The answer to these two questions are inter-related and equally important to understand when trying to compare tried and true treatments like IGRT to other treatments.
Let's use prostate cancer as an example. Since prostate cancer is so slow-growing, a large percentage of men may have no significant growth in their prostate cancer for many, many years, even if they are given no treatment at all! This is called the Natural History of Prostate Cancer - we know it is slow growing.
Now let's say that we gave these men a sugar pill, or placebo, as treatment. Since this cancer is slow growing, as its natural history suggests, it is quite likely and very possible that these men would be doing well at 5 years, or even at 10 years. So were they "cured" by the placebo? Unfortunately, by 15 years it is more likely that the cancer would grow despite the placebo and eventually all of these men would likely die as their cancer grew unchecked by this "phantom" sugar pill/placebo treatment.
Much the same idea, these "newer" treatments, such as Cyberknife or HIFU, which sound exciting, cannot in our opinion be judged effective until there is more than 10 years of data to compare, since with no treatment these patients would likely be doing well anyway. Until that time where we understand if the patient was helped by this "new technology" or learn whether it was just the natural history of a slow growing cancer that saved the patient's life. Until these technologies have 10 years or more of substantial, data these technologies in our opinion must be viewed as experimental. We recommend that patients strongly consider whether they want to forego treatments like surgery or radiation, which have decades of proven data behind them, before trying technologies that are not proven beyond 10 years. Until such 10-year data is available, n one truly knows whether patients' ultimate outcome will be better, the same or worse than the proven therapies of surgery or IGRT-based radiation. But who knows...?