Understanding Sentinel Node Biopsy

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Title: Understanding Sentinel Node Biopsy
Author: Kathleen M Diehl, MD and Alfred E. Chang, MD
m.a.d. Patients
Publisher: Division of Surgical Oncology, University of Michigan Comprehensive Cancer Center

A sentinel lymph node biopsy is a relatively new
technique. This was developed as a test to determine if
breast cancer has spread to the lymph ducts or lymph
nodes in the axilla without having to do a traditional
axillary lymph node dissection. Experience has shown
that the lymph ducts of the breast usually drain to one
lymph node first, before draining through the rest of the
lymph nodes underneath the arm. That first lymph node
is called the sentinel lymph node. That is the lymph
node that helps sound the warning that the cancer has
spread. Lymph node mapping helps identify that lymph
node, and a sentinel lymph node biopsy removes only
that lymph node. The sentinel lymph node is identified
in one of two ways, either by a weak radioactive dye
(technetium-labeled sulfur colloid) that can be measured
by a hand held probe, or by a blue dye (isosulfan blue)
that stains the lymph tissue a bright blue so it can be
seen. Most breast cancer surgeons use a combination of
both dyes.

The advantages to the sentinel lymph node procedure
are many. In addition to being less invasive and
capable of being performed on an outpatient basis, a
sentinel lymph node biopsy can lead to a more accurate
assessment of whether the cancer has spread to the
lymph nodes. In a traditional axillary dissection, the
pathologist examines at least 10 lymph nodes or more;
there is no way of telling which one is the sentinel
lymph node. So the pathologist makes one cut in each
lymph node and looks for cancer. When the pathologist
receives only one, or a few, lymph nodes from a
sentinel lymph node procedure, he or she can make
many cuts through that lymph 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, there is no need
to undergo a full axillary lymph node dissection, or to
risk the long term complications and side effects from
an axillary dissection.


Who Should Not Undergo Sentinel Node Biopsy

Unfortunately, the sentinel lymph node biopsy procedure
can't be performed on everyone with an invasive breast
cancer. People who have had radiation therapy or
surgery in their breast or axilla should not undergo the
technique, as changes in the breast and axilla from the
radiation therapy or surgery may make the results
inaccurate. People who have enlarged lymph nodes
underneath their arm, or people who known already
to have breast cancer metastatic to their axillary lymph
nodes should undergo a traditional axillary lymph node
dissection. People who already have had a mastectomy
can't undergo the procedure because there is no
accurate way to inject the dye to identify the lymph
node. People with large tumors (greater then 5cm) have
a higher incidence of lymph node spread of their cancer,
and may be better served by a traditional lymph node
dissection. They should discuss this with their surgeon.
People, in whom it will be difficult to accurately inject
the dye, would likely be better served by a full axillary
lymph node dissection. This includes those people in
whom the physicians are unable to find the primary
breast tumor (an "occult" malignancy), and people in
whom the tumor is dispersed through more then one
area of the breast (a multifocal tumor).

In-Depth Article on Breast Cancer Detection & Treatment...
http://www.emedicine.com/med/topic2808.htm


Qualification to Perform Sentinel Node Biopsy

One of the factors that influences the results obtained
with the procedure, is the qualification of the breast
surgeon doing the procedure. Initial studies have shown
that most surgeons need to do 20-30 sentinel lymph
node biopsy procedures before obtaining accurate
results using the technique. Surgeons can perform these
cases during an accredited residency or fellowship at an
institution that does a large number of these cases a
year. Alternatively, surgeons attend a conference to
learn the technique, then acquire these 20-30 cases as
part of a training protocol. During the training period,
the surgeon will perform the sentinel lymph node
biopsy, and then complete a full axillary lymph node
dissection in the same operation. After obtaining the
pathology results, the surgeon can then determine if the
sentinel lymph node was correctly identified. In
addition, the surgeon can determine that the cancer was
found in the sentinel node, and not in the lymph nodes
that would otherwise have been left behind (false
negative rate). After a surgeon has done 20-30 cases in
which the sentinel lymph node is identified in >90% of
the cases, and the false negative rate is less then 5%,
then the surgeon "goes off protocol", and does sentinel
lymph node biopsies without a full axillary dissection.
Until the surgeon has completed a large number of
cases, and determined her/his accuracy for doing the
technique, any cases done "off protocol" may
inaccurately determine if there has been spread of
cancer to the axillary lymph nodes.

Excellent Article on Sentinel Node Biopsy Basics...
http://www.cancernews.com/data/Article/202.asp

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