Serum tumor markers: part II--practical considerations and limitations of testing.

The attributes of an ideal tumor marker are well beyond the capacity of the tests that are currently available. While some markers do an adequate job at the early detection of recurrence and as a means to monitor the efficacy of treatment, there are serious deficits regarding sensitivity and specificity. In addition, although they are easily measured and cost-effective, the limitations of immunoassays are also a detriment. PSA was used to illustrate many of the limitations and difficulties associated with tumor marker testing and cancer assessment. For the most part, however, it is a better marker than many of the other analytes examined for their corresponding malignancies. Nevertheless, PSA still has major limitations--as is the case for all tumor markers in current use. Although the use of tumor markers is widespread and they do have much to offer, clinicians need to be made aware of their limitations, which can be achieved through good communication between laboratorians and the caregivers who are ordering the tests.