I highly doubt that you could cancel your score and I would also not recommend it. Many people have been shocked to see a passing score when they were sure that they had failed. You have two choices: 1) Continue to study for REG or 2) move on and study for the next section until you find out if you passed or not. I always chose to start studying for the next section but I've seen plenty of people say that they would review and keep studying REG. The way I looked at it is that I could just go back to restudy the section if I didn't pass but if I continued to study the same section and found out I passed it would be wasted time. Good luck and let us know what happens.
i dont think you can cancel. if you are truuuly 100% sure you failed, you probably failed by a lot. so, you probably want a good amount of time to study anyway. just study until the score is out and you can reapply!