# HDR Brachytherapy in the Treatment of Skin Kaposi Sarcoma: A Mono-Institutional Series

## TL;DR

This study shows high-dose-rate brachytherapy is a safe and effective treatment for skin Kaposi sarcoma with excellent long-term results.

## Contribution

The study provides long-term evidence supporting the use of hypofractionated contact HDR brachytherapy for Kaposi sarcoma treatment.

## Key findings

- 100% local control, overall survival, and disease-specific survival at 2 years.
- 62.5% of lesions achieved complete response with minimal toxicity.
- Treatment compliance improved due to short hypofractionated schedules.

## Abstract

Kaposi sarcoma is highly radiosensitive, yet evidence on high-dose-rate contact brachytherapy (c-HDR-BRT) remains limited. In a retrospective series of 10 patients (40 lesions) treated with Leipzig applicators at our institution between 2010 and 2023, hypofractionated schedules of 10–30 Gy (1–3 fractions) achieved favorable long-term local outcomes. At a median follow-up of 10.3 years, 2-year local control, overall survival, and disease-specific survival were 100%. Complete response was observed in 62.5% of lesions, and partial response was observed in 37.5%. Treatment was well tolerated, with mostly grade 1–2 acute skin reactions and only one grade 3 event. The short treatment courses improved compliance, particularly for patients with multiple lesions. These findings support c-HDR-BRT as a feasible and well tolerated local treatment option for Kaposi sarcoma and justify further prospective evaluation.

Background: Kaposi sarcoma (KS) is a multifocal, angioproliferative neoplasm strongly associated with human herpesvirus-8 infection. Radiotherapy(RT) is a well established treatment due to the intrinsic radiosensitivity of KS lesions. High-dose-rate contact brachytherapy allows precise dose delivery with optimal sparing of surrounding tissues; however, its application in KS remains poorly documented. Methods: We conducted a retrospective analysis of 10 patients with histologically confirmed KS treated with c-HDR-BRT between June 2010 and June 2023. A total of 40 cutaneous lesions were treated using Leipzig applicators with hypofractionated regimens: 10 Gy in 1 fraction, 20 Gy in 2 fractions, or 30 Gy in 3 fractions. Treatment parameters were individualized based on lesion size and location. Local control (LC), overall survival (OS), disease-specific survival (DSS), and toxicity (graded by the RTOG criteria) were evaluated. Follow-up assessments were performed every four months during the first year and annually thereafter. Results: At a median follow-up of 10.3 years, the 2-year LC, OS, and DSS rates were 100%. Complete response was achieved in 62.5% of lesions, with a partial response observed in 37.5%. Grade 1–2 acute skin toxicities were recorded in 55% of treated lesions, while grade 3 toxicity occurred in a single case (2.5%) and was managed conservatively. The hypofractionated schedule significantly improved patient compliance, particularly in those with multiple lesions requiring sequential irradiation. Conclusions: Our long-term institutional experience supports c-HDR-BRT as a feasible and well tolerated local treatment option for the management of KS, providing favorable long-term local outcomes. These results support the inclusion of c-HDR-BRT in the multidisciplinary treatment of KS, warranting further prospective evaluation.