When early-stage breast cancer is removed, the lymph node or nodes closest to the cancer -- the sentinel node(s) -- usually are removed and sent to a pathologist for evaluation. Removing just these nodes is called sentinel node biopsy or sentinel node dissection.
Sometimes when the sentinel node is found to have cancer in it, other underarm (axillary) lymph nodes will be removed. This is called axillary lymph node dissection or axillary node biopsy. Even when the pathology report says there is no cancer in the sentinel node, there can still be very small clusters of cancer cells (called micrometastases) in the sentinel lymph node and other axillary lymph nodes.
Results from the large B-32 study presented at the Multidisciplinary Breast Cancer Symposium in September 2011 found that women who had sentinel node biopsy did just as well as women who had axillary node biopsy, even though small clusters of breast cancer cells may have been in the axillary lymph nodes of the women who had sentinel node biopsy.
The B-32 study was done through a large, ongoing breast and colon cancer research effort called the National Surgical Adjuvant Breast and Bowel Project (NSABP). The B-32 study included more than 5,600 women diagnosed with early-stage breast cancer. None of the women had obvious signs that the cancer had spread to the lymph nodes. Half the women were randomly chosen to have axillary node biopsy and half had sentinel node biopsy.
The researchers used a special laboratory technique to find breast cancer cells in the lymph nodes. They found that about 16% of the women had small clumps of cancer cells (called occult metastases) in one or more of their axillary lymph nodes even though analysis of the sentinel node found no cancer cells.
The women with small clumps of cancer cells in their axillary lymph nodes had the same risk of recurrence (the cancer coming back) and overall survival whether they had sentinel node biopsy only or both sentinel and axillary node biopsy.
These results suggest that even if the sentinel node biopsy shows no cancer, there could still be individual or small clumps of cancer cells in the axillary lymph nodes. Still, doing axillary node biopsy because of that possibility generally isn't needed. Axillary node biopsy should only be done when it's clearly needed because it can make it take longer to recover from surgery and increase the risk of complications, including lymphedema, which is swelling of the soft tissues of the arm, hand, trunk, or breast.
If cancer cells are in the sentinel node, it means the cancer has spread beyond the breast. So more treatment may be needed to reduce the risk of recurrence, including:
- axillary node biopsy
- radiation therapy to the underarm lymph nodes (axillary radiation therapy)
- targeted therapy
- hormonal therapy (if the cancer is hormone-receptor-positive)
In the past, many doctors thought that axillary node biopsy made sense for many women diagnosed with early-stage breast cancer, even if the sentinel node showed no signs of cancer. This and other studies suggest axillary node biopsy is unnecessary for many women. One February 2011 study found that even when the sentinel node has cancer cells, chemotherapy and hormonal therapy given after surgery may make axillary node biopsy unnecessary for many women.
If you've been diagnosed with early-stage breast cancer and your doctor recommends axillary node biopsy as part of your treatment plan, you may want to ask your doctor about this study and why axillary node biopsy is recommended for you.
You can learn more on the Breastcancer.org Lymph Node Removal pages.
Editor's note: To make sure that women have the appropriate lymph node surgery, the American Society for Clinical Oncology released guidelines on sentinel lymph node biopsy for people diagnosed with early-stage breast cancer. The guidelines say sentinel lymph node biopsy SHOULD be offered under these circumstances:
- breast cancer in which there is more than one tumor, all of which have formed separately from one another (doctors call these multicentric tumors); these types of breast cancers are rare
- DCIS treated with mastectomy
- women who have previously had breast cancer surgery or axillary lymph node surgery
- women who have been treated before with chemotherapy or another systemic treatment (treatment before surgery is called neoadjuvant treatment)
Sentinel node biopsy SHOULD NOT be offered under these circumstances:
- the cancer is 5 cm or larger or locally advanced (the cancer has spread extensively in the breast or to the nearby lymph nodes)
- the cancer is inflammatory breast cancer
- DCIS treated with lumpectomy
- the woman is pregnant
The guidelines also say:
- Women with negative sentinel node biopsies shouldn’t have axillary node surgery.
- Women with one or two positive sentinel nodes who plan to have lumpectomy plus radiation also don’t need axillary node surgery.
- Women who have one or more positive sentinel nodes and plan to have mastectomy with no radiation should be offered axillary node surgery.