Pretty sure he didn't imply that cancer drives evolution.
wikipedia on cancer: "A large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body.... Cancer occurs when problems in the genes of a cell prevent these controls from functioning properly. These problems may come from damage to the gene or may be inherited, and can be caused by various sources inside or outside of the cell"
I think he implied that cancer is an inherent flaw in the gene based reproduction used by complicated organisms. That our genes' ability to mutate, which introduces new and evolutionarily selectable attributes during sexual reproduction, can play up because of things like "tobacco use, infection, radiation, lack of physical activity, poor diet and obesity, and environmental pollutants.", and lead to cancer.
I'm not saying it's totally 100% correct, although I suspect it is close, just explaining what I think he meant.
Cancer is a series of mutations that enable a single cell to out compete other cells in the body for resources and reproduce exponentially. The final stage of cancer is generally some cancer cells that learn how to travel though the body and end up in a new location. However, rather than a simple disease it's an evolutionary process than can result in a brand new parasite as long as the cells learn to adapt outside the original host.
http://en.wikipedia.org/wiki/Devil_facial_tumour_disease
Warning, clinking on that link may give you nightmares.
wikipedia on cancer: "A large group of different diseases, all involving unregulated cell growth. In cancer, cells divide and grow uncontrollably, forming malignant tumors, and invade nearby parts of the body.... Cancer occurs when problems in the genes of a cell prevent these controls from functioning properly. These problems may come from damage to the gene or may be inherited, and can be caused by various sources inside or outside of the cell"
I think he implied that cancer is an inherent flaw in the gene based reproduction used by complicated organisms. That our genes' ability to mutate, which introduces new and evolutionarily selectable attributes during sexual reproduction, can play up because of things like "tobacco use, infection, radiation, lack of physical activity, poor diet and obesity, and environmental pollutants.", and lead to cancer.
I'm not saying it's totally 100% correct, although I suspect it is close, just explaining what I think he meant.