Beyond a certain point of growth, cancer cells, like any other cells, need blood vessels to provide them with nutrients and dispose of waste.
Angiogenesis is the process by which new blood vessels are formed in living tissue. Although the term, in and of itself, is not obligatorily attached to cancer, it is usually used in this sense; that’s to say the ability of cancer cells to invoke the creation of new blood vessels in tissue, thus assuring their nutritional needs and allowing them to continue to grow.
Controlling angiogenesis as a method of cancer treatment is thus a major field of current research.
The therapeutics company Amgen has put up an absolutely amazing Flash animation explaining the process of cancerous angiogenesis. This is really, really well done and an excellent illustration of just how powerful the web can be for educational purposes.
Don’t be frightened off by their use of medical terminology: the supporting animations are so well done that even a novice can keep up and learn a lot on this promising therapeutic path for cancer treatment.