Immunotherapy is the use of medicines to help a person’s own immune system to recognize and destroy cancer cells more effectively.  An important part of the immune system is its ability to keep itself from attacking normal cells in the body. To do this, it uses “checkpoint” proteins on immune cells, which act like switches that need to be turned on (or off) to start an immune response. Cancer cells sometimes use these checkpoints to avoid being attacked by the immune system.

Drugs that target these checkpoints (called checkpoint inhibitors) can be used to treat some people with non-small cell lung cancer (NSCLC).  Cancer.org

Dad will be receiving durvalumab (generic name - imfinzin) every two weeks for the next year.  It will be administered through an IV at the cancer center right in Robbinsdale.  He still has a port in his chest, so it is a pretty low key appointment for him.  He may administer fatigue, but it won't be anything as severe as the radiation / chemo side effects.  
More on durvalumab here and here.