Bone marrow micrometastases do not impact disease-free and overall survival in early stage sentinel lymph node-negative breast cancer patients.

BACKGROUND: The presence of lymph node metastases is the most important prognostic factor in early stage breast cancer. Whether bone marrow micrometastases (BMM) impact the prognosis in sentinel lymph node (SLN)-negative breast cancer patients remains a matter of debate. Therefore, the objective of this study was to assess the impact of BMM on 5-year disease-free and overall survival among those patients.
METHODS: We analyzed 410 patients with early stage breast cancer (pT1 and pT2 ≤ 3 cm, cN0) who were prospectively enrolled into the Swiss Multicenter Sentinel Lymph Node Study in Breast Cancer between January 2000 and December 2003. All patients underwent bone marrow aspiration followed by SLN biopsy. All SLN were stained with hematoxylin and eosin and immunohistochemistry (Lu-5, CK-22). Cancer cells in the bone marrow were identified after staining with monoclonal antibodies A45-B/B3 against CK-8, -18, and -19.
RESULTS: Negative SLN were found in 67.6% (277 of 410) of the enrolled patients. Of those, BMM status was negative in 75.8% (210 of 277) and positive in 24.2% (67 of 277) patients. Median follow-up was 61 (range 11-96) months. Five-year disease-free survival was 93.6% (95% confidence interval [CI] 89.1-96.0) in BMM-negative and 92.2% (95% CI 82.5-96.2) in BMM-positive patients (p = 0.50). Five-year overall survival was 92.7% (95% CI 87.9-95.8) for the BMM-negative and 92.5% (95% CI 83.4-96.2) for the BMM-positive group (p = 0.85).
CONCLUSIONS: This is one of the first prospective studies to examine 5-year disease-free and overall survivals in SLN-negative patients in correlation to their BMM status. Although BMM are identified in one of four SLN-negative patients, they do not impact disease-free and overall survival.