How would you treat a stage IE diffuse large B-cell lymphoma of the adrenal gland in an elderly patient who is not a candidate for systemic therapy?  

This is an extremely tough situation if the patient cannot get systemic therapy. These tend to be non-GCB subtype with a generally poor prognosis even with R-CHOP based chemotherapy regimen with high rates of systemic and CNS relapses. Typically, I would recommend R-da-EPOCH,  CNS directed chem...

If chemotherapy is not an option, my thinking would be to treat with EQD2 of 40-50 Gy. While virtually no data, I would have no difficulty treating with a more accelerated fraction if IMRT or tight 3D volume possible or SBRT as mentioned by Dr. @Joseph K. Chiu.