I don't know how I missed this. I hope your grandpa does well with chemo. Your post made me tear up. I was really close with grandpa, he practically raised me and my younger brother. It was really hard to see him sick and frail.
Hopefully your grandpa will get better with the treatments. How did he find out about it in the first place? And pain or anything? My step-grandma on my mom's side (my mom was adopted, so not my blood grandma) passed from breast cancer, very rare for Asian women actually. She didn't speak up about the pain until it was too late, and it had spread into her spine, bones and lungs. We didn't even know she was sick. So hopefully your grandpa caught it in time for treatment. Keep us updated, I will be sending good thoughts to you and your family.