Hi the Cancer Council has a booklet ( available on their website) called “ food and nutrition” that is good.
I saw a nutritionist at the Kinghorn cancer centre in Sydney after meeting radiotherapy finished and she pretty much told me all the stuff I had already implemented from reading that publication.
Give up or drastically reduce alcohol, get rid of sugary drinks and replace processed foods ( including sugary processed foods) with fresh fruit and vegetables , eat regular meals with all the recommended food groups and have enough fish and lean protein.
That doesn’t mean you can never have a treat , just be mindful of what goes in your mouth.
I kept a food and drink diary for the first few weeks and also a set of scales I get on every morning.
I lost 10 kilos and am how back to my marriage weight from 30 years ago.
I also am still seeing an exercise physiologist at the same centre as the diet and exercise go hand in hand.
I am 62 so it’s never too late to start!