Hormone Sentinel Node Biopsy as Effective with Fewer Side Effects as Axillary Dissection in Breast Cancer
According to results published in The New England Journal of Medicine, the largest analysis to date indicates a sentinel node biopsy is just as effective as standard axillary node dissection, with fewer associated side effects, in patients with early-stage breast cancer.
The presence or absence of cancer cells in axillary (under the arm) lymph nodes is an essential factor in defining optimal treatment strategies following surgery. Women who have cancer cells present in their axillary lymph nodes are thought to have cancer that has spread, and therefore require adjuvant systemic (full-body) therapy. Conversely, women without cancer cells in their axillary lymph nodes are thought to have only localized breast cancer and may require less aggressive adjuvant therapy and observation.
For over 30 years, the standard of practice for breast cancer staging has included the removal of axillary (under the arm) lymph nodes to aid in determining the spread of cancer in the body. If cancer spreads from its site of origin, it is thought to spread first to the lymph nodes that initially collect the excess lymph fluid from that area (sentinel lymph nodes). Standard staging procedures had included the removal of axillary lymph nodes during surgery, referred to as axillary dissection. These nodes were then tested in the laboratory to determine if they contained breast cancer cells. Although axillary node dissection is still commonly used today, a different strategy to test for the presence of cancer cells in axillary lymph nodes, called sentinel node biopsy, is gaining momentum in the clinical setting as results from more clinical trials are indicating that sentinel node biopsy is effective.
The removal of axillary lymph nodes (approximately 10-25 nodes) is associated with chronic side effects including pain, infection, limited shoulder motion, numbness and lymphedema (swelling of the arm due to an accumulation of lymph fluid). Since these complications can become debilitating, the strategy of sentinel lymph node dissection continues to be refined and evaluated. This strategy incorporates the removal of only the sentinel lymph node(s) for biopsy (SNB) to determine the extent of cancer spread. The sentinel lymph node(s) (SLN) receives initial drainage from the cancer, and thus has the highest probability of containing cancer cells if the cancer has spread. Therefore, the removal of other axillary lymph nodes may be unnecessary if the SNB is negative. If accurate, this practice could eliminate the need for standard axillary node dissection and its complications.
The precision in correctly identifying the SLN is imperative in order for this procedure to provide accurate results. Currently, there are two methods that can be used individually or together: 1) injections of blue dye in the area immediately encompassing the cancer, 2) injections of a radioactive substance in the area immediately encompassing the cancer. The injections are administered prior to surgery. During surgery, the surgeon identifies the node(s) containing either the blue dye (through direct visualization) or the radioactive substance (through a hand-held probe that detects radioactivity), indicating the collection of drainage from the cancer. The node(s) that collects the injected substances is determined to be the SLN and is subsequently removed for a SNB. Furthermore, the accuracy in identifying a SLN depends largely on the skills of the physician, with more practiced physicians resulting in improved accuracy.
Researchers from Italy recently conducted a clinical trial to further evaluate the effectiveness of sentinel-node biopsy in patients with early breast cancer. This trial involved 516 patients with breast cancer that was no greater than 2 centimeters in diameter. The patients were divided into two groups: one group received SNB followed by axillary node dissection (axillary dissection group), and the other group received SNB followed by axillary node dissection only if cancer cells were present in the sentinel node (sentinel node group). In the axillary dissection group, the overall accuracy of SNB was nearly 97%. The number of sentinel nodes identified in each group were similar, as well as the number of patients identified with positive sentinel nodes (33% in each group). Nearly 4 years following therapy, cancer recurrences, spread of cancer or a possible second breast cancer occurred in 10 patients in the sentinel node group, compared with 15 patients in the axillary dissection group. No patients who were treated only with SNB have developed cancer spread to the axillary lymph nodes as determined by physical examination. Patients receiving SNB only, suffered from less pain, numbness, arm swelling and had greater arm movement than those undergoing axillary node dissection.
The researchers concluded that SNB appears just as effective in determining cancer spread to axillary lymph nodes as axillary dissection, and results in fewer side effects in patients with breast cancer that is 2 cm or smaller in diameter. Patients with early breast cancer may wish to speak with their physician about the risks and benefits of SNB compared to axillary dissection. If SNB is considered, patients should inquire as to the number of SNB procedures performed at their institution.
Reference: Veronesi U, Paganelli G, Viale G, et al. A randomized comparison of sentinel-node biopsy with routine axillary dissection in breast cancer. The New England Journal of Medicine. 2003;349:546-553.