If you have not done this already go ahead and get the latest podcast from Pint of Science where we interview the chairman of my department, Sandy Anderson.
One interesting part of the conversation was about the evolutionary nature of cancer and how this could be compared to how we have been using antibiotics thus reaching the point in which they will become virtually useless.
The problem with the way we (ab)use antibiotics is that we use them all the time. Modern farming is based on the idea that we can keep lots of animals in close proximity without fear of diseases spreading. This consitutes a perfect ground for the emergence of superbugs: bacteria that are resistant to antibiotics. This means that we are running out of options for people that acquire an infection from one of these bacterial strains.
The situation is cancer is not the same: cancers are not infectious diseases. But inside a patient there are different types of tumour cells and trying to kill as many cells as possible could, without the help of some guidance (I would love to volunteer the help of mathematical oncologists) mean selection for those cells that we cannot treat.
Cancer Ecology 