What is your preferred regimen for palliative treatment of unresectable retroperitoneal sarcoma?

First, I’d distinguish:

1) If the goals are PURELY palliative, can pick a conventional (30/10) or more adventurous (39/13, QuadShot, etc) palliative regimen - there is a separate MedNet thread on dose/fractionation for sarcoma palliation. But efficacy and durability are likely limited.

2) If the primary RP disease is likely to be life-limiting (which can be true even in some patients with metastatic disease), it is worthwhile being more aggressive. I've used a 15 fx regimen with reasonable success. High 30s to 45 Gy to PTV, GTV/ITV to 45 to low 50s, and a contraction off of GTV/away from OARs to as hot as feasible, usually mid 50s to 60. Undercover target volumes as needed to meet OAR metrics. While doing that, get as much of tumor as you c...