My care is from Memorial Sloan Kettering.
My oncologist advised taking a centrum silver type vitamin, and skipping supplements in favor of good nutrition.
The only additive or supplement my oncologist said NOT to take was turmeric. While it shows some cancer preventative properties, there may be an issue with it actually interfering with treatment. It's ok to use a little as a spice, in cooking, but not as a supplement. More research needs to be done.
Our diet was not bad, but we did improve it.
By our own decision, we decided to eat as organically as possible. The nutrition is not different, but there are some pesticides, fungicides, and processing agents in food that I'd be better off without.
We are 80% vegetarian, with mostly lean chicken or fish, in small amounts, on the other days.
We eat whole grains/seeds every day: barley, oats, quinoa, chia, flax, brown rice, etc.
we eat beans 4/5 times a week
We bought a vitamix and have a smoothie a day, with homemade organic fat free plain yogurt, fruit, flax or chia, etc.
No white sugar. I use raw organic honey, raw cane sugar, maple syrup, or agave.
Red meat only once a month or so, sometimes less.
Cruciferous veggies almost every day . Broccoli, cauliflower, cabbage, as well as the leafy deep greens.
No store bought bread products. I make all our breads with organic whole flours. I make sourdough english muffins, bread, pizza, etc. but we don't eat many bread products.
A square of dark chocolate a day!
That may sound weird or boring to you, or expensive, but I can tell you my food bill went down, I'm cooking really delicious interesting things, and we've each lost 22 lbs in the last 3.5 months. Overall our meals look pretty normal, you would not sit down at my table and think, gee these people eat weird stuff.
My diet (above) is layered over Weight Watchers so it incorporates all their Good Health Guidelines.
Good luck in your recovery! Stay strong!