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PCR-Based Lymph Node Assay Is More Sensitive Than Old Intraoperative Tests


 

SAN ANTONIO — A new PCR-based assay is substantially more sensitive than current methods of intraoperative detection of breast cancer nodal metastases—and that translates into less need for second lymph node procedures, Dr. Peter W. Blumencranz said at a breast cancer symposium sponsored by the Cancer Therapy and Research Center.

“Secondary surgery on the axilla increases costs, causes time and scheduling problems, and most importantly adds to the physical and emotional burden on the patient,” noted Dr. Blumencranz, medical director of comprehensive breast health services at Morton Plant Mease Health Care, Clearwater, Fla.

The GeneSearch Breast Lymph Node (BLN) assay measures expression levels of two markers of nodal metastases: mammaglobin and cytokeratin 19. The thresholds employed in the assay reliably permit identification of metastases larger than 0.2 mm (those deemed clinically significant in guidelines) while disregarding smaller ones.

Dr. Blumencranz presented data from a multicenter prospective study comparing the BLN assay's performance with the standard intraoperative tests: frozen section and touch preparation cytology.

The yardstick for comparison was permanent section hematoxylin and eosin histology, which is considered the preferred method in terms of accuracy, although results take several days. The study population consisted of breast cancer patients without clinically evident metastases who underwent sentinel lymph node biopsy—the standard of care in staging the axilla.

The BLN assay outperformed frozen section in terms of sensitivity by an absolute 10% and touch prep by an even wider margin while maintaining high specificity. (See graph, right.)

Noting other advantages of the assay, Dr. Blumencranz said that it can be performed by a technician with minimal training, and that it samples 50% of the node, compared with the 2%–5% sampled with permanent section histology. Six nodes can be sampled in a single run.

It takes 35–40 minutes from the time a surgeon removes the sentinel node for the BLN assay to yield a yes/no answer. A pathologist in the audience at the symposium argued this is an inefficient use of time, since the BLN test takes three times as long as a frozen section.

Dr. Blumencranz replied that a frozen section requires 20–25 minutes at most centers. He added that the cost of the extra 10–15 minutes in the operating room is more than offset by the savings accrued from reducing the number of reoperations needed when a sentinel node biopsy comes up positive by permanent section histology several days after a negative intraoperative frozen section or touch prep.

The comparative study was sponsored by Veridex LLC, a Johnson & Johnson company.

The BLN assay became commercially available in the European Union in November 2006, and a Food and Drug Administration advisory panel recommended its approval at that time.

Dr. Blumencranz has received research support from Veridex.

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