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New Lymphatic Mapping May Avoid Many Axillary Dissections

New Lymphatic Mapping May Avoid Many Axillary Dissections

A new minimally invasive surgery can provide better diagnosis and staging of cancer, according to a presentation at the 48th Annual Cancer Symposium of the Society of Surgical Oncology (SSO), where doctors debated surgical techniques for lymph node mapping to detect metastases.

David M. Ota, MD, of the University of Missouri Ellis Fischel Cancer Center, who moderated the discussion, described these new lymphatic mapping techniques as the "new trend" that provides "better ways to treat patients using minimal access."

Armando E. Giuliano, MD, of the John Wayne Cancer Institute, described a technique of axillary node mapping for breast cancer metastases using a blue dye which can assist surgeons in localizing and detecting the sentinel lymph node for biopsy. The new mapping technique is based on the concept that lymph drainage, including metastases, will lead to the sentinel lymph node. If the sentinel lymph nodes can be resected, they can be studied for metastases, which will help doctors to determine the staging and extent of metastases, Dr. Giuliano said.

The Cost of Axillary Dissection

The new method has been developed in response to the problems associated with total axillary dissection, such as morbidity and the expense of the procedure. Sentinel lymphadenectomy using axillary node mapping techniques may prove to be sufficiently accurate and more cost effective than total axillary lymphadenectomy, he said.

The procedure involves the injection of a blue dye about 5 minutes prior to incision. The sentinel node is visualized by following the blue-stained lymphatic vessels. The sentinel node is excised as a separate specimen before the resection of the remaining axillary nodes. The pathologist can then examine the frozen section, and immunohistochemical staining for cytokeratin can "add significantly to the evaluation of the sentinel node," Dr. Giuliano said.

In a comparison of patients who had total axillary lymph node dissection and patients who underwent sentinel lymph node dissection prior to axillary lymph node dissection, the number of patients with positive nodes was increased dramatically, illustrating the increased diagnostic capability of the new procedure. In addition, the ability to detect micrometastases was enhanced threefold by the sentinel lymph node dissection, Dr. Giuliano said.

"Sentinel lymphadenectomy enhances staging compared to total lymphadenectomy, partly because the pathologist can perform better analysis with fewer nodes to examine," he noted.

The false-negative rate of the sentinel lymphadenectomy can be decreased, depending on factors such as the extent of dissection, the plane of nodal dissection, the number of sections examined, immunohistochemical staining, and the skill of the pathologist.

The sentinel lymphadenectomy also enables the identification of skip metastases, Dr. Giuliano said.

However, some of the problems associated with sentinel lymphadenectomy are just being worked through. Occasionally, the level II or level III nodes can be missed by the surgeon. In patients with a large axillary tumor burden, it is more difficult to identify the sentinel lymph node. The skill of the surgeon is also critical in successfully identifying the sentinel node.

Other problems with the dye visualization method include variability, time of uptake, and edema. Also, it does take some time to master the art of identifying the sentinel node, Dr. Giuliano emphasized. Most of the errors in detecting metastases occurred in the first 75 cases. Currently he is able to identify the sentinel node in 80% to 85% of patients. The likelihood that the sentinel node contains metastases as compared to other nodes is highly significant (P < .00001).

A Second Method: Gamma Probe

Other doctors have used an alternative mapping procedure by using a radiolabeled gamma probe instead of the blue dye. The gamma probe is injected preoperatively, and the radioactivity is detected with a gamma counter prior to incision. Dr. Giuliano believes that the dye method is superior to gamma probe-guided resection, because he is not convinced that the "ease of detection with the radiolabeled probe justifies its cost."

However, Merrick R. Ross, MD, of the M.D. Anderson Cancer Center believes that using the dye in conjunction with a radiolabeled technetium-99 probe can increase the accuracy of inguinal node mapping for melanoma. "The two methods complement each other," Dr. Ross said. The gamma probe has additional value, because the removal of all sentinel nodes can be documented, he said. The nodal basin can be rescanned, and any nodes that may have been missed can be detected.

Although the use of these mapping technique are not yet a standard of care, both Drs. Giuliano and Ross believe that sentinel node mapping, when done accurately, may be all that is needed. It substantially reduces the hospital stay of the patient, and may be performed with local anesthesia as an outpatient proceedure.

 
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