My mom is a smoker. she has had a non productive cough for about a year now. today was complaining about upper back pain. can it be her lung? cancer?

May need some Tests: Persistent cough can be due to smoking(bronchitis) or other lung diseases. Since it has persisted for one year, you should get a medical check up to find the cause. A simple chest X-ray may reveal any obvious problems but a CT scan of the chest is even more detailed and more reliable test to find a cause like Cancer(which is unlikely) in the lung or in the back bones.