Bone marrow micrometastases in primary breast cancer: Prognostic significance after 6 years' follow-up

Using an antiserum to epithelial membrane antigen we have screened multiple bone marrow aspirates from 350 patients with primary breast cancer taken at the time of initial surgery. 89 (25%) patients were found to have micrometastases and their presence was related to pathological size (P < 0.01), the presence of peritumoral vascular invasion (P < 0.001), and positive lymph nodes (P < 0.005) but not menopausal status. At a median follow-up of 76 months (range 34–108) 107 patients had relapsed with distant metastases. 48% (43 of 89) of these patients had micrometastases initially compared with 25% (64 of 261) who did not (P < 0.005). The test predicts for relapse in bone (P < 0.01) and other distant sites excluding bone (P < 0.001) and is associated with a shorter overall survival (P < 0.005). We conclude that the detection of micrometastases signals a high likelihood of early relapse and decreased survival in breast cancer.