Micrometastases in Sentinel Node Don’t Worsen Breast Cancer Survival

Posted on July 29th, 2011 by

Detection of very small areas of cancer (micrometastases) in the sentinel lymph node through use of highly sensitive testing is not associated with breast cancer outcomes. These results were published in the Journal of the American Medical Association.

For women with early breast cancer, determining whether the cancer has spread to the axillary (under the arm) lymph nodes is an important part of cancer staging. Many women initially undergo a sentinel lymph node biopsy, in which only a small number of nodes (or even a single node) is removed. If the sentinel nodes show evidence of cancer, many women then undergo additional lymph node removal.

For some women, evaluation of the lymph nodes will reveal very small areas of cancer known as micrometastases. Whether these very small areas of cancer affect breast cancer outcomes has been uncertain.

To explore the relationship between sentinel node micrometastases and breast cancer outcomes, researchers evaluated information from more than 5,100 women with early-stage breast cancer. Women were treated with breast-conserving surgery, sentinel lymph node biopsy, whole-breast radiation therapy, and (when appropriate) chemotherapy and/or hormonal therapy.

Women whose sentinel nodes were cancer-free by conventional testing underwent additional, more sensitive testing in order to identify very small areas of cancer that were not detected by initial testing. Researchers also collected bone marrow samples in order to detect small areas of cancer in the bone.

  • Of the sentinel nodes that tested negative (cancer-free) by conventional testing, 10.5% tested positive for micrometastases by more sensitive testing. The presence of micrometastases, however, did not affect overall survival or the risk of cancer recurrence.
  • Three percent of the bone marrow samples tested positive for cancer. Small areas of cancer in the bone marrow did appear to be linked with worse breast cancer outcomes, but the small number of affected women makes it difficult to draw firm conclusions.
  • Current approaches to breast cancer treatment may have contributed to the effective management of sentinel node micrometastases. A majority of the study participants received chemotherapy.

These results suggest that micrometastases in the sentinel nodes do not significantly affect the outcome of early-stage breast cancer. Highly sensitive testing to detect lymph node micrometastases does not appear to be warranted.

Micrometastases in the bone marrow may predict worse breast cancer outcomes, but do not appear to be common enough in early breast cancer to warrant routine testing.

Reference: Giuliano AE, Hawes D, Ballman KV et al. Association of occult metastases in sentinel lymph nodes and bone marrow with survival among women with early-stage invasive breast cancer. Journal of the American Medical Association. 2011;306:385-393.

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