in a large field like internal medicine, the stats show that if you rank 7 programs, you will have something like a 95 or 97% chance of matching at one of the 7. however, these figures dont hold up for radonc, given the competitiveness. i ranked 12 and didnt match. i heard of someone ranking 17 and not matching. i had a friend who ranked 4 and matched. i even had a friend (a foreign medical grad) who ranked 1 optho program and matched. interview and rank as many as possible. there are no guarantees!