Sorry to hear about your son I hope you are doing well with the treatment.
My daughter is also 18 and diagnosed with rhabdomyosarcoma it came from nowhere and after spinal surgery to save her from paralysis as the original tumour was wrapped around her spine she is now on round 8 of chemo. So far she is responding well but I'm not sure the cancer will all be gone when round 9 ends. She has been offered maintenance chemo which will continue for 6 mths to a year but is much less invasive. She remains so positive and believes she will get better, I admire her optimism but feel that she at only 18 is a little naive. But we fight on for a miracle!
