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Assay has high sensitivity for hard-to-detect SLN mets

Assay has high sensitivity for hard-to-detect SLN mets

SAN ANTONIO—A rapid molecular assay outperforms frozen sections when it comes to detecting breast cancer metastases in sentinel lymph nodes (SLNs), new data show. Moreover, the assay tends to perform better in cases where detection of metastases by frozen section is known to be difficult, such as cases of lobular carcinoma.

"In this era of sentinel node biopsy, we are not removing all of the axillary nodes, and histology varies all over the country, if not all over the world, in terms of its sensitivity and ability to pick up disease," Peter W. Blumencranz, MD, said at the 2007 San Antonio Breast Cancer Symposium (abstract 53). "So if we can come up with a more reproducible, standardized program to assess nodal involvement, I think it will behoove us—surgeons and pathologists—as the patients' advocates, to be able to tell them if there is disease in those nodes."

The molecular assay studied, the GeneSearch Breast Lymph Node (BLN) Assay, which was FDA approved in July 2007, is based on detection of two markers—cytokeratin 19 and mammaglobin—in sentinel nodes by reverse transcription-polymerase chain reaction (RT-PCR), said Dr. Blumencranz, a breast surgeon at Morton Plant Mease Health Care, Clearwater, Florida, and medical director of Comprehensive Breast Health Services.

The assay can evaluate up to half of the node, and the result is reported as positive if either or both markers are detected, Dr. Blumencranz said. "This is a rapid test. It can be done in less than 40 minutes, so the surgeon can get this information in the operating room if he wishes to make a decision to proceed with an axillary node dissection," he noted.

Multicenter study

In the prospective, multicenter trial, 490 women with invasive breast cancer underwent axillary lymph node dissection with sentinel lymph node sectioning and evaluation of adjacent sections for metastases by the molecular assay, by frozen section, and by permanent paraffin section (the comparator).

Many of the women had features known to make it difficult to assess for metastases by frozen section: 11% had lobular carcinoma, 45% had T1 tumors, 42% had grade 1 tumors, and 2% had received neoadjuvant therapy.

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