Bone marrow involvement in breast cancer: a retrospective cohort study

The incidence of bone marrow metastases is a rarely described manifestation of metastatic breast cancer (BC).

Clinical, laboratory and histopathological data were retrospectively analyzed in 50 women with histopathologically confirmed BC metastasis.

The median age was 68.3 years, and 60% of patients had an ECOG performance status of 0-1. Most cases were BC of no special type (n = 47; 94%), primary in 70% (n = 35). The luminal Human Epidermal Growth Factor Receptor 2 (HER2) - was the predominant biological subtype (n = 35; 70%). The most common indications for trephine biopsy were anemia and thrombocytopenia. Synchronous bone metastases occurred in most patients. Biological type 4conversion was seen in 16 cases (32%) and included luminal converting into triple negative BC (n = 6; 37.5%) and luminal HER2+ into luminal HER2- BC (n = 3; 18.75%). The median of overall survival (OS) was 9.2 months (95% CI: 6.3 - 14.9). High lactate dehydrogenase level (p = 0.023) and thrombocytopenia (p < 0.001) correlated with a shorter median OS. In multivariate analysis, low levels of platelets correlated with a lower median OS (p < 0.001). A positive correlation occurred between lymphocytes (p < 0.001), monocytes (p < 0.001) and the percentage of bone marrow infiltration. Higher neutrophil-to-lymphocyte ratio was associated with shorter survival (p = 0.02).

Bone marrow metastases indicate a poor prognosis. The high rate of receptor conversion highlights the importance of re-evaluating tumor biology after BC progression which may increase the scope of systemic treatment options and improve the prognosis.