Low-radioactivity sentinel lymph nodes should be removed

NEW YORK (Reuters Health) - In women with breast cancer, sentinel lymph nodes with low radioactivity should be removed to ensure that all positive nodes have been resected, according to a report in the December Journal of the American College of Surgeons.

"In order to reduce the false-negative rate, the surgeon needs to take out not only the hottest lymph node but also additional ones, as low as to, at least, 10% of the hottest lymph node," Dr. Stanley P. Leong from University of California, San Francisco, told Reuters Health.

Dr. Leong and colleagues sought to validate the hypothesis that while the hottest sentinel lymph node (SLN) has the highest likelihood of harboring tumor cells, the "10% rule" - all nodes with more than 10% of the ex vivo radioactive count of the hottest SLN should be removed - may be applied without sacrificing the sensitivity of the procedure.

Among 332 primary breast cancer patients who underwent sentinel lymphadenectomy, the radioactivity of the positive nodes apart from the hottest node ranged between 0.8% and 90% of the counts of the hottest lymph node, the authors report, but only 6.5% of radioactive nodes had less than 10% of the radioactivity of the hottest lymph node.

Only 9 lymph nodes (15%) with radioactive counts less than 10% of the hottest lymph node were found to harbor tumor cells, with the lowest radioactivity of a node positive for cancer reaching 4.2% of the hottest node.

If only the hottest node was removed, the false-negative rate was 14.1% and the accuracy 96.7%, the researchers note. If the 10% rule was applied, the false-negative rate dropped to 6.4% and accuracy increased to 98.5%.

"These findings indicate that there (is) more than one sentinel lymph (node), suggesting that more than one lymphatic channel can lead the cancer cells to one or more sentinel lymph nodes," Dr. Leong said.

"We have developed the hypothesis that multiple lymphatic channels may exist to drain into more than one sentinel lymph node," Dr. Leong added. "Based on this hypothesis and others, I have organized two international symposia on Cancer Metastasis and the Lymphovascular System: Basis for Rational Therapy. The upcoming 3rd International Symposium will be held in San Francisco from May 6-9, 2009."

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