Occult lymph node metastases not linked to overall survival in early breast cancer
Sentinel lymph node (SLN) metastases detected by immunohistochemical staining in women with early stage breast cancer who had undergone breast-conserving therapy was not associated with overall survival over a median of 6.3 years in a large study. However, occult bone marrow metastasis, while rare, was linked with decreased survival.
Billed by the investigators as the largest prospective trial to assess immunochemically detected metastases in the SLNs and bone marrow of women with early stage breast cancer, the American College of Surgeons Oncology Group Z0010 trial was designed to determine the connection between survival and metastases detected by immunochemical staining of SLNs and bone marrow specimens in such patients.
The project involved 5,210 women with clinical T1 to T2N0M0 invasive breast carcinoma, enrolled at 126 sites from May 1999 to May 2003. All participants had undergone breast-conserving surgery and SLN dissection.
Of 3,326 SLN specimens examined by immunohistochemistry, 349 (10.5%) were positive for tumor, as were 104 of 3,413 bone marrow specimens (3.0%). Five-year overall survival rates were similar for women with and without immunohistochemical evidence of disease: 95.7% for the immunohistochemical-negative women, and 95.1% for those with immunohistochemical-positive disease.
Occult bone marrow metastases were associated with decreased overall survival only when clinicopathological factors were not considered. “Bone marrow examination with immunocytochemistry may identify high-risk women,” acknowledged the investigators (JAMA. 2011;306;385-393; http://jama.ama-assn.org/content/306/4/385.full.pdf+html). “However, the incidence in the Z0010 trial was too low to recommend incorporating bone marrow aspiration biopsy into routine practice for patients with the earliest stages of breast cancer.”
Ultimately, the research team concluded that routine immunohistochemical examination of hematoxylin-eosin-negative SLNs and routine immunocytochemical examination of bone marrow are not clinically warranted for early-stage clinical T1-T2N0 breast cancer.