Dr. Susan Love Research Foundation | Axillary Lymph Node Dissection: Is it Necessary?

When a woman has a lumpectomy or mastectomy, her surgeon will also look to see if there are affected lymph nodes under the arm (axilla). For decades this was done with a procedure called an axillary lymph node dissection, which involves removing about 10-15 of the 30–60 lymph nodes under the arm. After they are removed, the nodes are examined under a microscope. If the pathologist identifies cancer cells it means that there is a greater statistical risk of there being microscopic cells elsewhere in the body and therefore a higher risk of a recurrence. If no cancer cells are seen, the risk is lower that there are microscopic cells elsewhere in the body. This estimate of risk is used to decide on whether and how much treatment in addition to surgery is needed.

Now, women are just as likely to have a procedure called a sentinel node biopsy, which identifies the first nodes that drain the area of the tumor and therefore are the node or nodes most likely to have cancer cells. Because a positive sentinel node suggests that there will be other positive nodes in the axilla, the current standard of care is for women who have a positive (cancerous) sentinel node to go on to have a full lymph node dissection. But findings from a study presented at the American Society of Clinical Oncology (ASCO) Annual Meeting in June could change this.

The Phase III study was conducted at the John Wayne Cancer Institute in Santa Monica, California. It enrolled 991 women who were scheduled to have a lumpectomy followed by radiation and whose sentinel lymph node biopsy identified a positive sentinel node. The women were randomly assigned to one of two groups. One group went on to have an axillary node dissection with removal of 10 or more additional lymph nodes (the standard of care). The other group had no additional lymph nodes removed. Both groups of women had radiation therapy to their breasts and axilla. The researchers then followed the women to see whether those who had limited surgery had a greater chance of local recurrence.

After six years of follow up, the researchers found that, as a group, the women who had no additional surgery did the same as the women who had gone on to have the additional lymph nodes removed. Specifically, the five-year overall survival rate in patients undergoing axillary lymph node dissection was 91.9 percent compared to 92.5 percent for those who only had a sentinel node biopsy. Disease-free survival was 82.2 percent among the women who had the axillary lymph node dissection compared with 83.8 percent for the women who did not. The rate of local/regional recurrence was 4.3 percent among women who had an axillary lymph node dissection and 3.4 percent among those who had only the sentinel node biopsy. None of these differences was statistically significant.

Currently, many surgeons routinely do an axillary node dissection in women who have a sentinel node that tests positive for cancer cells. While these results are very encouraging not enough women were enrolled in the study to make it definitive. However, it is the largest study of this type done to date, and it's important because it suggests that this additional surgery may not be necessary. And not doing the additional surgery would mean there were fewer women who were at risk of going on to develop lymphedema, numbness in the arm, and other side effects.

Is an axillary lymph node dissection ever necessary? It may still be needed if a woman has nodes that are palpable, a very large cancer, or a lymph node that is obviously positive. Nonetheless, this is one more study showing that more is not always better in treating breast cancer.