An objective biochemical assessment of therapeutic response in metastatic breast cancer: a study with external review of clinical data.

A series of tumour related markers have been examined in 179 patients receiving primary endocrine therapy for metastatic breast cancer. Significant correlations between therapeutic response (UICC criteria after 6 months of treatment) and appropriate alterations in serum concentrations of carcinoembryonic antigen, ferritin, c-reactive protein, orosomucoid and the erythrocyte sedimentation rate, have been observed when changes in these markers were examined only at high serum concentrations. By combining these five markers a 'therapeutic index' of response has been devised which can be employed at an early stage of treatment in more than 90% of patients, giving an overall sensitivity/specificity of 90%/78% for therapeutic response or disease stabilisation over a 6-month period. The design of an objective measurement of response, which is easy to perform, has the potential to replace the existing, largely subjective. UICC criteria for retrospective judgement of response, and may also be used to direct systemic endocrine therapy.