After the introduction (1, 2) and methodical evaluation (3, 4) of a new method for the quantitative measurement of the bone isoenzyme of alkaline phosphatase (test-combination bone alkaline phosphatase, Boehringer Mannheim), we started a retrospective clinical study for the follow-up investigations of breast cancer patients. Our aim was to establish the significance of the routinely used tumour markers, CEA and CA 15-3, in combination with bone alkaline phosphatase for the early detection of

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... astatic spread to the bone. We investigated 492 sera from 92 patients suffering from breast carcinoma, and we compared each date of investigation with the results of the clinical examination and with the results of medical imaging, if that had been performed. From a previous study involving skeleton scintigraphy (5) we knew that single examinations do not allow a differential diagnosis between benign and malignant disorders of the bone, so we based our calculations on differences between sequential investigations. We found that in follow-up investigations of patients with breast carcinoma the combined determination of CEA, CA 15-3 and bone alkaline phosphatase may be indicative for the localisation of metastatic disease. The determination of the bone alkaline phosphatase is easy to handle with a short assay time and good reproducibility; it can therefore be recommended.