Try and meet with the social worker at the hospital to learn about aid and resources available.They varry in levels of assistance so you might have to talk to a couple of them to get the information you need. Also try and meet with an ACS person at a cancer center near you to also assit you with information on help available. My Mother lived 2 hours each away also. I pulled my kids out of school 9 and 10 years old at the time and I home schooled them so i could have flexability in my schedule to go and care for my Mom. I am so glad I did this since I hold onto that time and I have no regrets because i did all I could. And my children learned that caring for family is the most important thing in life..I have a sister who lived just 5 minutes away but she wouldn't do a thing for my Mom. And her two grown up daughters have not learned what family is about and this breaks my heart also.
Perhpas your college sons can get some flexability in their schedule and thier work to help you care for your Mom. I know its hard but this is a life lesson time..something they will carry with them. Consider other relatives too.
This is a very important segment of your life. Take a deep breath and think carefully about the entire picture and how your Mom can be best cared for. My Mom did not die of her cancer. She had a stroke and she passed very quickly. I thank God for that and letting me be with her right to the end.