We compared the course of the tumour markers CEA and CA 15-3 with the clinical course of 62 patients with metastasising breast cancer. The patients were treated by an aggressive chemotherapy (FAC-regimen) or high-dose hormonal therapy (1000 mg MPA/day). The markers were determined after a well-defined schema. In patients treated with aggressive chemotherapy, the markers were determined 4, 8 and 12 hours as well as 7 days after each course. In patients treated with hormonal therapy, the markers were determined weekly from the first to 12th week as well as 4, 8 and 12th week after onset of therapy. The course of the tumour markers was compared with the results of the radiological and clinical staging three months after beginning of therapy. For patients treated with aggressive chemotherapy CEA withdrawn 4 hours after the first and second cycle resulted in medium predictive values of 88 % for marker increase and 93 % for marker decrease. In comparison, the predictive values of CA 15-3 were 81 % for marker increase and 71 % for marker decrease. Both markers obtained better results when withdrawn four hours after therapy compared to values withdrawn 7 days after therapy. In high-dose hormonal therapy, the determination of markers collected four weeks after onset of therapy is sufficient for predicting the clinical course. The medium predictive values of CEA after 4 and 8 weeks amount to 83 % for marker increase and 87 % for marker decrease. In comparison, the predictive values of CA 15-3 are 95 % vs. 85 %. Thus, we recommend the determination of CA 15-3 every 4 weeks for monitoring the clinical course under high-dose hormonal therapy. In addition, our results indicate, that the simultaneous determination of both markers is not superior to single marker determination.
