This is a rare and challenging case (though I’ve actually seen this exact scenario a few times). I don’t think there’s a great answer, unfortunately. Re-irradiation with protons may be the best choice. Depending on the sarcoma histologic subtype, I would suggest clinical trial and/...

As often, the devil is in the details -- histology of current sarcoma, time from and the dose of prior RT, prior tx for this diagnosis, etc -- but in general I agree with @Anusha Kalbasi. Any reasonable chance of long-term control for unresected sarcoma requires dose escalation (Kepka et al., PMID 1...