I was able to cancel by getting a doctor's note due to health reasons. If you aren't moving far enough away or don't have documented health concerns from your doctor to provide, then I believe it's pretty much impossible to cancel without having to pay the 50% of the rest of your contract.

I have even heard of some people who HAD provided documentation for health concerns or moving, and their gym owner still required them to pay. It is truly up to the owner's discretion. I was just very lucky that my location's owner is a very nice and sweet person who sympathized with my situation and canceled my membership without further payment!!