It is possible for "lesser" qualified students to match in rad onc. This field is not as numbers-based as some other fields. That is what is so scary about applying to it. Some positions are all about who you know. You do well at you home institution on an elective rotation, and you can get the spot with subpar scores. I recently spoke with the program director at my school. He was not impressed at all with my >260 usmle, good 3rd year grades, etc. He told me that board scores really don't matter at all for his position. Instead, he said that that it was much more important for me to do an elective rotation to show the attendings that I am legitimately interested in the field and that I am someone that they can work with with for 4 years.