A Mother's Worst Nightmare

My 29 year old newly married daughter was recently diagnosed with advanced stage colorectal cancer and has just started treatment. I've tried to find  a caregiver support group but the two I found are comprised of spouses, partners or adult children caring for a parent. I need to share/vent/cry with other mothers who are suffering the pain of a seriously ill child. I am not uncaring or dismissive about the pain anyone feels but a mother's suffering for a child is in a special class. Is there anyone else going through something similar? Please respond. Thank you.