No supporting friends

A few months ago my mom was diagnosed with cancer. Back then I told my friends about it and I told them I had a hard time dealing with it. They told me they would be there for me. To this day they have never asked about my mom. Not how she is doing, not how I’m doing. I can’t let go of it because they are my only close friends. I feel really sad about it and can’t deal with the fact that my best friends do not seem to care about this difficult situation. I know I can tell them this but that doesn’t change the fact that they were/are not here for me. Should I talk to them about it? I find it hard because I don’t know how to do it.