Association of the presence of bone marrow micrometastases with the sentinel lymph node status in 410 early stage breast cancer patients: Results of the Swiss Multicenter Study

Background: The sentinel lymph node (SLN) status has proven to accurately reflect the remaining axillary lymph nodes and represents the most important prognostic factor. It is unknown whether an association exists between the SLN status and the presence of bone marrow (BM) micrometastases. The objective of the present investigation was to evaluate whether or not such an association exists. Methods: In the present investigation 410 patients with early stage breast cancer (pT1 and pT2 <= 3cm, cN0) were prospectively enrolled between 1/2000 and 12/2003. All patients underwent SLN biopsy and bone marrow aspiration. The histological examination of the SLN consisted of step sectioning, H&E, and immunohistochemistry (Lu-5, CK 22) staining. Cancer cells in the BM were stained with monoclonal antibodies A45-B/B3 against cytokeratin and counted by an automated computerized digital microscope. Results: BM micrometastases were detected in 28.8% (118/410) of all patients. The SLN contained metastases in 32.4% (133/410). Overall 51.2% of the patients (210/410) were SLN negative/BM negative and 12.4% (51/410) SLN positive/BM positive. Of all patients, 16.4% (67/410) were SLN negative/BM positive and 20.0% (82/410) SLN positive/BM negative.There was a statistically significant association between the SLN and BM status, both in unadjusted (Fisher's exact test: P = .004) and multiple logistic regression analysis (P = .007). Conclusions: In the present investigation a significant association was found between a positive SLN status and the presence of BM micrometastases. Nonetheless, the percentage of non-concordance (SLN negative/BM positive and SLN positive/BM negative) was considerable. The prognostic impact of BM micrornetastases in our patient sample remains to be evaluated.