ORLANDOBoth dye and radioactive tracer are required for finding
sentinel lymph nodes most accurately in patients with operable breast
cancer, but small intradermal injections of the tracer can be used
instead of intraparenchymal tracer injections, researchers from
Memorial Sloan-Kettering Cancer Center reported at the Society of
Surgical Oncologys Annual Cancer Symposium.
A single-site, low-volume, intradermal injection of radioactive
tracer is easier to perform, requires less radiocolloid, and could
potentially reduce costs, David C. Linehan, MD, said at the
Sentinel lymph nodes can be identified by dye, by radioisotopes, and
by a combination of the two. Sentinel lymph node biopsy is based on
the concept that specific areas drain first to specific lymph nodes
within the regional basin via an organized system of afferent
lymphatic channels. A dye such as isosulfan blue injected at the
tumor site permits identification of the first draining or sentinel
node because it is the first one to take up the blue color.
Histologically, the sentinel lymph node reflects the status of the
rest of the regional drainage basin, and a negative sentinel node can
spare the patient the morbidity and expense of an unnecessary
axillary dissection. Injection of radioactive tracers, such as
technetium 99mTc sulfur colloid, is also used to identify the
sentinel node, based on the fact that the radiolabeled colloid is
actively incorporated into the draining sentinel node.
Dr. Linehan reported that experience at Sloan-Kettering in more than
1,000 procedures suggests that both dye and radiocolloid must be used
to obtain the greatest accuracy. If only blue dye were used, we
would have missed 20% of sentinel nodes. If isotope alone were used,
we would have missed 15%. Where dye failed, 13% were rescued by
isotope. Where isotope failed, 8% were rescued by dye, he said.
However, clinicians are using many variations in technique for
finding the sentinel node. Dr. Linehan and his colleagues were
intrigued by reports that intradermal injection of the radiocolloid
could be used instead of the more difficult intraparenchymal
They examined these two approaches in a study of 200 consecutive
patients with T1 or T2 breast tumors who had sentinel lymph node
biopsies; the patients were treated by a single surgeon. Half had
intraparenchymal dye injection plus intraparenchymal radiocolloid,
and half had intraparenchymal dye plus intradermal radiocolloid.
Dr. Linehan said that the study was undertaken to answer the
Which injection site (intradermal or intraparenchymal) optimizes
sentinel lymph node localization?
If intradermal injection is as good as or better than
intraparenchymal injection, do dermal and parenchymal lymphatics
drain to the same sentinel nodes?
Would this procedure be as accurate for staging the clinically
negative axilla if intradermal injection was used?
Study endpoints included successful sentinel node localization by
lymphoscin-tigraphy, successful sentinel node localization at the
time of operation, and blue dye-isotope concordance (uptake of dye
and isotope by the same sentinel node). Successful sentinel node
localization was defined as finding either a blue node or a
radioactive node (greater than fourfold drop in axillary background
counts after removal of the hot node).
Among the patients who received both dye and radiocolloid by
intraparenchymal injection, 14% of sentinel nodes were found by blue
dye only, 11% by isotope only, and 67% by both blue dye and isotope,
for a total success rate of 92%.
Among those who received dye by intraparenchymal injection and
radio-colloid by intradermal injection, 3% of sentinel nodes were
found by blue dye only, 9% by isotope only, and 88% by both dye and
isotope, for an overall success rate of 100%. This indicates that
when both dye and radiocolloid are used, the difference between
intraparenchymal and intradermal injection of the radiocolloid (92%
vs 100% sentinel node localization) is not statistically significant.
Dr. Linehan also reported that the site of radiocolloid injection did
not influence the results of lymphoscintigraphy and that no patient
in either group had internal mammary node drainage.
Definitive validation would have
required back-up axillary lymph node dissection in all 200 patients.
As an alternative, the researchers measured concordance. A
concordant case was one in which the radioisotope and the blue dye
drained to the same sentinel node, producing a single node that was
both blue and hot, Dr. Linehan said.
Regardless of whether intraparenchy-mal or intradermal injection was
used, he said, the concordance was high, with no significant
difference between the two groups. The concordance data suggest
that the dermal and parenchymal lymphatics of the breast drain to the
same sentinel lymph node, he said. Since intradermal
injection is easier to perform and more effective, this technique may
simplify and optimize sentinel lymph node localization.