I do echo your concerns. Qigong is not a cure for cancer, it is a way to make your body stronger to help you fight the medical conditions. If you start doing it too late - say at the advance stage of cancer, it may not be as effective. Even then, I have seen people healed with the use of qigong. In these cases, the healing results not only from the control of chi, that also the mental strengths brought forth by the focus of mind and the determination to overcome the medical conditions.