How do you approach repeat SBRT in the abdomen, specifically when considering constraints for bowel and mesenteric vessels?

Great question with no clear guidelines. If it was the same lesion of prior RT, I would consider other liver-directed therapies as I would worry about the ability to get in meaningful dose. If it was a different lesion, I would create a cumulative plan and try to minimize bowel dose aggressively. If concerned about bowel overlap, in the setting of reirradiation, I would consider a more hypofractionated RT schedule of 15 fractions. I don't generally constrain mesenteric vessels, even in the setti...

I generally agree with Drs. @Dr. First Last and @Dr. First Last. I do not constrain the dose to mesenteric vessels. The dose is limited by the luminal GI structures such that the vessels should not be at risk.

In the case of a patient who was treated over a year ago, we would typically create a plan sum discounting the prior dose by 50%, as described in Price Jr. et al., PMID 33490729. I would also agree that the decision of whether or not to treat would be related to the clinical context - is th...

Perhaps a little bit more information would be helpful. What was previously treated - liver? Or mesenteric metastatic node? Or PA/RP node? For liver, 30/5 seems low.

If it was mesenteric mass/node repeating radiation to the same lesion may not be beneficial, in my opinion. The dose you would be able to deliver due to adjacent luminal structures may be of limited value to provide control (unless the re-irradiation goal is palliative).

To address the question re vessel constraints, we do not have ...