New Lymphatic Mapping May Avoid Many Axillary Dissections

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

David M. Ota, MD, of the University of Missouri Ellis FischelCancer Center, who moderated the discussion, described these newlymphatic mapping techniques as the "new trend" thatprovides "better ways to treat patients using minimal access."

Armando E. Giuliano, MD, of the John Wayne Cancer Institute, describeda technique of axillary node mapping for breast cancer metastasesusing a blue dye which can assist surgeons in localizing and detectingthe sentinel lymph node for biopsy. The new mapping techniqueis based on the concept that lymph drainage, including metastases,will lead to the sentinel lymph node. If the sentinel lymph nodescan be resected, they can be studied for metastases, which willhelp 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 problemsassociated with total axillary dissection, such as morbidity andthe expense of the procedure. Sentinel lymphadenectomy using axillarynode mapping techniques may prove to be sufficiently accurateand more cost effective than total axillary lymphadenectomy, hesaid.

The procedure involves the injection of a blue dye about 5 minutesprior to incision. The sentinel node is visualized by followingthe blue-stained lymphatic vessels. The sentinel node is excisedas a separate specimen before the resection of the remaining axillarynodes. The pathologist can then examine the frozen section, andimmunohistochemical staining for cytokeratin can "add significantlyto the evaluation of the sentinel node," Dr. Giuliano said.

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

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

The false-negative rate of the sentinel lymphadenectomy can bedecreased, 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 ofskip metastases, Dr. Giuliano said.

However, some of the problems associated with sentinel lymphadenectomyare just being worked through. Occasionally, the level II or levelIII nodes can be missed by the surgeon. In patients with a largeaxillary tumor burden, it is more difficult to identify the sentinellymph node. The skill of the surgeon is also critical in successfullyidentifying the sentinel node.

Other problems with the dye visualization method include variability,time of uptake, and edema. Also, it does take some time to masterthe art of identifying the sentinel node, Dr. Giuliano emphasized.Most of the errors in detecting metastases occurred in the first75 cases. Currently he is able to identify the sentinel node in80% to 85% of patients. The likelihood that the sentinel nodecontains 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 usinga radiolabeled gamma probe instead of the blue dye. The gammaprobe is injected preoperatively, and the radioactivity is detectedwith a gamma counter prior to incision. Dr. Giuliano believesthat the dye method is superior to gamma probe-guided resection,because he is not convinced that the "ease of detection withthe radiolabeled probe justifies its cost."

However, Merrick R. Ross, MD, of the M.D. Anderson Cancer Centerbelieves that using the dye in conjunction with a radiolabeledtechnetium-99 probe can increase the accuracy of inguinal nodemapping for melanoma. "The two methods complement each other,"Dr. Ross said. The gamma probe has additional value, because theremoval of all sentinel nodes can be documented, he said. Thenodal basin can be rescanned, and any nodes that may have beenmissed can be detected.

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