Hi Tom,
Welcome to the site although I am sorry that you have to be here. And I am sorry to hear about your sister. Lainy is right in that a 2nd or 3rd opinion could be looked at if you have not already done that. I can’t help you with the chemo drug that you mention as my dad never had chemo or radiation. He had photodynamic therapy, PDT, as his only treatment. I don’t know if this would be suitable for your sister or not, but I guess that it is something that might be worth discussing with your sisters doctors.
I hope that you will keep coming back here as you will get a lot of support from us all, and if we can help in any way at all then we will.
My best wishes to you and your sister,
Gavin