Adjuvant Radiotherapy for Soft Tissue Sarcoma

Soft tissueAdjuvant

Adjuvant Radiotherapy for Soft Tissue Sarcoma

Soft tissue sarcoma of the extremity, trunk, and head and neck - intermediate and high grade, post-resection

Overview

  • Adjuvant (post-operative) radiotherapy delivered after surgical resection of soft tissue sarcoma
  • Aims: eradicate microscopic residual disease, improve local control, reduce local recurrence rate
  • Landmark trial: Rosenberg et al. (NCI) demonstrated limb salvage + RT equivalent to amputation in extremity STS
  • Yang et al. RCT confirmed adjuvant RT reduces local recurrence in high-grade extremity STS (1% vs 22% recurrence at 10 years)
  • Standard of care for high-grade STS after limb-sparing surgery, particularly with close or positive margins
  • Lower wound complication rate than neoadjuvant RT but higher late toxicity (fibrosis, oedema)

Regimen & Dosing

Regimen

  • External beam radiotherapy to the surgical bed and tumour site
  • Total dose: 60 Gy (negative margins) to 66 Gy (positive/close margins) in 2 Gy fractions
  • IMRT or VMAT preferred to minimise dose to surrounding normal tissues
  • Brachytherapy: alternative or adjunct, particularly for smaller tumours - delivered via catheters placed intraoperatively
  • Treatment commences after wound healing - typically 4–6 weeks post-surgery

Dosing

  • 60 Gy in 30 fractions (R0 negative margins) - standard adjuvant dose
  • 66 Gy in 33 fractions (R1 positive margins or close margins <1 mm)
  • Boost may be given to area of closest/positive margin: 10–16 Gy additional in selected cases
  • CTV: surgical bed including drain sites and biopsy scar, with 2–4 cm longitudinal margin and 1.5–2 cm radial margin
  • PTV: CTV + 0.5–1 cm setup margin
  • IMRT/VMAT dose constraints: spare uninvolved circumferential skin, protect joint surfaces, limit bone dose

Eligibility & Contraindications

Eligibility

  • Histologically confirmed intermediate or high grade soft tissue sarcoma
  • Limb-sparing resection performed (wide resection with marginal or positive margins)
  • Low-grade STS: adjuvant RT considered on case-by-case basis (especially if positive margins or proximity to critical structures)
  • Benign/atypical lipomatous tumours: adjuvant RT not routinely indicated
  • ECOG performance status 0–2
  • Adequate wound healing before commencing RT (minimum 3–4 weeks post-surgery)

Contraindications

  • Previously irradiated field (risk of radionecrosis - relative contraindication, discuss at MDT)
  • Active wound infection or breakdown (delay RT until wound healed)
  • Pregnancy
  • Widespread metastatic disease where local control unlikely to benefit patient
  • Gardner syndrome/desmoid association: avoid RT due to risk of triggering new desmoid tumours

Monitoring

  • Weekly on-treatment review: acute skin reaction (erythema, moist desquamation), oedema
  • Late toxicity monitoring at each follow-up visit: fibrosis, lymphoedema, joint stiffness, secondary fracture
  • Bone density assessment if large bone included in field (stress fracture risk)
  • Limb volume measurements for lymphoedema surveillance
  • MRI of primary site for local recurrence surveillance (see follow-up guidelines)
  • Physiotherapy referral for all patients to manage fibrosis and joint stiffness

Notes

  • Adjuvant RT reduces local recurrence but does not improve overall survival in most studies
  • High-grade tumours >5 cm with negative margins: adjuvant RT strongly recommended
  • Low-grade tumours with wide negative margins: adjuvant RT may be omitted at specialist MDT discussion
  • Radiation-induced sarcoma: rare late complication (~0.1%), typically osteosarcoma or MFH/UPS, arising years after RT - must be distinguished from local recurrence
  • Avoid radiotherapy for desmoid-type fibromatosis where surgical excision is feasible (may trigger new desmoids in FAP)
  • Brachytherapy (low-dose or high-dose rate): alternative to EBRT, particularly in anatomically challenging sites
  • Perioperative brachytherapy: catheters placed at surgery, loaded post-operatively
  • Proton beam therapy: emerging role for paediatric STS and anatomically constrained tumours

Medical disclaimer

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