You are going to have to decide for yourself about your diet just like you have to decide to change how you breathe. My advice, if it is worth anything in terms of diet, is to incorporate the best of many dietary worlds and to stick to the basics. Of course you can listen to anyone of many experts and let the one your heart resonates with tell you what to do. From a scientific point of view the Ketogenic Diet is very interesting and so is fasting or intermittent fasting.
However, without doubt the strict vegetarian approach championed by Chis Wark and many others will help one conquer their cancer. It is worth the investment in time to study the alternatives and decide on which approach suits you best. But as the next chapter/lesson suggests, there is not shortage of nutritional causes of cancer so nutrition can and should be used to treat it.