In Buffalo, there is a GPR program at Roswell Park Cancer Institute which focuses on treating cancer patients. The program works closely with other medical specialists in building a comprehensive patient care regimen. A neat opportunity for those who are interested in this particular patient population.
I shadowed a dentist that treats kids and patients with special needs, it's very rewarding and I'm highly considering going into that myself. I'm not aware of any program specifically geared twords treating patients with special needs, just some courses here and there.
This is inaccurate. What you're describing is radiation oncology, which remains a medical specialty. Oral & maxillofacial radiologists, as another poster mentioned, is a diagnostic specialty, and exists almost exclusively within academia.
A dental sub-specialty that allows you to manage cancer patients is maxillofacial prosthodontics. It is your job to provide prosthetic appliances for patients after they have part of the jaw or face ressected from cancer so they can function in society. This management starts from pre-surgery work up to going to the OR to making final appliances. I do not mean to be biased but I can't think of another dental specialty that work so closely with cancer patients than MP. DP