The objective measurement of remission and progression in metastatic breast cancer by use of serum tumour markers. European Group for Serum Tumour Markers in Breast Cancer.

An established biochemical index for monitoring therapy in patients with metastatic breast cancer was tested prospectively in a multicentre study. The index uses two serum tumour markers--carcinoembryonic antigen (CEA) and carbohydrate antigen 15-3 (CA15-3) along with erythrocyte sedimentation rate (ESR). 67 patients treated by either endocrine or chemotherapy had CA15-3, CEA and ESR measured at diagnosis of metastases and sequentially during therapy. Two markers, CA15-3 and CEA, were measured on a further 16 patients giving a total of 83 patients who were assessable for CA15-3 and CEA. Of the patients with CA15-3, CEA and ESR measured at diagnosis of metastases 84% (56/67) had elevation of 1 or more markers. During therapy the number with elevated marker(s) rose to 96% (64/67). Changes in the markers were in line with and often pre-dated therapeutic outcome as assessed by the International Union Against Cancer (UICC) criteria both for remission and progression. Patients without elevation of markers on diagnosis subsequently showed a rise in the marker(s) at or before documented disease progression by UICC. The 3 women in whom markers were at no time significantly elevated remain in remission. The results using CA15-3 and CEA were similar but 12% less patients were assessable. CA15-3 and CEA (with and without ESR) provide an objective method to guide therapy in patients with metastatic breast cancer.