Microwave Ablation in Mild Axillary Hidradenitis Suppurativa

Hidradenitis suppurativa (HS) is a chronic, inflammatory skin disease of the hair follicle, and is predominantly located in the axillary, inguinal and anogenital regions. Current treatment options for HS include systemic oral antibiotics, anti-TNFα, and surgery, which are used to treat the consequences rather than treating the primary pathogenesis of HS. With microwave ablation (MWA), using the heat generated from electromagnetic waves in the microwave energy spectrum, hair follicles, eccrine and apocrine glands in the (hypo)dermis are ablated through thermolysis. MWA was recently approved for the treatment of axillary hyperhidrosis (miraDry) and removal of axillary hair (miraSmooth). By permanent removal of hairs and sweat glands, the investigators hypothesize a beneficial and long-term sustainable preventive effect of MWA in HS patients.

• Microwave ablation (Device): A one-sided (either right or left axillary area) single MWA treatment using a miraDry system. The miraDry device has a microwave output frequency of 5.8 GHz and microwave energy level settings ranging from 1 to 5, corresponding with a delivery time in seconds between 2.40 sec and 3.00 sec. For this study standard 5 (i.e. 3.00 sec) is set as treatment setting.

Primary outcomes

• Hidradenitis Suppurativa Clinical Response (HiSCR50) [6 months]: The proposed definition of 50% responders to treatment (HiSCR50 achievers) is: (i) at least a 50% reduction in ANs, (ii) no increase in the number of abscesses, and (iii) no increase in the number of draining fistulas from baseline

Secondary outcomes

• Hidradenitis Suppurativa Clinical Response (HiSCR30) [6 months]: The proposed definition of 30% responders to treatment (HiSCR30 achievers) is: (i) at least a 30% reduction in ANs, (ii) no increase in the number of abscesses, and (iii) no increase in the number of draining fistulas from baseline
• Patient-reported number of HS flares [6 months]: The number of HS flares in the treated and untreated axillae. At baseline retrospective assessment on last month, and during follow-up prospective assessment using a diary where patients will report the number of acute boils per axilla.
• Average number of hair containing follicles [6 months]: Dermatoscopy of three fields per axilla
• Extent of sweat production [6 months]: Starch-Iodine test per axillary region
• Patient-reported pain and pruritus [6 months]: Numerical rating scale (NRS) to assess pain and itch per axillary region
• Incidence of (treatment-emergent) adverse events [6 months]: Safety and tolerability of the treatment

Sex: All, ages: 18 Years to 80 Years

Inclusion Criteria:

* Adult (≥ 18 years of age) male or female patients with mild HS and able to participate, willing to give written informed consent and to comply with the study restrictions;
* Minimum of 3 AN-count located in each axilla;
* Maximum of 5 AN-count located in each axilla.

Exclusion Criteria:

* Patients with >1 abscesses or draining fistulas per axillary region;
* AN-count ≥ 5 in other regions than the axillary area;
* Any current and / or recurrent clinically significant skin condition in the treatment area other than HS;
* Surgical scars covering more than 25% of each individual axillary area;
* Open surgical wound(s) in the axillary areas prior to randomization;
* Use of anti-inflammatory or immunomodulatory medication (intralesional corticosteroids, oral antibiotics, biologics, prednisone) within 2 weeks prior to randomization;
* Contraindication for miraDry therapy;
* Heart pacemakers and other electronic device implants;
* Supplemental oxygen;
* Resistance to or history of intolerance of local anesthesia including lidocaine and epinephrine;
* Previous use of miraDry therapy or MWA in the axillary area;
* Previous use of successful laser or light therapy for hair removal in the axillary area;
* Use of botulinum toxin injections 6 months prior to randomization;
* Use of aluminiumhydroxychloride 1 month prior to randomization;
* Pregnant or lactating women at randomization.

• Errol Prens, MD, PhD, Principal investigator, Professor