How do you treat adrenal metastases with SBRT?

Adrenal glands move quite a bit with breathing. I would strongly recommend some form of motion management, either with breath hold, or 4DCT with abdominal compression, (the latter of which is my personal preference).

I draw GTV (just tumor, not entire adrenal gland) as defined on whatever imaging showed you the cancer, be that a CT with contrast or a PET/CT (have not had an MRI diagnosed adrenal tumor as of yet).

I then create an ITV on a 4DCT. I do slice by slice evaluation on a 4DCT rather than a MIP as there is no air to help differentiate. I do a PTV off of that, generally 5 mm in all directions. Similar to other SBRT cases, no CTV to account for microscopic disease.

Adrenal cases can be very tricky based on proximity of the small intes...

Whole gland SBRT with a PTV margin on GTV (we use 5 mm), supine with motion management (LINAC with 4DCT), fuse PET/CT or MRI for tumor delineation, no fiducial markers. In our experience, 36 Gy in 3 fractions works well (Reshko et al., PMID 34277086). Here is a great meta-analysis that shows improved local control with higher BED: Chen et al., PMID 32001383.