Or will having MD along with a fellowship be sufficient?
Also, for people who did MD/PhD, do they still have to go through residency? So for example, I'm interested in the field of radiation oncology and would like to practice it as well as researching better methods, etc to treat cancer. Would I have to go through the 8-9 years of MD/PhD, then another 3-4 years of residency in radiation oncology?
Thanks!
I've done my Master's in Medical Physics in a program largely geared towards rad-onc physics, although I'm mainly into imaging myself, I have a good picture of rad-onc research at my university anyways. A lot of the new technical developments, treatment planning, image guided therapies, tomotherapy, IMRT, protons, etc. are very much physics driven, most of the RadOncs I've seen involved are used mainly for a referral base for small trials, although they are more heavily involved in documenting larger multicenter clinical trials. Depending on what you see as your primary role, you may want to consider looking at some clinically oriented medical physics graduate programs. Clinical physicists do play an important role in patient management, albeit with little to no patient interaction, and are currently pretty well compensated as well. Google the AAPM website for more info, as its probably a more direct route to rad-onc research.
As for whether or not you require a PhD to do rad-onc research, probably not, but it will potentially allow for a broader scope in the type of research you would likely do as a rad-onc. None of the rad-oncs involved with our department have PhD's, although some have Master's.
Also, it's a field where in the US, a high proportion go into private practice. To work at large academic centers where research is focused, a fellowship is almost a must, with or without a PhD.
If you want your main focus to be clinical with occasional research, don't do the PhD. If you want to do research that is heavily technically oriented or 100% research, and potentially have some involvement in patient care, consider medical physics instead of medicine. If you're still dead set on medicine and a heavy research involvement you could probably do alright with just a Master's. Do the PhD if you feel it will help with your specific aims.
Try and come up with a picture of what balance you want to strike now, and let that guide your decision, knowing full well that picture will probably change in 10 years time anyways.
Check out the rad-onc forum as well, as they probably have a better picture of the funding/research environments in major American centers. (I'm Canadian, thankfully, and my experience is in Canada)