Chemo

After first chemo and radiation the cancer has srank and doctor was going to remove stomach but at the operation he has found that cancer is olso oround main vain so he could not operate.After the recovery second chemo will start.Is there any one that went similar path.Did the Oncologist recomended to take vitamins or other means to bild the immune system.Some oncologist recomend to bild the immune system some say do not take anything.Please let me know what was your experience in this case.Is there any one that had cancer oround main vain and chemo did help to srink the tumor and was able to have operation after.
Sincerely
Muri