Treatments for halting the growth of cancer-feeding blood vessels could be key to treating tumors. This term is known as anti-angiogenesis. The Angiogenesis Foundation has listed 32 Dietary sources of naturally-occurring anti-angiogenic substances.
William Li (and his Youtube video: can we starve cancer?) makes a great case on pre-eliminating possible cancerous growth by changing our food consumption to include sources that impede the blood feeding these growths need.