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

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

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

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

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

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

Protocols/Treatment Protocols/Adjuvant Radiotherapy for Soft Tissue Sarcoma