What proton dose regimen would you use for locally recurrent esophageal cancer previously treated with chemoRT?

Like @Dr. First Last, I would also somewhat challenge the premise of the question. Typically, the dose-limiting structure for re-irradiating esophageal cancer is the esophagus itself, so protons do not offer an inherent advantage in this case. Protons may still be reasonable to reduce lung or heart dose, but the heart of the question is really: what cumulative dose is safe to deliver to the esophagus? The tradeoff here is between disease control on the one hand and fistula on the other hand, and...

There are several varying clinical scenarios that this question can represent, including:

1) A recurrence after trimodality therapy, with gross disease present a significant distance from the surgical anastomosis, in tissue that was previously unirradiated.

2) A recurrence after trimodality therapy with the recurrence in close proximity to the surgical anastomosis and prior radiation field.

3) A recurrence after bimodality (chemo and radiation) therapy, directly in the prior radiation field.

After a...

Palliatively. Not a good use of protons.

For patients who are not operative candidates, who relapse after chemo-RT, at our center, we have re-treated with 45 Gy chemo-RT using pencil-beam scanning proton therapy and CBCT guidance. The margins are pretty narrow, no elective nodal coverage, and typically follows a prior dose of 50.4 Gy with a gap of 6 to 12+ months between the prior course to allow some repair.