Sentinel
Node Biopsy Becoming Standard Approach for Localized Breast
Cancer
According to a recent publication in the Journal of the National
Cancer Institute, sentinel node biopsies are becoming increasingly
utilized as a standard approach in the management of localized
breast cancer in some major academic centers in the United
States.
Localized breast cancer refers to cancer that has not spread
outside the breast, except for the possible spread to axillary
(under the arm) lymph nodes. The presence or absence of cancer
cells in axillary (under the arm) lymph nodes in early-stage
breast cancer is an essential factor in defining optimal treatment
strategies following surgery. Women who have cancer cells
present in their axillary lymph nodes are thought to have
cancer that has spread in the body, and therefore require
adjuvant systemic (full-body) therapy. Conversely, women without
cancer cells in their axillary lymph nodes are thought to
have only localized breast cancer and may require less aggressive
adjuvant therapy and observation.
For over 30 years, the standard of practice for breast cancer
staging has included the removal of axillary (under the arm)
lymph nodes to aid in determining the spread of cancer in
the body. If cancer spreads from its site of origin, it is
thought to spread first to the lymph nodes that initially
collect the excess lymph fluid from that area (sentinel lymph
nodes). Standard staging procedures had included the removal
of axillary lymph nodes during surgery, referred to as axillary
dissection. These nodes were then tested in the laboratory
to determine if they contained breast cancer cells. Axillary
node dissection is still considered the standard of care in
the United States; however, a different strategy to test for
the presence of cancer cells in axillary lymph nodes, called
sentinel node biopsy, is gaining momentum in the clinical
setting as results from more clinical trials are indicating
that sentinel node biopsy is effective.
The removal of axillary lymph nodes (approximately 10-25
nodes) is associated with chronic side effects including pain,
infection, limited shoulder motion, numbness and lymphedema
(swelling of the arm due to an accumulation of lymph fluid).
Since these complications can become debilitating, the strategy
of sentinel lymph node dissection continues to be refined
and evaluated. This strategy incorporates the removal of only
the sentinel lymph node(s) for biopsy (SNB) to determine the
extent of cancer spread. The sentinel lymph node(s) (SLN)
receives initial drainage from the cancer, and thus has the
highest probability of containing cancer cells if the cancer
has spread. Therefore, the removal of other axillary lymph
nodes may be unnecessary if the SNB is negative. If accurate,
this practice could eliminate the need for standard axillary
node dissection and its complications.
The precision in correctly identifying the SLN is imperative
in order for this procedure to provide accurate results. Currently,
there are two methods that can be used individually or together:
1) injections of blue dye in the area immediately encompassing
the cancer, 2) injections of a radioactive substance in the
area immediately encompassing the cancer. The injections are
administered prior to surgery. During surgery, the surgeon
identifies the node(s) containing either the blue dye (through
direct visualization) or the radioactive substance (through
a hand-held probe that detects radioactivity), indicating
the collection of drainage from the cancer. The node(s) that
collects the injected substances is determined to be the SLN
and is subsequently removed for a SNB. Furthermore, the accuracy
in identifying a SLN depends largely on the skills of the
physician, with more practiced physicians resulting in improved
accuracy.
Recently, researchers from 5 major academic centers have
reported that SNB is becoming the standard practice for the
treatment of early stage breast cancer at their institutions.
Although SNB is still considered an investigative procedure,
all phase II studies to date have shown that sentinel node
biopsy accurately predicts the status of metastatic spread
of cancer to axillary nodes and can be effectively used to
plan appropriate therapy. Larger clinical trials are currently
being performed to determine if there are any differences
in recurrence rates or survival when this technique is used.
The authors of the current study indicate that from July 1997
to December 2000, SNB procedures have increased 2.3 fold at
each 6-month interval. In patients diagnosed with stage I
breast cancer, the frequency of SNB has risen from 8% to 58%
during that time period. The authors commented that the results
of utilizing SNB as a standard approach prior to results from
the last phase of clinical trials evaluating this issue are
unknown.
Patients with early-stage breast cancer may wish to discuss
the risks and benefits of SNB with their physician, as well
as the experience of the physician planning to perform SNB,
should this be the procedure of choice.
Reference: Edge SB, Niland JC, Bookman MA, et al. Emergence
of sentinel node biopsy in breast cancer as standard-of care
in academic comprehensive cancer centers. Journal of the National
Cancer Institute. 2003;95:1514-1521.
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