Background
Preliminary consensus guidelines from an international expert panel for preoperative RT in retroperitoneal sarcoma (RPS). RPS poses unique RT planning challenges: large tumors, proximity to bowel/kidney/liver/spinal cord, and high local recurrence (>50%) driving disease-specific mortality. Panel drawn from major sarcoma centers across North America, Europe, and Australia.
Interventions and follow up
Treatment: Expert consensus on RT approach (not a clinical trial)
Primary endpoint: Consensus recommendations
mFollow up: N/A
Primary endpoint: Consensus recommendations
mFollow up: N/A
Results
Pre-op dose: 50.4 Gy in 28 fractions (standard); IMRT/VMAT recommended for dose sculpting
Boost dose: Additional 5.4 Gy to high-risk margins (abutting vessels/organs) in selective cases
Bowel constraint: V45 <195 cc (small bowel); strict avoidance of dose escalation near bowel
Indications: All resectable primary RPS, especially liposarcoma and leiomyosarcoma histologies
Boost dose: Additional 5.4 Gy to high-risk margins (abutting vessels/organs) in selective cases
Bowel constraint: V45 <195 cc (small bowel); strict avoidance of dose escalation near bowel
Indications: All resectable primary RPS, especially liposarcoma and leiomyosarcoma histologies
Adverse events
Small bowel: Nausea, diarrhea
Kidney: Aim to spare contralateral kidney
Liver: V30 <30% for right-sided tumors
Spinal cord: Maximum dose <45 Gy
Post-op RT: Higher toxicity due to bowel adherence to tumor bed
Kidney: Aim to spare contralateral kidney
Liver: V30 <30% for right-sided tumors
Spinal cord: Maximum dose <45 Gy
Post-op RT: Higher toxicity due to bowel adherence to tumor bed
Conclusions
International consensus supports pre-op RT for resectable RPS, using IMRT to achieve 50.4 Gy with strict bowel constraints. This provides better bowel displacement than post-op RT and lower total dose, while enabling dose escalation to high-risk margins away from bowel.
Key Limitations
Consensus-based prior to prospective RCT validation; STRASS trial (pre-op RT vs no RT) was ongoing at time of publication; dose recommendations vary by institutional experience; smaller RPS centers may lack technical expertise for complex IMRT planning adjacent to bowel.
Clinical Context
The STRASS trial (Bonvalot, Lancet Oncol 2020) subsequently showed no DFS benefit for pre-op RT in RPS overall, though a histology-specific benefit was suggested for well-differentiated/dedifferentiated liposarcoma. These consensus guidelines remain relevant for institutional planning; pre-op RT is still offered selectively based on histology and multidisciplinary discussion at major sarcoma centers. Pre-op RT preferred over post-op RT for RPS (better bowel displacement, lower dose 50.4 Gy vs 60-66 Gy); CTV = GTV + 1.5-2 cm margins, reduced posteriorly at bony structures, with bowel as primary dose-limiting structure.