Association of tumor angiogenesis with bone marrow micrometastases in breast cancer patients.

ABSTRACT

BACKGROUND AND PURPOSE: The microscopic detection of tumor cells (micrometastases) in bone marrow and the extent of blood vessel formation (angiogenesis) in primary tumor specimens are recognized as independent prognostic markers in patients with breast cancer. Since micrometastases occur as a consequence of interaction between the neoplastic cells and the tumor neovasculature, we have examined the relationship between these markers to determine whether the degree of angiogenesis is related to the presence of micrometastases. METHODS: Micrometastases were identified in bone marrow aspirates collected from multiple sites in 214 breast cancer patients prior to surgery (mastectomy or lumpectomy). Tumor cells were detected through an examination of epithelial membrane antigen expression and an analysis of cell morphology. Tumor vascularity was graded semiquantitatively or quantitatively (Chalkley point count) after immunohistochemical staining of the CD31 antigen expressed by the endothelial cells. The reproducibility and accuracy of the vascular grading were validated by use of kappa statistics. Associations between micrometastases and clinicopathologic characteristics, including angiogenesis, were examined using chi-squared and logistic regression techniques. All tests of statistical significance were two-sided. RESULTS: Of the 214 patients, 42 (20%) were positive for bone marrow micrometastases and 75 (35%) had tumors of high vascular grade. There was 86% agreement between vascular grades assessed twice for 35 tumors (kappa statistic = 0.66); for 22 evaluated tumors, there was absolute concordance between vascular grade and Chalkley point count. There were significant positive associations between tumor angiogenesis and micrometastasis (P = .01), tumor grade (P = .003), and estrogen receptor expression (P = .007); however, no significant associations were observed with tumor size (P = .9), lymph node status (P = .33), vascular invasion (peritumoral blood or lymph vessels) (P = .9), menopausal status (P = .17), or age (P = .12). Adjusting for confounding factors, multivariate analysis showed that only tumor angiogenesis (odds ratio = 2.7; P = .016) and vascular invasion (odds ratio = 2.7; P = .012) were significant determinants for the presence of micrometastases. CONCLUSIONS: This study suggests that an assessment of tumor angiogenesis and vascular invasion gives a reliable indication of the likelihood of the presence of bone marrow micrometastases in patients with breast cancer and that both processes contribute to metastases.