My mom had the same thing about 5 years ago in her throat. It was a stressful time, but she was strong as I'm sure he will be. The pregnancy will only make him fight harder!!
Just wanted to send you some hugs and give you some hopeful news. My very good friend's sister was diagnosed with this 6 months ago - she had to be on chemo every two weeks and the prognosis was very good. 6 months later, she is cancer free! I hope the same holds true for your BIL.