Neoadjuvant Radiotherapy for Soft Tissue Sarcoma

Soft tissueNeoadjuvant

Neoadjuvant Radiotherapy for Soft Tissue Sarcoma

Soft tissue sarcoma of the extremity, trunk, and retroperitoneum - intermediate and high grade

Overview

  • Neoadjuvant (pre-operative) radiotherapy is delivered before surgical resection
  • Aims: tumour downsizing to facilitate resection, sterilise surgical margins, treat microscopic satellite lesions
  • Canadian randomised trial (O'Sullivan et al.) demonstrated neoadjuvant RT equivalent to adjuvant RT in local control but with lower late toxicity
  • Preferred approach for extremity STS at many centres due to reduced late fibrosis and improved functional outcomes compared to adjuvant RT
  • Total dose lower than adjuvant RT (50 Gy vs 60–66 Gy) - smaller treatment volume pre-operatively (no surgical bed)
  • Wound complication rate higher with neoadjuvant RT (approximately 35%) compared to adjuvant RT

Regimen & Dosing

Regimen

  • External beam radiotherapy (EBRT) to the primary tumour with appropriate margin
  • Total dose: 50 Gy in 25 fractions (2 Gy per fraction, 5 days per week) - standard
  • Intensity-modulated radiotherapy (IMRT) or volumetric modulated arc therapy (VMAT) preferred to minimise dose to critical structures
  • Surgery typically performed 4–6 weeks after completion of neoadjuvant RT (allows acute wound healing)
  • Intraoperative radiotherapy (IORT) may be used as boost at selected centres

Dosing

  • 50 Gy in 25 fractions over 5 weeks (2 Gy/fraction)
  • Consider 3D conformal or IMRT/VMAT planning to minimise dose to joint, bone, and skin
  • Clinical target volume (CTV): GTV + 1.5–2.5 cm longitudinal margin + 1–1.5 cm radial margin (adapted to anatomical barriers)
  • Planning target volume (PTV): CTV + 0.5–1 cm institutional setup margin
  • Dose constraints: limit circumferential skin dose, preserve uninvolved bone cortex, avoid joint irradiation where possible

Eligibility & Contraindications

Eligibility

  • Intermediate or high grade soft tissue sarcoma of extremity or trunk
  • Tumour amenable to surgery after neoadjuvant RT (borderline resectable or planned wide resection)
  • Retroperitoneal STS: neoadjuvant RT being evaluated - STRASS trial results pending wider adoption
  • ECOG performance status 0–2
  • No prior radiotherapy to the same field
  • Adequate skin integrity over planned treatment field

Contraindications

  • Previously irradiated field (risk of radionecrosis)
  • Skin ulceration or active infection over treatment field
  • Pregnancy
  • Tumour abutting critical structures receiving high dose (major vessels, spinal cord) - plan carefully
  • Patient unable to maintain positioning for treatment delivery

Monitoring

  • Weekly on-treatment review: skin reaction, oedema assessment, pain
  • Wound assessment at 4–6 weeks post-RT (prior to surgery)
  • Surgical wound monitoring post-operatively: higher wound complication rate after neoadjuvant RT
  • Late toxicity: fibrosis, joint stiffness, lymphoedema - assess at each follow-up
  • Pathological response assessment at surgical resection (% necrosis)

Notes

  • Wound complication rate approximately 35% with neoadjuvant RT vs ~17% adjuvant RT - patients must be counselled
  • Lower late toxicity (fibrosis, oedema, joint stiffness) compared to adjuvant RT - important for functional outcomes
  • Treatment volume is smaller pre-operatively (tumour only, not surgical bed) - allows dose reduction to normal tissues
  • Myxoid liposarcoma is highly radiosensitive - neoadjuvant RT produces excellent histological response at lower doses (36 Gy)
  • Re-excision after unplanned excision ('whoops' surgery): RT field must include biopsy scar and surgical tracks
  • Proton beam therapy: emerging role to reduce dose to critical structures - available at specialist centres
  • Multidisciplinary planning (surgeon + radiation oncologist) essential before commencing RT

Medical disclaimer

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