This is an interesting discussion. Tumor marker tests are one tool doctors have to monitor but they can have great change and variables. It's good to have another option in testing but again, a doctor has to be careful how it is used and interpreted. Case in point.......my husband has CA27-29 tumor marker indicator that has gone from the 40's to 177 in the past year. Granted, he has a cancer of unknown primary which the doctors are now assuming might be lung cancer. We were concerned (as the doctors were) that at 177 it shows a great deal of cancer activity in his body. We know that is happening for him..........BUT..........during our discussion it came out that several factors, in addition to cancer, could be affecting the test including his COPD, his use of inhalers and his vaping of medical marijuana (which is prescribed).
Certainly my husband has cancer and the tumor marker test is showing that but whether it's showing progression in the blood of his cancer, the doctors can't say. Finding the right mix of tests and procedures at the right time for each patient is a real 'art' and one that unfortunately is still a work in progress.
Hugs