I've watched this video before, and Dr. Li includes a very interesting statistic: cancer is 95% environmental and 5% genetic. If that's true, then his argument in favor of antiangiogenesis seems even stronger. The idea is pretty simple; you essentially consume foods with antiangiogenic properties meaning that they inhibit or slow the growth of blood vessels. Thus, if a cancerous tumor were to develop, its ability to grow would be severely curbed due to lack of (access to a) blood supply. Also, it turns out that the chance of metastasis is severely reduced, too, because the cancer can't travel by way of the blood supply.