34. Uncommon indications for brachytherapy - The GEC-ESTRO Handbook of Brachytherapy

Uncommon indications for brachytherapy

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THE GEC ESTRO HANDBOOK OF BRACHYTHERAPY | Part II Clinical Practice Version 1 - 30/04/2025

34.1 Soft tissue sarcomas of the extremities and superficial trunk in adults Rafael Martínez-Monge, Santiago Martín Pastor, Luis I. Ramos, Benigno Barbés, Mikel San-Julián, Jorge Gómez Alvarez

1. Introduction

3 3 3 4

5. Dose

4 4 5 9

2. Clinical Indications

6. Results and adverse side effects

3. Tumour and Target Volume

7. References

4. Technique

1. INTRODUCTION

2. CLINICAL INDICATIONS

Soft tissue sarcomas of the extremities and the superficial trunk are a rare (<1% of all adult tumours) and heterogeneous group of solid tumours of mesenchymal origin (more than 50 different histologic subtypes) and represent the majority of all soft tissue sarcomas [1]. Localized tumours are treated primarily with surgery and irradiation. The use of adjuvant chemotherapy in this setting is not a standard treatment. It can, however, be proposed for fit patients affected by disease at high risk of metastases [2]. Most soft tissue sarcomas share common diagnostic and treatment pathways. However, a few subtypes (e.g. rhabdomyosarcoma, desmoid tumours,) are treated according to disease-specific algorithms. Most soft tissue sarcomas are sporadic. A minority can be related to certain predisposing factors such as prior radiation therapy to the affected area, chronic lymphoedema, chemicals and genetic syndromes (e.g. Li-Fraumeni syndrome, neurofibromatosis, etc.) [3]. Amputation has long been abandoned as the standard treatment for soft tissue sarcomas since similar oncological outcomes are obtained with functional surgery and adjuvant irradiation [4]. Both adjuvant low-dose rate (LDR) brachytherapy and external beam irradiation (EBRT) have resulted in improved local control rates compared with surgery alone in two different phase III trials [5,6]. However, the timing of surgery and irradiation (i.e, preoperative vs. postoperative) does not seem to impact on local control rates or survival [7] although preoperative irradiation has been related to a higher wound dehiscence rate [7] and postoperative irradiation to greater fibrosis, joint stiffness and bone damage [8]. Current international guidelines [1] support the use of LDR (or high-dose rate (HDR) equivalent) brachytherapy alone in margin negative tumours that meet the criteria for adjuvant irradiation or LDR (or HDR equivalent) brachytherapy combined with EBRT for margin positive patients.

Brachytherapy can be used in the majority of patients with soft tissue sarcomas that require adjuvant irradiation and are technically implantable. Brachytherapy may be advantageous to external beam irradiation in specific anatomical locations or in children where the irradiated volume has to be restricted Tumour scenarios In general, surgery alone may be adequate for small (<5 cm) low grade tumours with clear surgical margins (>1 cm). There are nomograms available to assess the risk of recurrence with surgery alone in individual patients [10]. In practice, most patients with AJCC 8th edition stage Ib, II and III tumours and patients with unirradiated locally recurrent tumours are candidates for adjuvant irradiation [1] and therefore, brachytherapy can be used in these patients as the sole treatment modality or combined with EBRT. Anatomical scenarios Most tumour locations are suitable for brachytherapy as long as the implant is at least >5mm under the skin surface and target coverage is guaranteed. The presence in the surgical bed of dose limiting structures such as neurovascular bundle, bone, etc. is not a contraindication for brachytherapy [11]. In fact, tumours adjacent to these organs are at greatest risk of local failure due to the inability to obtain wide tumour-free margins and the benefit of brachytherapy for dose escalation in the presence of inadequate margins is maximal [12]. In these situations, special care must be paid to technical details to avoid organ at risk damage (see section 4 : Technique).