lentigo maligna (LM) is an in-situ form of melanoma which occurs on sun-exposed skin. Untreated LM can progress into invasive lentigo maligna melanoma (LMM). The incidence of LM/LMM is constantly increasing as the population grows older and lifelong sun-exposure is on the rise. Clinically it is difficult both to determine the borderline of LM as well as to differentiate LMM from LM. A novel imaging method hyperspectral imaging system (HIS) can be used for delineating margins of LM and for spotting invasion inside LM lesion. The gold standard treatment for LM is surgical excision with adequate (≥5 mm) margins. Due to large size of LM lesions and typical location on face or neck the surgical treatment is challenging and can cause aesthetic and functional deficit for the patient. Furthermore, LM patients tend to be elderly who may have anesthetic contraindications. Other treatment modalities for LM have been studied but none of them still has proved to be efficient enough. Recently, photodynamic treatment (PDT) has been suggested as a promising novel treatment method for LM.

In this prospective pilot study we investigate whether the photodynamic therapy (PDT) is effective for treatment of lentigo maligna. 10-15 patients with a histologically confirmed lentigo maligna are included in the trial. The study course is as follows: During the first visit in the clinic, the suspected LM lesion is examined clinically under Wood's lamp and imaged with a HIS camera. Elicited margins from both methods are marked on a transparent sheet and the treatment area is photographed. A biopsy is taken from the darkest-colored part of LM to confirm diagnosis and to rule out invasion. Next, the patients receive PDT treatment three times with 2 weeks' intervals. Before applying the Ameluz® light sensitizer gel the skin of treatment area is prepared with fractional ablative CO2-laser to enhance absorption. After light sensitizer absorption the LM lesion is illuminated with artificial red light (Aktilite CL128 lamp) using a light dose of 90 J/cm2. Finally 4 weeks after the last PDT treatment LM is excised surgically using 5 mm margins. The efficacy of PDT is assessed after surgical excision with histopathological examination and immunohistochemical staining (MART, Mel-5 and MITF stains). The final result of the treatment is controlled 6 months after the surgical excision.