There has been a lot of research into the effects of mushrooms in fighting cancer. In Japan, purified mushroom compounds are given alongside chemotherapy and radiotherapy.
Mushrooms are currently being studied for their anti-tumor, immunomodulating and anti-metastasis properties. Researchers are looking into whether they can be preventative as well as therapeutic. This doesn't mean you should go out and binge on mushrooms, too much of anything is probably not good for you. But the results in the lab, and research to this point, suggest mushrooms should be at the top of the list to add to your cancer-fighting diet.
If you don't like the taste of mushrooms, there are supplements you can take. Make sure you do your homework and select a good quality product.