The use of serum carcinoembryonic antigen to assess therapeutic response in locally advanced and metastatic breast cancer: a prospective study with external review.

Serum carcinoembryonic antigen (CEA) has been measured throughout initial systemic endocrine treatment in 87 patients with stage III and 179 patients with stage IV breast cancer. Clinical response has been assessed after six months according to UICC criteria with external review of clinical and radiological data. Pretreatment CEA concentrations have been compared with those found in 55 'disease free' women attending a diagnostic breast clinic. A strong correlation exists between therapeutic response and alterations in CEA concentration (above 6 ng/ml) in patients presenting with stage IV disease. More than 50% of such patients either present with or develop CEA concentration greater than 6 ng/ml during the first six months of treatment.