Dye, Intradermal Radiocolloid Find the Sentinel Node

ORLANDO—Both 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 Oncology’s 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 meeting.

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 radiocolloid injection.

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 following questions:

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.”