It's just a bunch of cells in the wrong place

It's not malevolent
It's not even sentient
It doesn't have direction
It doesn't have agency
It doesn't have intent
It doesn't have feelings
It doesn't know any better
It's just doing what it was made to do

Every other cell in your body is on your side
Every cell of yours is under your control

Every cell on the outer edge of the tumour has to defeat one of yours to progress
You can make it as hard as possible for that to happen

Not only is the tumour completely surrounded by your cells, all of which are working for you, but it's going to be facing Modern Medicine

You have all the power
The only power it has is the power you allow it
If you give it a personality, or agency, you are giving it power
If you find yourself feeling anything about it, feel sorry for it

Because it's just a bunch of cells in the wrong place