How can you evaluate the tumor marker test?

With a grain of salt: If you are asking about tumor markers like CEA or ca125, these are substances that can go up in certain cancer patients and are mostly useful to monitor response to therapy. They are not screening tests, they do not always go up if a cancer recurs, and they may go up for non malignant causes. They are a tool to be used as part of cancer management and are often misused, myself included.