Hi Linda,
I have absolutely no idea if the reaction to whole brain radiation is different when the lung cancer being treated is small cell vs. non-small cell; but my husband endured wbr in October 04 for NSCLC with mets to the brain and he felt really good during the treatments; however, almost as if his body knew it was okay, the day after his final treatment he went to bed and pretty much stayed there for almost two weeks....literally. He had about a zero appetite having to force down vitamin shakes and an occassional (very)low grade fever in addition to his fatigue. Not trying to scare you, everyone reacts differently; but when it did finally hit him, it scared the hell out of me. After about 2 weeks, he slowly began getting his strength and appetite back and feels wonderful now. I hope your sister endures the treatment well and gets good results. Let us know.