Günter Schlimok

BACKGROUND: We assessed the prognostic significance of the presence of micrometastasis in the bone marrow at the time of diagnosis of breast cancer by means of a pooled analysis. METHODS: We combined individual patient data from nine studies involving 4703 patients with stage I, II, or III breast cancer. We evaluated patient outcomes over a 10-year follow-up period (median, 5.2 years), using a multivariable piecewise Cox regression model. RESULTS: Micrometastasis was detected in 30.6 percent of the patients. As compared with women without bone marrow micrometastasis, patients with bone marrow micrometastasis had larger tumors and tumors with a higher histologic grade and more often had lymph-node metastases and hormone receptor-negative tumors (P<0.001 for all variables). The presence of micrometastasis was a significant prognostic factor with respect to poor overall survival and breast-cancer-specific survival (univariate mortality ratios, 2.15 and 2.44, respectively; P<0.001 for both outcomes) and poor disease-free survival and distant-disease-free survival during the 10-year observation period (incidence-rate ratios, 2.13 and 2.33, respectively; P<0.001 for both outcomes). In the multivariable analysis, micrometastasis was an independent predictor of a poor outcome. In the univariate subgroup analysis, breast-cancer-specific survival among patients with micrometastasis was significantly shortened (P<0.001 for all comparisons) among those receiving adjuvant endocrine treatment (mortality ratio, 3.22) or cytotoxic therapy (mortality ratio, 2.32) and among patients who had tumors no larger than 2 cm in diameter without lymph-node metastasis and who did not receive systemic adjuvant therapy (mortality ratio, 3.65). CONCLUSIONS: The presence of micrometastasis in the bone marrow at the time of diagnosis of breast cancer is associated with a poor prognosis.

BACKGROUND: Cytokeratins are specific markers of epithelial cancer cells in bone marrow. We assessed the influence of cytokeratin-positive micrometastases in the bone marrow on the prognosis of women with breast cancer. METHODS: We obtained bone marrow aspirates from both upper iliac crests of 552 patients with stage I, II, or III breast cancer who underwent complete resection of the tumor and 191 patients with nonmalignant disease. The specimens were stained with the monoclonal antibody A45-B/B3, which binds to an antigen on cytokeratins. The median follow-up was 38 months (range, 10 to 70). The primary end point was survival. RESULTS: Cytokeratin-positive cells were detected in the bone marrow specimens of 2 of the 191 control patients with nonmalignant conditions (1 percent) and 199 of the 552 patients with breast cancer (36 percent). The presence of occult metastatic cells in bone marrow was unrelated to the presence or absence of lymph-node metastasis (P=0.13). After four years of follow-up, the presence of micrometastases in bone marrow was associated with the occurrence of clinically overt distant metastasis and death from cancer-related causes (P<0.001), but not with locoregional relapse (P=0.77). Of 199 patients with occult metastatic cells, 49 died of cancer, whereas of 353 patients without such cells, 22 died of cancer-related causes (P<0.001). Among the 301 women without lymph-node metastases, 14 of the 100 with bone marrow micrometastases died of cancer-related causes, as did 2 of the 201 without bone marrow micrometastases (P<0.001). The presence of occult metastatic cells in bone marrow, as compared with their absence, was an independent prognostic indicator of the risk of death from cancer (relative risk, 4.17; 95 percent confidence interval, 2.51 to 6.94; P<0.001), after adjustment for the use of systemic adjuvant chemotherapy. CONCLUSIONS: The presence of occult cytokeratin-positive metastatic cells in bone marrow increases the risk of relapse in patients with stage I, II, or III breast cancer.

According to the present view, metastasis marks the end in a sequence of genomic changes underlying the progression of an epithelial cell to a lethal cancer. Here, we aimed to find out at what stage of tumor development transformed cells leave the primary tumor and whether a defined genotype corresponds to metastatic disease. To this end, we isolated single disseminated cancer cells from bone marrow of breast cancer patients and performed single-cell comparative genomic hybridization. We analyzed disseminated tumor cells from patients after curative resection of the primary tumor (stage M0), as presumptive progenitors of manifest metastasis, and from patients with manifest metastasis (stage M1). Their genomic data were compared with those from microdissected areas of matched primary tumors. Disseminated cells from M0-stage patients displayed significantly fewer chromosomal aberrations than primary tumors or cells from M1-stage patients (P < 0.008 and P < 0.0001, respectively), and their aberrations appeared to be randomly generated. In contrast, primary tumors and M1 cells harbored different and characteristic chromosomal imbalances. Moreover, applying machine-learning methods for the classification of the genotypes, we could correctly identify the presence or absence of metastatic disease in a patient on the basis of a single-cell genome. We suggest that in breast cancer, tumor cells may disseminate in a far less progressed genomic state than previously thought, and that they acquire genomic aberrations typical of metastatic cells thereafter. Thus, our data challenge the widely held view that the precursors of metastasis are derived from the most advanced clone within the primary tumor.