3553 - Low Dose Radiotherapy in Treatment of Recalcitrant Hidradenitis Suppurativa

Purpose/Objective(s):

Hidradenitis suppurativa (HS) is a benign, chronic inflammatory condition that results in painful lesions that can progress to abscesses, skin tunnels and fibrotic scars. Dissecting cellulitis (DC) of the scalp is a condition with similar pathophysiology but occurs in a different location. Initial management involves escalating interventions of antibiotics, biological agents, and surgical interventions, but these generally only result in modest symptom improvement. Radiotherapy is infrequently used for these conditions. This study aimed to determine the effectiveness of external beam radiation as an adjunct treatment strategy for refractory HS and DC.

Materials/Methods:

Patients with HS or DC who were treated with radiotherapy at a single institution from 2022 to 2024 were retrospectively identified. Patients were treated with either 750cGy in 3 or 1500cGy in 6 fractions for DC. Treatment modalities included enface electrons, 3D conformal, or volumetric modulated arc therapy. Retreatment with 750cGy in 3 fractions was offered for recurrent or recalcitrant disease. Patient demographics (age, race, sex, BMI) were recorded. Primary endpoint of treatment response was characterized based on available clinic notes and clinical imaging documentation provided by the treating radiation oncologist and dermatologist.

Results:

Seven patients with HS and one patient with DC who were treated to 25 sites were identified in this retrospective analysis. The median age was 39.5 years (range 33-59); four patients were Black and four were White. The median follow-up was 1.06 years, and the median BMI was 32.98 (range 28.13-45.73). Treated HS locations included six right groin, six left groin, four buttock, three left axilla, two right axilla, two perineum/scrotum, one scalp, and one low abdomen. The Hurley stage was 3 in 22 cases (88%, range 2-3), and the median pretreatment pain score was 5.5 (range 0-10). The median number of pre-radiation interventions was 7.5 (range 3 - 17). In all patients, previous treatment included courses of antibiotics (4.5, range 1-12) and immunosuppressive agents (1.5, range 0-3). Six patients had been treated with a biologic agent, two patients had been previously treated with retinoids, and two with deroofing. Two cases (five sites) were retreated for persistent disease 12 months after initial treatment of which two sites did not respond to repeat treatment. No grade 2+ acute or late adverse events from radiotherapy occurred. 4/25 (16%) lesions had a complete response, 15/25 (60%) had a partial response, 6/25 (24%) had no response. For those with a pain score prior to treatment, 75% had a reduction in pain score during the first radiotherapy follow-up.

Conclusion:

In this heavily pretreated retrospective cohort, low doses of radiotherapy demonstrated high response rates with 19/25 of treated lesions demonstrating a reduction in lesion appearance, pain, flair-ups, and/or drainage. Prospective studies exploring the use of radiotherapy for HS are warranted.