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Melanoma may metastasize in less radioactive sentinel lymph nodes
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Microscopic melanoma metastases may occur in lymph nodes other than the hottest node, thus warranting their removal, according to results of a single-institution study.
Standard of practice ranges in the surgical removal of sentinel lymph nodes, from removal of only the hottest — or most radioactive — lymph node, to removal of all lymph nodes with radioactivity greater than 10% of the hottest lymph node.
Lyn M. Duncan, MD, associate pathologist and director of dermatopathology at Massachusetts General Hospital, and colleagues sought to determine the clinical significance of melanoma in less radioactive lymph nodes and to determine the risk of disease progression associated with sentinel lymph node status and tumor characteristics.
The researchers retrospectively analyzed 1,575 sentinel lymph nodes from 475 patients with cutaneous melanoma who had lymph nodes resected at Massachusetts General Hospital between 2004 and 2008. The mean follow-up was 4.9 years, and the last year of follow-up was 2012.
All lymph nodes with radioactivity greater than 10% of the hottest lymph node were resected.
Overall, 91 patients (19%) had positive sentinel lymph nodes, 79% of whom had metastases in the hottest sentinel lymph node. The other 19 cases (21%) had a tumor that was not in the hottest node. In those cases, radioactivity ranged from 26% to 97% of the hottest node.
Among patients with sentinel node metastases, 43% had disease progression, regardless of whether the hottest node was positive or negative. In patients with negative lymph nodes, 11% still developed metastases beyond the sentinel node basin and an additional 3.4% recurred within the basin.
There was an association between mortality and the mitogenicity of the primary tumor (OR = 2.43; 95% CI, 1.35-4.39).
Researchers noted that if the surgeons had only removed the hottest node, there would have been 19 false-negative results. These data would represent 4% of all patients and 21% of patients with positive nodes.
For patients with at least one positive sentinel node, 8-year survival was less than 55% and the presence of more than one mitosis per square millimeter in the primary tumor was associated with decreased survival rates.
The presence of sentinel lymph node metastasis was associated with reduced RFS and melanoma-specific survival (P ˂ .001); however, prognosis did not differ if the metastasis was present in the hottest node or not.
“We demonstrate that the current practice of removing nodes with more than 10% radioactivity of the hottest sentinel lymph node is not too exhaustive,” the researchers wrote. “Our study demonstrates that, at times, it is not even the second or third, but sometimes it is the fourth hottest node that contains metastasis. Furthermore, the distribution of tumor size in these non-hottest nodes was comparable with the distribution in the hottest, demonstrating that these nodes were equally significant in tumor burden.” – by Anthony SanFilippo
Disclosure: The researchers report no relevant financial disclosures.
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