ARTICLES IN THIS WEB SITE IS FOR YOUR REFERENCE ONLY. IF YOU HAVE ANY QUESTION, YOU SHOULD CONSULT WITH YOUR
DOCTOR IMMEDIATELY. ALL RIGHT RESERVED 2008. DO NOT COPY NOR TRANSFER ARTICLES TO OTHER WEBSITES NOR OTHER
FORMS OF PUBLICATIONS.
|FDA Clears Test that Helps Identify Type of
Cancer in Tumor Sample
The U.S. Food and Drug Administration has cleared for
marketing a test that can help health care professionals
determine what type of cancer cells are present in a
The Pathwork Tissue of Origin test compares the genetic
material of a patient’s tumor with genetic information on
malignant tumor types stored in a database.
It uses a microarray technology to analyze thousands of
pieces of genetic material at one time. The test considers
15 common malignant tumor types, including bladder,
breast, and colorectal tumors.
"The clearance of the Pathwork test is another step in the
continued integration of molecular-based medicine into
standard practice," said Daniel Schultz, M.D., director of
the FDA's Center for Devices and Radiological Health,
which oversees medical diagnostics. "In the past,
scientists have classified different types of cancers based
on the organs in which the tumors develop. With the help
of microarray technology, they will be able to classify
these types of cancers in a standardized non-reader
dependent manner based on the patterns of gene activity
in the tumor cells."
The Pathwork Tissue of Origin test is the second in vitro
diagnostic multivariate index assay (IVDMIA) device to be
cleared by the FDA. In July 2007, the FDA issued a draft
guidance document to address premarket pathways and
postmarket requirements for IVDMIAs. IVDMIA tests
combine the values of multiple variables to yield a single,
Nearly every cell of the body contains a full set of
chromosomes and identical genes but only a fraction of
these genes are turned on or expressed in any given cell.
Gene expression occurs when certain molecular
information contained within DNA is transcribed to create
molecules known as RNA. These molecules in turn make
the proteins that perform most of the critical functions of
Microarray technology 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
Since RNA binds to its complementary DNA strand, how
much binding 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.
Pathwork’s proprietary software converts the scanned
image data to gene expression measurements. The gene
expression patterns are compared with known gene
expression patterns in the database that correspond to
different tumor types.
The Pathwork Tissue of Origin test has been found to
provide patterns that confirm existing tissue of origin of the
15 common tumor types using standard clinical and
pathological information. This accuracy of this test is
similar to that achieved by expert pathologists using
current standards of practice.
PathChip, the gene expression array used in the Pathwork
Tissue of Origin test, is custom-designed for Pathwork
Diagnostics of Sunnyvale, Calif., by Affymetrix Inc., of
Santa Clara, Calif. PathChip is the first custom Affymetrix
gene expression array to be cleared for diagnostic use.