There has been a growing interest in methods to reduce the incidence of lymphedema in patients undergoing lymph node removal. The lymph nodes are removed as part of the treatment for breast cancer. Cells from cancers of the breast will break off from the cancer and migrate through the lymphatic channels to the regional lymph nodes. As a result, removal of the lymph nodes serves two functions. First, the nodes can be studied under the microscope. If there are no cancer cells in the lymph nodes, the risk of recurrence of the cancer is much lower than if there is metastatic cancer in the lymph nodes and less aggressive treatment is required to control the cancer. Patients with cancer in their lymph nodes will require additional treatment and their chance of recurrence of the cancer is higher. Second, if the cancer does involve the lymph nodes, removal of as much of the cancer as possible is important prior to further treatment with radiation or chemotherapy.
The sentinel node biopsy is an attempt to reduce the extent of axillary dissection required to determine if there is cancer in the nodes. The lymph nodes are small structures, about the size of a small pea, located throughout the body. They serve as immunological filters to protect the body. Cancer cells from the breast will migrate to the lymph nodes in the axilla. There are over 50 small lymph nodes in the axilla. To determine whether there is cancer in the lymph nodes, a sample of 5 to 10 of these nodes are removed surgically and studied under the microscope.
Instead of removing 5 to 10 nodes, the sentinel node biopsy removes the one node most likely to have cancer cells. To do this, a new technique has been developed that uses a combination of a radioactive tracer and a color dye. The dye is injected around the tumor or into the biopsy cavity. The dye will migrate through the lymphatic channels to the regional lymph nodes drained by the cancer. The specific node most likely to be involved with cancer is then identified and removed for microscopic analysis.
The important question for the well being of the cancer patient is whether biopsy of one node is sufficient to insure that no cancer cells are missed. It would be a tragedy to allow a woman to die needlessly because an inadequate biopsy resulted in ineffective treatment.
A recent study presented at the San Antonio Breast Cancer meetings suggests that the sentinel node biopsy is may be nearly as accurate as an axillary dissection. 224 sentinel node biopsies were performed. In 54 cases there was evidence of cancer. The usual axillary dissection was performed in the remaining cases and additional cancer was found in the lymph nodes in 1 case. In this case, the cancer appeared to skip the sentinel node and was found in adjacent nodes.
The results of this study indicate that in very skilled hands the sentinel node biopsy can be nearly as effective as an axillary dissection. Still, one cancer was missed and could result in ineffective treatment if the additional axillary dissection was not performed. These finding; however, are very exciting. With further refinement that this test may be as good as an axillary dissection and may lead to the elimination of axillary dissection for the diagnosis of metastatic cancer. Our goal is a non-invasive test that is even more predictive that axillary dissection.
The sentinel node biopsy is still a new technique and few facilities have the ability to perform sentinel node biopsies and insure accuracy of their findings. In addition, we do yet not know if this will reduce the incidence of lymphedema. We are hopeful, however, that more limited and precise surgery will decrease the incidence of lymphedema.