Intralesional Diode Laser Treatment of Fistulas in Hidradenitis Suppurativa

Background and aim:

Hidradenitis suppurativa (HS) is a common chronic skin disease that manifests by intermittent flare-ups of inflamed painful nodules that often leave mutilating scars, chronic suppurating tunnels and a changed microbiome compared to normal skin. Symptoms typically begin during adolescence and patients struggle with pain, pruritus, malodor and purulent discharge compromising work life, physical exercise, and sexual habits. Consequently, the risk of social exclusion, anxiety, depression and suicide is increased among patients suffering from HS.

Topical and systemic medical treatments, e.g. in the form of antibiotics, vitamin A derivates, immune-modulatory drugs or biological therapies aim to control inflammation. Once fistulas have formed, surgical intervention is often required. Present surgical therapies comprise surgical deroofing where the fistulas are cut open and left to heal, removal of specific pathological structures by ablative laser surgery or complete surgical removal en bloc of affected HS skin followed by skin grafting.

Recently, emergence of flexible diode laser fibers has enabled intra-lesional laser treatments of fistulas and the technique has been applied for e.g. perianal fistulas. Two prospective and one retrospective cohort studies evaluated a total of 265 patients treated with 1470 nm laser fiber surgery for perianal fistulas, demonstrating primary healing with absence of symptoms after one treatment in 40% to 71% of patients, a median healing time of 5 weeks, and long-term closure beyond 12 months in 71% of patients6. Intralesional laser fiber treatment has also been tested in HS tunnels. One study of concomitant 630 nm laser fiber treatment and photodynamic therapy has demonstrated a significant reduction in hidradenitis severity score and complete response in 47 % of patients after one treatment session.

Intralesional flexible laser fibers have also been tested in the treatment of HS tunnels without concomitant photodynamic therapy. One study investigated four sessions of 1064 nm intralesional diode laser therapy performed in local anesthesia. In a total of 20 patients, a significant reduction of Sartorius score and improved quality of life was demonstrated. No patients experienced neither worsening of disease nor complete cure and adverse effects were mild and transient. It was proposed, that intralesional laser treatment may elicit a decontaminating as well as an denaturing effect. Histological evaluation of endo-venous 1470 nm laser fiber treatment have demonstrated uniform coagulation without carbonization. Overall, the intralesional laser fiber technique is still new, and knowledge of optimal laser wave lengths, energy levels, number of treatments and treatment intervals is sparse. In addition, little is known about laser-tissue interactions in vivo as well as in vitro. However, there is reason to believe that intralesional laser fiber treatment of HS tunnels may provide a new tissue-sparing alternative to conventional surgical techniques with a potential to produce fewer side effects, less scaring, shorter downtime after surgery and possibly, also improved inflammatory control.

This study aims to investigate the efficacy and safety of 1470 nm laser fiber treatment of HS tunnels and add new knowledge of the microbiota as well as of laser-tissue interactions by in vivo ultrasound and in vitro histology.

Methods:

Study execution:

The project will be carried out at the Dermatological Department, Roskilde University Hospital under the leadership of principal investigator Professor Gregor Jemec, MD, DMSc. Senior doctor Ditte Marie Lindhardt Saunte, MD, PhD and Medical Doctor Elisabeth Hjardem Taudorf MD, PhD will run the project in cooperation with the established research group at the department

Study design:

A prospective cohort study of intralesional laser fiber treatment of HS fistulas is planned. Demographic data and information regarding prior treatments for HS will be collected in standardized case-report forms.

After signing informed consent, patients with HS tunnels in typical areas will be enrolled. Patients who have at least two suitable tunnels in typical HS areas will be invited to participate in the randomised within-person design to receive experimental laser fibre treatment. Two comparable HS tunnels from each patient will be selected enabling a subsequent randomisation to receive treatment or to serve as an intra-individual control, respectively.

Intervention:

The experimental treatment consists of one session of thermal coagulation with intralesional 1470 nm diode laser fibre in the entire length of one HS tunnel after injection of local anaesthetics (Mepivacaine-adrenaline). Both ends of tunnels selected for laser treatment must be accessible from the skin surface to ensure treatment of the entire tunnel.