What are reasonable SBRT dose constraints for the lumbosacral plexus?

There are published dose tolerance guidelines for the sacral plexus with the AAPM TG101 report Benedict et al. Med. Phys 37(8): 4078-4101, 2010. Realize these have not been validated

On page 4086, there is a table with suggested dose constraints for a 3 fraction regimen that include a threshold dose ...

Not a direct answer but I would note that without concurrent chemotherapy or prior RT, the tolerance of sacral plexus to conventionally fractionated RT appears quite high, with plexopathy appearing only >77 Gy. This is roughly comparable to conventional H&N brachial plexus constraints (which are des...

Using TG101 or RTOG constraints, I have not seen plexopathies or neuropathies if radiation naive.

We have published the Indiana University experience of SBRT for apical tumors (led by @Dr. First Last who was an IU resident at that time) in Green Journal. Dosimetric correlation with brachial plexopathy was performed and the cut-off was 26 Gy in 3-4 (mostly 3) fractions. This kind of corroborated ...