The way this is going to work, and work for rad oncs in practice, is for the ACADEMIC RAD ONCS to take on some of these additional responsibilities and to reshape our specialty.
Residency training is cultural training. If residents in other specialties are not "trained" during their residency years that rad oncs do other things besides just radiation, rad oncs will never get additional referrals. Radiation doesn't have a scope of practice problem, really... we have a get-referrals problem (and sure that is to large extent due to our reputation as more technical than physician-y). You have to train 'em young. We would need to train rad onc residents coming in, and the med onc, urology, etc., residents would have to see "Oh ,gee, I can hand some of this stuff off to rad onc, they do a good job with durva/hormones/what have you." Then when those med oncs and urologists get out in practice they will be more willing to yield some work because they were trained and saw it back in residency and it seemed normal.
The moment we have some weird side effect from Arimidex, we will need to refer , probably, to med onc. The only way that spoonful of medicine is going to go down is if it happened a few times during the med onc's fellowship training and he saw such instances as a normal fact of life versus the rad onc being stupid at oncology.
We will never make more money or get more relevance or more "reputation equity", I am afraid, if we all just started, today, in our practices, giving Temodar and Lupron and checking dexa scans etc. No one makes money from that "crap" first of all. (They make some money from infusions, true, and having their own pharmacy.) They make money from the constant spigot of referrals coming into their clinic IMHO. (And med onc has neat tricks whereby they're treating patients over much longer periods of time than rad onc; another story.)
So we all need to think this through and see what it is we are really asking and what we really want. We shouldn't care if we are relevant or not, or what our rep is. We should just care about getting more referrals and how to do more with the referrals we get. Of course, it is all connected: relevance, reputation, and referrals. To that end, academic rad onc will have to lead the way because it is academic RO who defines and shapes the culture of rad onc. This last sentence, though, sucks hope from my soul.