Serum tumour markers: how to order and interpret them

#### Summary points Tumour markers are molecules that may be present in higher than usual concentrations in the tissue, serum, urine, or other body fluids of patients with cancer.1 2 3 Serum tumour markers may aid cancer diagnosis, assess prognosis, guide choice of treatment, monitor progress during and after treatment, and/or be used as screening tests. Conservative estimates suggest that in the United Kingdom alone close to 15 million such measurements are made each year. If tumour markers are requested and interpreted correctly, they undoubtedly help clinical management. Somewhat alarmingly, however, a recent audit in a single Greek hospital found that only about 10% of requests for tumour markers were appropriate.4 The cost of inappropriate testing of tumour markers was estimated to be about €23 974 (£21 000; $35 000) a month, even without including the cost of unnecessary second level follow-up investigations such as colonoscopy and ultrasonography.4 However, awareness of the limitations of tumour markers is crucial not only because of the economic implications of their misuse but even more importantly …