Cortisone fixes my hoarse voice. i get hoarse a few times a year. what is the chance that it is throat cancer?

Not likely: If the hoarseness were from cancer it would not go away even with cortisone treatment. You should consult your doctor to avoid further damage. If you smoke or use tobacco in any form, quit while you are ahead.

Very low.: Throat cancer would lead to a steadily progressive hoarse voice that would not substantially improve with steroid treatments. A more likely diagnosis would be vocal nodules or recurrent laryngitis.