It's not the cancer or the lack of it that is the will of God in that verse in 1Thes 5. It is the giving of thanks in every thing. Don't try to make it something it is not.
Yes, we are to give thanks
in everything. Even in cancer, we are to give thanks to God the healer, for healing. That's faith.
Sorry but I had to make the point because I have seen many people think that they should give thanks for cancer.
