my non-medical opinion and intuition is to tell you no food for a few weeks and I feel a strong chance his body will consume the tumor.
he is 65 and may life a long time so worth a try?
i doubt he is so low in body fat that he cannot handle no fat or carb energy for a few weeks, a couple at least. after maybe a day or two after starting fasting the body uses up all the carb stores in the liver and muscles and then starts to consume only body fat and negative cells. there are also amazing accounts of people's scaring healing, other ailments healing, etc.
in addition to the electrolytes they can also give him vitamins and minerals in supplement form. the longest ever recorded fast was over a year for an obese man and he did it with medical supervision with supplements given by his doctors.
when i was having a headache several months ago i laid in bed and listened to this track https://www.youtube.com/watch?v=MV8_rpKjZvo
for maybe a minute and it went away with focus on my blood and blood cells to pump to the issue and heal.
given my experience and all the research i have done i think after everyone becomes a full grown adult by the age of maybe 18 or 20 they should do at least a few days of no eating every year and maybe one longer fast of a week or two when possible just as a preventative measure and for clearer thinking.
i am telling you. when you see what comes out of your body after a week with no food you know you did the right thing. gross i know.. it also gives you clearer thinking as well. many benefits in addition to excess weight loss. i am not saying it is easy at first. try going one day yourself with no food. but you get used to it.
I am sending good intent. I command the heart and arteries to pump much blood to the issue and the blood cells to heal and destroy negative cells and eliminate them from the body.
its nice to know the truth though..
good luck to him.