I do not know about Anti-cancer supplements but I will tell you my experience with building my immune system...
Last year I had a positive blood test for mono. I am in my 50's and had been feeling fatiqued and have several incidents of "colds" and respiratory type infections for about a year. I also had several bouts of cold sores in my nose, on my face and lips over a period of a year.
I tried several immune building type herbs from my health food store. Most of them included olive leaf with other herbs. For some unknown reason the ones I took seemed to make me sick to my stomach or make me feel worse.
I found some supplements specific for fatique and building a suppressed immune systen which were a Multi B vitamin pill and a additional supplement powder you mix with water that contained several other vitamins and herbs. I also took Acidophilus perals which is also recommended to support the immune system.
I have been well using these supplements since last Sept. No colds, resp. infections or cold sores all winter. I do not know if the supplements got me well or I would have gotten better anyway but I will keep taking these supplements. I have tried many other supplements and these seem to work the best for me.