Hope your Dad is doing well.
I am a Nuclear Medicine Physician. In case of relapsed disease of Non-Hodgkin Lymphoma
after second and third line chemotherapies, there is still an option of a radionuclide
, or Zevalin). Both modalities show upto 60% overall response and prolong the survival. The side effects are less compared to conventional chemotherapies.
Contact your oncologist
or me for further details.
Hope this could be of help
Regards and best wishes