Soft tissueNeoadjuvant

Neoadjuvant Radiotherapy for Soft Tissue Sarcoma

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

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

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

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

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)

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

Protocols/Treatment Protocols/Neoadjuvant Radiotherapy for Soft Tissue Sarcoma