Can ct scan miss lung cancer ? can an mri find it while doing scan on thorastic spine? both without contrast

It depends: Lung cancer shows up in the lungs in nearly all cases but sometime sit can be occult(too small to be easily visible). But 95% of the time a ct scan of the chest(lungs) will show it up easily.

Both: Yes. And yes. However, since mris are very hard to obtain of the lungs due to lung movement, ct scans are much more useful and diagnosing lung cancer.