By: Christopher Johnson, MDSource: KevinMD.comDate: July 20, 2013  Hardly a day goes by when some news outlet does not report, often breathlessly, some new breakthrough in cancer research. We need to turn a skeptical eye on most of these reports, particularly those that contain information about very preliminary research findings. The always astute Gary Schweitzer gives a good perspective on this in his HealthNewsReview.org; it’s a good site to bookmark if you follow the medical news. The key thing to remember is that many, many substances have been found to attack and kill cancer cells in the laboratory. The cartoon above, from the wonderful site xkcd, illustrates the problem. This is generally how promising anti-cancer agents are first identified: we test them against cancer cells growing in a dish. These are called in vitro (“in glass”) studies. But once a potential cancer treatment is found there is a long way to go. First of all, can the concentrations of the agent that showed cancer-killing activity in the dish be safely achieved in the body? And, if they can, does the agent still show that ability in the incredibly complex system of the body? Often such in vivo (“in life”) studies are first done in experimental animals before they are tried in humans. The testing process in humans is long and complicated. By convention it is divided into several phases. These are worth knowing about because the media will often enthusiastically report results from phase I trials, which represent very preliminary [...]