cancer vs. breathing issues

My mom's lung cancer seems to have come back.  She has a malignant lung tumor removed in 07.  She had the malignant lung tumor treated with Cyberknife radiation.  Not the oncologist & surgeon seem to feel that her breathing is more of the issue than the cancer.  I am real concerned.  She has been on 2.0 oxygen full time.  She uses inhalers.  Please see my previous question regarding how long my mom has.  Can anyone tell me is they have had a similar situation?  Thanks and God Bless.