For many cancer survivors, drugs can impair balance. If you've had chemotherapy, then you'll need to be even more careful, as the decreased bone-density will make you more prone to injury if you fall.
Therefore, working to improve your balance is an important part of recovering from cancer. Try standing next to a chair or raining (so you have something to grab if you need it), and alternate standing on one leg.
WebMD has a number of balance exercises you can try, or talk to your doctor about exercises they recommend.