Need advice on what is the the best way to treat someone who has cancer?

With compassion: Be supportive and available to help, such as run errands or grocery shop. Be a good listener, but don't be too inquisitive. Do not be maudlin and crestfallen. Rather, be as upbeat as possible. Many people with cancer do very well once initial treatments are completed. Leave the medical treatments to the doctors, and be a good friend and family member. Good luck.