The Obama administration plans to spend $1.1 billion over the next few years on studies to compare the effectiveness of competing treatments for common conditions like back pain, heart disease, and prostate cancer. The studies will be publicly released, to help doctors and patients decide which treatment options they want to pursue. Supporters include many medical researchers, consumer groups, unions, and insurers. But potential opponents warn that the comparative effectiveness movement could lead to inadequate treatment for some patients and even the rationing of healthcare.