According to a recent publication in the Journal of the National Cancer Institute, sentinel node biopsies are becoming increasingly utilized as a standard approach in the management of localized breast cancer in some major academic centers in the United States.
Localized breast cancer refers to cancer that has not spread outside the breast, except for the possible spread to axillary (under the arm) lymph nodes. The presence or absence of cancer cells in axillary (under the arm) lymph nodes in early-stage breast cancer 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 in the body, 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. Axillary node dissection is still considered the standard of care in the United States; however, 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.
Recently, researchers from 5 major academic centers have reported that SNB is becoming the standard practice for the treatment of early stage breast cancer at their institutions. Although SNB is still considered an investigative procedure, all phase II studies to date have shown that sentinel node biopsy accurately predicts the status of metastatic spread of cancer to axillary nodes and can be effectively used to plan appropriate therapy. Larger clinical trials are currently being performed to determine if there are any differences in recurrence rates or survival when this technique is used. The authors of the current study indicate that from July 1997 to December 2000, SNB procedures have increased 2.3 fold at each 6-month interval. In patients diagnosed with stage I breast cancer, the frequency of SNB has risen from 8% to 58% during that time period. The authors commented that the results of utilizing SNB as a standard approach prior to results from the last phase of clinical trials evaluating this issue are unknown.
Patients with early-stage breast cancer may wish to discuss the risks and benefits of SNB with their physician, as well as the experience of the physician planning to perform SNB, should this be the procedure of choice.
Reference: Edge SB, Niland JC, Bookman MA, et al. Emergence of sentinel node biopsy in breast cancer as standard-of care in academic comprehensive cancer centers. Journal of the National Cancer Institute. 2003;95:1514-1521.