Ablative fractional laser-assisted photodynamic therapy for lentigo maligna: a prospective pilot study

Lentigo maligna (LM) is an in situ form of melanoma carrying a risk of progression to invasive lentigo maligna melanoma (LMM). LM poses a clinical challenge, with subclinical extension and high recurrence rates after incomplete surgery. Alternative treatment methods have been investigated with varying results. Photodynamic therapy (PDT) with methylaminolaevulinate (MAL) has already proved promising in this respect.

To investigate the efficacy of ablative fractional laser (AFL)-assisted PDT with 5-aminolaevulinic acid nanoemulsion (BF-200 ALA) for treating LM.

In this non-sponsored prospective pilot study, ten histologically verified LMs were treated with AFL-assisted PDT three times at 2-week intervals using a light dose of 90 J/cm² per treatment session. Local anaesthesia with ropivacaine was used. Four weeks after the last PDT treatment the lesions were treated surgically with a wide excision and sent for histopathological examination. The primary outcome was complete histopathological clearance of the LM from the surgical specimen. Patient-reported pain during illumination and the severity of the skin reaction after the PDT treatments were monitored as secondary outcomes.

The complete histopathological clearance rate was 7 out of 10 LMs (70%). The pain during illumination was tolerable, with the mean pain scores for the PDT sessions on a visual assessment scale ranging from 2.9 to 3.8. Some severe skin reactions occurred during the treatment period, however.

Ablative fractional laser-assisted PDT showed moderate efficacy in terms of histological clearance. It could constitute an alternative treatment for LM but due to the side effects it should only be considered in inoperable cases.