If you know someone that is going through cancer treatments, offer your help. Some times it's hard to accept help. Most people won't call and ask. Call occasionally with suggestions of things you can do. Bring a meal, drive their kids to school or activities, pick up groceries, drive them to the doctors, sit with them during treatments, clean their house, do yard work etc. Also, support their caregiver. They are going through a tough time too.
"Women agonize... over cancer; we take as a personal threat the lump in every friend's breast". ~Martha Weinman Lear