The US Food and Drug Administration last week approved Veridex’s GeneSearch breast lymph node assay, which the agency called the “first molecular-based laboratory test for detecting whether breast cancer has spread to nearby lymph nodes.”
According to Veridex, a Johnson & Johnson subsidiary, the test could potentially reduce the need for additional surgeries by detecting breast cancer in 0.2 mm of sentinel lymph node tissue.
The assay is an intra-operative test that analyzes tissue extracted from a sentinel lymph node using real-time reverse transcriptase PCR technology. The test operates on Cepheid’s SmartCycler platform and can generate results in 35 to 40 minutes, a marked improvement over the two to three days it takes to analyze tissue samples using standard pathology techniques.
According to Veridex, GeneSearch enables surgeons to test up to 50 percent of a sentinel node, as opposed to 5 percent typically examined under a microscope, which allows for the test to deliver more complete information to the oncologist regarding the stage of cancer that has metastasized to the lymph nodes.
However, despite these advantages, the test yielded “slightly more false positive results” than immediate microscopic examination, according to the FDA.
Veridex launched GeneSearch in the US July 16 and will begin shipping it immediately. The test was approved in the EU in November and is being used and tested in several other countries, a Veridex spokesperson said.
In a clinical trial of more than 300 patients, GeneSearch correctly identified 95.6 percent of subjects with lymph node metastases. In another study noted by the FDA, the test also showed a strong correlation to results from microscopic examinations of lymph nodes from 416 patients, and accurately predicted whether the cancer had spread to the lymph nodes in 88 percent of the women. In this study, patients without metastases were identified correctly 94 percent of the time.
Given these results, Veridex is touting the assay as a real-time tool that can help surgeons make decisions about whether to perform axillary lymph nodectomies while the patient is still on the operating table. This could prevent the need for a second operation in as many as 5,200 breast cancer patients in the US per year, Veridex said.
During a meeting of the FDA’s Immunology Devices advisory committee in November, Veridex officials described exactly how GeneSearch might aid surgeons make intraoperative decisions for their breast cancer patients.
Prior to removing a primary tumor from a patient, the surgeon would excise a sentinel lymph node and send the sample to the pathology laboratory for analyses. While the surgeon removes the primary tumor, the sample would be dissected in the laboratory, using the sample-preparation kit to extract the RNA.
After the assay reverse-transcribes and amplifies the RNA, the sample is loaded on to the Cepheid Smart Cycler II instrument. The SmartCycler generates a qualitative result, in the form of a positive or a negative, which is communicated to the surgeon.
With this information “the surgeon could then proceed to remove the axillary lymph nodes within the same surgery, if the result is positive, or if the result is negative, they could proceed to closing up the patient,” Lubna Syed, Veridex’s manager of regulatory affairs, told the advisory committee.
Although GeneSearch gave fewer false negative results than immediate microscopic examination, Veridex’s product gave “slightly more false positive results,” the FDA said.
According to the FDA, GeneSearch is able to detect molecules that are plentiful in breast tissue but scarce in normal lymph nodes. Since sentinel nodes are the first lymph nodes that filter fluid from the breast, metastatic clues will be found there first.
“The GeneSearch BLN Assay offers a new approach to sentinel node testing,” said Daniel Schultz, director of the FDA’s Center for Devices and Radiological Health, in a statement announcing the test’s approval. “Results of this rapid test are available while patients are on the operating table, providing a way for some women to avoid a second operation.”
Despite the test’s advantages over current options, comparisons of GeneSearch to intraoperative microscopic examination showed that although GeneSearch gave fewer false negative results than immediate microscopic examination, it gave “slightly more false positive results,” the FDA said.
“A false negative test result, when the cancer has actually spread, may delay the needed removal of additional lymph nodes,” the FDA said. “A false positive test, indicating metastasis when there is none, may result in a more extensive surgery and puts the woman at risk of unnecessary lymphedema (swelling due to fluid build-up following lymph node removal) and other side effects.”
Veridex said it plans to initiate two post-approval studies on the GeneSearch BLN Assay. The first study will further substantiate the turnaround time of the test when used intra-operatively, and a second study of more than 1,000 patients will validate the accuracy of the assay.