Welcome @rra815, As @eku noted, there is an extensive discussion about CA 27-29 marker. I took the liberty of moving your question to the existing discussion here:
- CA 27-29 numbers rising: Does anyone else have an issue like this? https://connect.mayoclinic.org/discussion/ca-27-29-consistently-high-in-the-40s/

You ask "Is there a better way to test for recurrence?"
My understanding is that indications of recurrent breast cancer are based on results of mammogram or physical exam, or because of signs and symptoms. Then additional tests are done to confirm the diagnosis. Some oncologist may use CA27-29 along with regular mammogram, but it can be unreliable and is never a definitive indicator. Further testing must be done to confirm.