Some people are selfish shits. Your 'friends' clearly fall into this group.
I cannot believe how many yabus you are getting.
When a friend is going through something horrendous, you should be there for them MORE, not less than when they were well.
You and your friends got together every week/fortnight and that was something they could both do. Until you tell them you have cancer and suddenly neither of them can do the weekly/fortnightly meetups with you because reasons (but they can still meet each other)
Invites came while you were well but when you told them you had cancer suddenly there's no invites for you but again, they're still hanging out.
They tell you they will be there for you AND say tell us what we can do and when you take them up on their offer, they cancel on you.
They text you, you've even got a group whatsap, soon as you tell them you have cancer it's instant tumbleweed.
I seriously doubt they both have terrible problems that have suddenly presented at the same time as each other and which coincidence with you telling them of your cancer and which prevents them from coming to see you, invite you out or have a chat but does not stop them socialising with each other.
You'd have to be an idiot to actually think this is anything other than them ducking out because they don't want to be the ones supporting op even though she has been there for them when they needed her.