My mom recently started taking Xalkori (Thursday) to treat lung cancer. She has various symptoms which seem associated with the cancer, most notably difficulty swallowing (liquids, not solids). However her difficulty breathing has seemed to worsen since she started taking Xalkori. I have read that is a possible side effect (albeit rare) of Xalkori. At what point is the difficulty breathing associated with the cancer, vs. a side effect of the drug? The website makes it sound like I should contact my healthcare provider immediately. It s not like she s gasping for air, but it does seem worse (wasn t really a symptom before). How concerned should we be? Thanks.