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
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.