What RT fields would you recommend for a patient with early-stage diffuse large B-cell lymphoma who refuses or is unfit for systemic therapy?

For a patient with stage I DLBCL, RT fields should encompass the involved site with a generous margin, the latter not precisely defined but dependent on what the site is and what side effects need to be considered with larger volumes. RT fields should not change much if the patient is not receiving ...

If no chemotherapy at all, I would consider involved-field radiation (IFRT), at least for the initial dose. For aggressive lymphoma, I feel it is safer to cover the entire lymphatic region. This is probably similar to the answers given by Dr. @Dr. First Last and Dr. @Dr. First Last.