Check out the scientific studies area of the Spring Forest Qigong section of our website. I believe we discuss a couple of studies regarding cancer.
You will also find on the website a testimonial from Dr. Neil Kay of the Mayo Clinic. This past spring he received funding to study the effects of Spring Forest Qigong on Breast Cancer.
He became interested in Spring Forest Qigong when his wife was healed of breast cancer after practicing Spring Forest Qigong. At the time he was head of breast cancer research (I believe) at the Virginia Piper Cancer Center at Abbott-Northwestern Hospital in Minneapolis.
If I had cancer I would follow Chunyi's advice:
Practice one to two hours every single day.
Use Qigong as a complement to any medical treatment you now receive. Do not change any medical treatment without telling your doctor. In other words, hedge your bet. Do everything you can.