With cancer, unfortunately there is no guarantee that it will not come back again because the damage has already been done. Even with the best possible treatment available as on date, you will be declared "cancer-free" after 5 years. Alternative and natural therapies claim to do so however they are not accompanied by scientific evidence so I would not really recommend them. Problem with cancer cells is that you would not know if the microscopic spread/deposits has already happened elsewhere in the body because no diagnostic technology exists to detect it. While you get treated for local manifestations, you just have to wait and watch for others and that is why this particular disease requires regular followups. Probably in few years from now there maybe a means to detect and cure when researchers are able to identify why it happens. Probably there will be vaccine or methods to teach the body to fight cancer cells itself.

Till then you can just hope for the best and take good care of health to probably delay the recurrence, if it is in store for you in future. Not to demotivate you but it is better to have expectations right rather than getting disappointed.