My 71 year old wife was diagnosed with GBM grade 4 June 2023. She did surgery, 30 radiations and 42 days chemo. She is not getting ready for cycle 3 chemo. Today we went to the library and she checked out several books, which she reads, not as voraciously as before. We went on a walk of 3/4 mile. We can still carry on a conversation. She had covid last week and made it through it ok, even with an impaired immune system. We have been to ER twice and hospitalization for 3 days in the last several months. There have been a number of daily challenges such as weight loss, and regulating daily bowels. However, MRI's have shown no tumor regrowth the past two cycles .
You asked is it worth it for a 70 year old to undertake this process. In the case of my wife and I, we have to say absolutely yes. You mention your friend has limited mobility. Do doctors say there is a chance of this correcting? Even if that is not the case, can the patient enjoy being with others, and converse? Does he have a willingness to go through the process, because it takes a strong will. I don't think there is a blanket answer to your question as each situation is uniquely different.
Dan