Here's my humble take on the fact that the average USMLE Step 1 score is not as high as most would think it is.
There is a far higher percentage of MD/PhDs per available residency slot in rad onc than in other fields with similar average board scores (radiology, ortho, etc.). Newly graduating MSTP students (MD/PhDs) are listed in the same category ("U.S. Seniors") as all other more "typical" graduating seniors (those with just an M.D.). I believe that, given the advantage that MD/PhDs have in the match process with their extra years of research and publication potential, they simply do not need as high of a USMLE Step 1 score to match successfully. I think stephew said that she has seen many MD/PhDs match with 210s or lower, which I think would support my point.
I think that this fact skews the data a bit. For example, I believe if you took all of the U.S. seniors and excluded the MD/PhDs from the group, the average USMLE Step 1 of successful applicants would jump up to the 250 range instead of 230s as we see now.
This is my sense of things based on the data I've seen and what I've seen from successful applicants that I know personally.
I think with so few spots and so many PhDs applying each year, the competiveness of rad onc is still far above diagnostic rads and ortho and still in the ballpark with plastics and derm.
Sorry for my grim analysis. This is only my take on things.