I actually think you would have a hard time having people agree to MD Anderson being a top PhD institution. Even Sloan Kettering may not be the best. You have to consider that although Sloan may have great output, the labs are not particularly well suited for students. The mentors are great but you will be competing with a dozen post docs for face time. Sure you will be on papers, but will you be forced to really think on your own. Although this is not always the case, it is a powerful argument to make and consider. US news considers Stanford, Harvard, and MIT to be amongst the top graduate programs in such area. I am surprised that no one has yet to mention these programs. But then again if you are going for a specific person, there are even a few great ones at smaller schools like University of Oregon.