Money, money, money . . . MONEY!
Rad Oncs got to have it, Derms really need it. Do things, do things, do things, bad things with it.
--------------------------------------------------------------------------------------------------
But seriously, it's all about referral patterns. As the perpetual "bottom feeders" of the referral hierarchy, Rad Oncs require referrals to sustain themselves. There are virtually no patients who walk through my door saying, hey I saw your fancy ad (on the interstate, on TV, on the radio, in the paper) and I want you to treat my cancer!
Skin patients have to come from Dermatologists (or PCPs to a far lesser extent). When Derms see the ridiculous revenue that you are pumping out of THEIR skin cancer patients, they buy the machine themselves, employ a Rad Onc/RTT/Physicist themselves and have at it.
Alternatively, they can buy the machine and contract Rad Oncs to provide the professional services. However, if you've ever done skin e-brachy you will understand when I say it is probably one of the most professionally unsatisfying clinical experiences. No contours, no rigorous thinking, no literature review, no bonding with patients, etc. They just show up (usually in a wheelchair or motorized scooter from a SNF) - you plop 'em on the exam table, draw a little circle around their BCC/SCC and that pretty much ends your clinical involvement.
Given the scenario above, most Rad Oncs in a practice do not wish to do e-brachy full-time which leads to problems with patient continuity. Hence, Derms try to hire a full-time Rad Onc to do it when their profit margin hits a certain point.