Updated article Posted 6/7/2012
Sentinel Lymph Node Biopsy for Breast Cancer: What You Need to Know
Jessica M. Bensenhaver, MD, Kathleen M. Diehl, MD and Alfred E. Chang, MD
University of Michigan Comprehensive Cancer Center
Ann Arbor, Michigan
The surgical component of breast cancer management is directed by the type of cancer, either invasive or non-invasive. Breast cancer confined within the lining of the endothelial cells along the breast duct is known as non-invasive (or in-situ) cancer. Breast cancer is described as invasive when it starts to spread beyond the breast duct, where the blood and lymph vessels lay that serve as a gateway for regional (axillary) or distant metastasis (elsewhere within the body)(FIGURE 1).
Lymph vessels drain excess fluid back into your circulation. Along the lymph vessel pathways are lymph nodes, large collections of lymph tissue that have a high concentration of white blood cells that fight infection and cancer. The lymph vessels of the breast drain most often into the axillary lymph nodes (underarm); but, they sometimes drain into the internal mammary nodes (along the sternum/ breastbone) or supraclavicular lymph nodes (above the clavicle) (FIGURE 2).
In the case of invasive breast cancer, evaluating the axillary lymph node basin to assess for nodal spread offers essential knowledge to guide both surgical and adjuvant (chemotherapy and/or radiation) cancer treatment planning. If your cancer is invasive, both breast and axillary surgery will be part of the surgical treatment. The discussion will involve the role of breast surgery for local control of the cancer, and axillary surgery for nodal staging evaluation and possibly regional control.
Sentinel Lymph Node Biopsy:
Historically, invasive breast cancer required an axillary lymph node dissection (ALND) in order to see if the cancer had spread to the lymph nodes. Today, sentinel lymph node biopsy (SLNB) is used to assess for axillary nodal spread without subjecting the patient to a full ALND. Experience has shown us that the lymph ducts of the breast usually drain to one lymph node first, before draining to the remaining underarm nodes. This first lymph node is called the sentinel lymph node (SLN), the one that would be first to show that that cancer has spread.
Lymph node mapping is the process through which the sentinel node is identified and made available for biopsy. Mapping is accomplished either by a weak radioactive dye (technetium-labeled sulfur colloid) that can be measured by a hand held probe, or by a blue day (isosulfan blue or methylene blue) that stains the lymph tissue a bright blue color. Most surgeons use a combination of the radioactive and blue dye.
The SLNB procedure has both surgical and diagnostic advantages. In comparison to ALND for axillary nodal staging evaluation, the procedure can be performed in an outpatient setting, there is no need for a drain, there is no need for physical therapy, and the recuperation is much faster with most patients doing regular activities within a few days and back to exercising using the arm within a few weeks. The incision is well-healed within a few weeks. From a diagnostic perrospective, a SLNB can lead to a more accurate assessment of whether the cancer has spread to the nodes. In a traditional ALND, the pathologist receives at least 10 lymph nodes without an identified sentinel node. The pathologist makes one cut in each node to look for cancer. In the setting of SLNB, only one node, or at most a few nodes, are evaluated giving the pathologist the opportunity to make many cuts through the sentinel node to look for cancer. A negative sentinel lymph node(s) indicates a >95% chance that the remaining lymph nodes in the axilla are also cancer free; therefore, eliminating the need for a full ALND and consequently avoiding the risks and long terms complications associated with ALND.
What to Expect:
The first step involved in SLNB is lymphatic mapping. Either the evening before or morning of surgery, the patient will present to nuclear medicine where the radioactive dye used for the procedure is injected. The injections are performed either peri-tumoral (around the tumor) or peri-areolar (around the nipple areolar complex). After a few hours, lymphosintigraphy pictures are taken in the nuclear medicine department to show the pathway the dye takes as it leaves the breast. (FIGURE 3) This serves as a guide for your surgeon to aid identification of the sentinel node. Then, once in the operating room at the initiation of the procedure, the surgeon will inject the blue dye. An incision is made in the underarm at the area of the axillary lymph tissue. A hand-held sterile probe is used to measure levels of radioactive dye within the axillary fat pad. (FIGURE 4) The lymph nodes that have taken up the radioactive dye, or are stained with blue dye are removed. Usually one to three nodes are identified as sentinel nodes and removed. They are then sent to the pathologist who looks at them under a microscope to see if they contain cancer. If there is no cancer, the incision is closed.
The sentinel node biopsy can be done in combination with a lumpectomy, or a mastectomy. No drain is needed, no physical therapy is needed, and it can be performed on an outpatient basis. SLNB is successful in >90% of those patients whom we thing are good candidates for the procedure. If the procedure is unsuccessful in identifying the sentinel node, a full ALND is done.
Positive Sentinel Node:
Current surgical recommendations upon identification of positive sentinel node(s) are currently shifting. Traditionally, in the face of positive sentinel node(s), it was recommended that the patient undergo completion ALND to remove the remaining lymph nodes which could contain cancer. However, because the majority of patients with node positive breast cancer receive systemic chemotherapy and because there has been a significant increase in the diagnosis of early stage breast cancer with limited nodal disease, the question arises regarding the need for axillary lymph node dissection for microscopic disease. Recently, the ACOSOG Z0011 trial has addressed the role of completion axillary lymph node dissection in patients with early stage breast cancer who underwent lumpectomy as local surgical therapy for their cancer with limited positive axillary nodes. This study looked at patients with breast tumors less than 5 centimeters and less than 3 positive sentinel nodes. The patients were then divided into two groups: one that underwent ALND, the other did not. All patients completed whole breast radiation as part of their breast conservation therapy and the majority also completed chemotherapy. Both groups were carefully watched and at 5-years follow-up, there was no survival benefit seen in those patients who did not undergo ALND. Unfortunately, this trial was not able to enroll the anticipated number of patients needed to establish definitive information and the vast majority of patients had very favorable tumor characteristics; however, the study results have definitely given insight to this controversial topic to which all surgeons are adapting as they see appropriate for each patient. Talk to your surgeon about the role of ALND in your specific case. Early cancers with favorable characteristic and limited axillary disease should be considered as potential cases to forego the ALND. For bulky axillary disease, locally advanced disease, high grade aggressive tumors, or those patients undergoing mastectomy, ALND is still the favored approach toward axillary management of the disease in order to not risk undertreating your breast cancer.
Who Shouldn’t Undergo Sentinel Node Biopsy:
The sentinel lymph node biopsy procedure cannot be performed in all cases of invasive breast cancer. This includes patients with clinically positive node disease (bulky nodes), those for whom the dye does not map, or those with previously established axillary disease or who have had previous surgery in the axilla. Patients with occult malignancy (unable to find the primary breast tumor) that present with axillary metastasis are candidates for directed axillary node dissection. Also, any patient that has previously undergone mastectomy cannot have a sentinel node biopsy because there is no way to inject the dye and identify the node. Additionally, some patients do not map after injection of the dyes. These patients usually include those with expected breast changes after previous radiation therapy and/or breast or axillary surgery. Although having a history of any of these previous therapies is not a complete contraindication to attempt sentinel lymph node biopsy, it must be accepted that these patients are at an increased risk to not map successfully and that complete axillary lymph node dissection would thus be indicated. Some patients have a higher incidence of nodal spread even without obvious axillary disease. These patients include those with large tumors (greater then 5cm) or those with multifocal disease. Therefore, if sentinel node biopsy is attempted and there is any concern with accuracy of the mapping, then complete axillary lymph node dissection is indicated. Lastly, preoperative confirmation of axillary disease can be accomplished through axillary node fine needle aspiration or core needle biopsy, even in clinically node negative patients. A fine needle aspiration (FNA) is the aspiration of a few cells through a needle inserted into the lymph node. A core needle biopsy (CNB) is the removal of a slice of tissue through the needle inserted into the lymph node. As stated before, there has been a significant increase in the incidence of early stage breast cancer often with limited axillary disease, if any, that is difficult to discern by physical exam. Axillary ultrasound has become a popular component of axillary evaluation in such patients as an adjunct to the physical exam. If an abnormal node(s) is identified, then these patients can undergo ultrasound guided needle biopsy of the node (either FNA or CNB). If a needle biopsy is found positive for nodal metastasis, the patient is then directed to forego SNLB for ALND.
Axillary Lymph Node Dissection:
An axillary lymph node dissection requires an incision under the arm, usually extended from the SLNB incision or from the lateral portion of the mastectomy incision. The bulk of the lymph node tissue that drains the breast is removed and sent to the laboratory. A pathologist then looks at the lymph nodes under a microscope and determines if any of the nodes contain cancer. On average, approximately 10 to 15 nodes are removed. (The number of lymph nodes in the axilla varies from person to person therefore we cannot predict ahead of the operation how many nodes will be removed.) The remaining tissues underneath the arm tend to “leak” lymph fluid after the nodes are removed. Therefore, a drain is usually placed at the time of surgery through a separate skin incision, attached to an output collection bulb and is usually left in place for 2-3 weeks after the operation. At home, physical therapy exercises are encouraged to maintain strength and flexibility in the shoulder as it heals. Once the drain output diminishes, the drain can be removed in clinic. Approximately 12-24% of patients who undergo an ALND experience chronic problems related to the dissection such as arm swelling (lymphedema) or pain and/or discomfort in the area of the dissection. Almost all women have some residual numbness under the inside of the arm.
Who Should Do the Procedure:
Sentinel lymph node biopsy should be done by an experienced, qualified breast surgeon. Initial studies showed that most surgeons need to do 20-30 sentinel node procedures before obtaining accurate results. More recent studies, however, show that for surgeons using a well standardized technique, achieving accurate results occurs in a much shorter time period with most failed results occurring in the first few cases. This experience usually occurs during an accredited residency or fellowship at an institution that does a large number these cases. It is important, to ask your surgeon about their experience.
Invasive breast cancer can spread through the lymph ducts and blood vessels to other areas of the body. The sentinel lymph node is the first lymph node(s) that the lymph ducts drain into. Whether or not the cancer has spread to the sentinel lymph node helps to indicate whether the cancer has started to spread beyond the breast. Sentinel node biopsy identifies this node and allows only this lymph node to be removed and checked for cancer. Removing just the sentinel node(s) can allow breast cancer patients to avoid many of the complications and side effects associated with a traditional axillary lymph node dissection. Because the Z0011 study focused on early cancer treated with breast conservation in patients with limited axillary disease, the recommendation for avoiding ALND is limited to patients that fit these criteria. ALND is still recommended in patients with known axillary disease confirmed with preoperative FNA or core biopsy and those undergoing mastectomy. Patients with invasive breast cancer should discuss sentinel lymph node biopsy with their surgeon and the role of ALND in the face of positive results. Finally, although it occurs more commonly after ALND, lymphedema can also occur after SLNB. Because early treatment is very successful, patients should discuss recognition of lymphedema with their surgeon and be aware of who to contact if they suspect symptoms.
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