A new molecular assay test improves the accuracy of finding cancer in the lymph nodes during a sentinel lymph node biopsy, according to results presented by researchers Saturday at the San Antonio Breast Cancer Symposium.
Results of the study showed that the GeneSearch BLN Assay test, developed by Veridex LLC and approved by the FDA in mid-July, is about 10 percent more sensitive than traditional histology and microscopic exams in finding evidence of tumor cells during a sentinel lymph node biopsy.
One of the challenges of the sentinel lymph node biopsy is that a pathologic examination of the lymph nodes must be done during a halt in the surgery to assess whether there is a tumor in the sentinel nodes. Traditionally, surgeons conduct a sentinel lymph node biopsy by removing less than 5 percent of the lymph node during an intra-operative halt in the surgery. The small node section is then frozen and examined under a microscope for the presence of cancer cells. If cancer cells are found in the nodes, the surgeon will typically remove these lymph nodes during the biopsy procedure.
However, all too often the results of this assessment are inaccurate, requiring the patient to undergo the physical and emotional stress of returning to the operating room for yet another surgical procedure to remove the cancerous lymph nodes.
The GeneSearch molecular assay test, which the FDA approved as a replacement for the standard frozen section method of examining the sentinel lymph nodes during a biopsy, is an ultra-rapid method of doing a genetic screening test to look for evidence of tumor cells in the lymph nodes during the intra-operative halt in the surgery. Researchers reported that this new technique is more sensitive than frozen section, without sacrificing specificity.
Researchers did both standard frozen section and molecular assay tests on 319 breast cancer patients. The pathologists who did the frozen section did not know the results of molecular assay test, and vice versa. After both diagnostic tests were completed, researchers compared the results from each test to the final pathologic report on each patient.
According to Dr. Peter Blumencranz, lead investigator of the study, surgical oncologist and medical director of Moffitt Morton Plant Cancer Care at Morton Plant Hospital in Clearwater, Fla., the GeneSearch assay test correctly diagnosed patients for cancer 91 percent of the time.
Compared with the 65 percent accuracy of the frozen section in detecting tiny breast cancers, the GeneSearch test displayed a remarkable improvement from the traditional pathologic examinations currently in use for sentinel lymph node biopsies.
"Since we began using this test at our [medical] center on Aug. 1, we have tested 85 patients with the molecular assay and only one of them [received a false negative] and had to come back for a second surgery," Blumencranz said. "But in fact, more than that percent is missed in standard histology. So what is the greater truth? Looking at 50 percent of the node with the assay or what amounts to only about 5 percent of the node by microscopic exam."
But despite the proven increased sensitivity of the GeneSearch test in finding small and hard-to-diagnose cancers, some doctors remain more concerned about the risk of false positives from the molecular test than the risk of false negatives.