Should I tell my childs father that our son has cancer?

My son is a little over a year old and his father has been absent in his life. He left me when I was pregnant because I wouldn't get an abortion.He ended up going back to his previous baby mother and their two children. He is great to his two children with her but acts like mine doesn't exist. I had to take him to child support because he refuses to give me money. It's been a year and even though child support has been established, I have received nothing. He is facing up to 60 days next month for non-payment. He has made up lies to the court and asked for an emergency order of protection stating that I've been following him and it was granted without me being there to defend myself. I never even called this man or harred him. I am ashamed he is my sons father. The last time he called to check on my son was 2 months ago. During that phone call, I told him our son was sick, but he didn't care. I since found out that the sickness is cancer. It's been a month since I've found out and my son is going through chemotherapy. I haven't told him as of current what is going on with him. Should I tell him or just leave it alone. He has showed in so many ways that he doesn't care about me or my son. I dont know what else to do?