Test Determines Origin of Hard-to-Identify Tumors

A gene expression test helps diagnose hard-to-identify tumors, which could benefit more than 200,000 cancer patients every year in the United States.

The proper identification of a tumor's origin should allow the patient to receive a diagnosis sooner; enable effective cancer-specific treatment to begin more quickly; avoid the toxicity of broader, and in some cases, ineffective chemotherapy; and perhaps even to survive longer. Currently technologies available for hard-to-identify tumors are time-consuming, frustrating for both physicians and patients, expensive to the healthcare system and often do not provide clear answers. Knowing the primary tumor site is particularly important with the increased availability of new, targeted cancer therapies.

The new test uses microarray technology, which can simultaneously measure gene expression levels of large numbers of genes. Small DNA fragments are placed or arrayed on a slide and then RNA, which has been extracted from the tumor tissue and labeled with a fluorescent marker, is spread over this microarray. Because RNA binds to its complementary DNA strand, the amount of binding that occurs indicates how active the gene being evaluated is. This can be determined by putting the array under a scanning microscope and measuring the intensity of the fluorescent light at each point on the array.
Software converts the scanned image data to gene expression measurements. The gene expression patterns are compared with known gene expression patterns that correspond to different tumor types in the database

An in vitro diagnostics clinical validation study of the new test was performed. The test demonstrated an average 94 % overall concordance across four laboratories in a cross-laboratory comparison study of 60 metastatic, poorly differentiated, and undifferentiated tissue specimens.

The new test is called the Pathway Tissue of Origin test and is a product of Pathway Diagnostics (Sunnyvale, CA, USA). The test was cleared by The U.S. Food and Drug Administration (FDA; Rockville, MD, USA). Deborah J. Neff, president and CEO of Pathwork Diagnostics said, "We believe the Pathwork Tissue of Origin Test will help provide more certainty in tumor diagnosis, which will enable more patients to realize the benefits of this new era in genomics-based diagnostics.”

PathChip, the gene expression array used in the Pathwork Tissue of Origin test was custom-designed for Pathwork Diagnostics by Affymetrix, Inc. (Santa Clara, CA, USA). PathChip is the first custom Affymetrix gene expression array to be cleared for diagnostic use.

The Pathwork Tissue of Origin test will be available as an in vitro diagnostic (IVD) kit, meaning that clinical laboratories will be able to run the test themselves. A functionally equivalent version of the test is also available through Pathwork Diagnostics Laboratory.


Related Links:
Pathway Diagnostics
Affymetrix
Food and Drug Administration