The Pathwork® Tissue of Origin Test is the first gene expression test cleared by the FDA for use in determining the origin of uncertain tumors. A tumor's gene expression pattern is a new type of molecular diagnostic test that clinicians can use, in addition to existing immunohistochemistry (IHC) and imaging tools, to make a definitive diagnosis. The Pathwork Tissue of Origin Test measures the expression pattern, comprising more than 1,500 genes, in an uncertain tumor to compare it to expression patterns of a panel of 15 known tumor types, representing 60 morphologies overall. It produces a report with an objective, probability-based score for each potential tissue. The test uses a proprietary Pathchip® microarray and runs on the proven Affymetrix GeneChip® System.

Pathwork Diagnostics Laboratory (PWDL) is a CLIA-certified laboratory, located in Sunnyvale, California. For the Pathwork Tissue of Origin Test, oncologists and pathologists can provide qualified frozen tissue specimens to the laboratory for processing and analysis. A Pathwork staff pathologist interprets the results and provides a comprehensive report to the physician. Pathwork Diagnostics Laboratory also provides an extensive reimbursement program to support patients with financial hardship and those patients who are uninsured and underinsured and to assist physicians in ordering the Pathwork Tissue of Origin Test.

In the United States, an estimated 200,000 newly diagnosed cancer patients each year may have a tumor for which the site of origin is unknown after the initial diagnostic workup.^1-4 Such hard-to-identify tumors are time-consuming to work up, frustrating for physicians and patients, and expensive for the healthcare system. Existing diagnostic technologies often do not provide clear answers.

Cancers are classified and treated according to where they began (i.e., their primary site), regardless of where in the body they are found. Accurately identifying a tumor's origin is necessary for beginning standard-of-care, cancer-specific treatment per National Comprehensive Cancer Network (NCCN) Clinical Practice Guidelines. This is particularly important given the increasing availability of new cancer therapies that target specific tissues and their genomic components, rather than using a "one-size-fits-all" approach.

Targeted therapies can be effective even with metastatic tumors and are generally tumor-specific (e.g., Herceptin for breast cancer), requiring identification of the primary tumor site/tissue of origin. Targeting therapy to specific tumor types can allow patients to avoid the toxicity of broader, and in some cases, useless chemotherapy.

Diagnostic workups for hard-to-identify tumors typically include extensive immunohistochemistry (IHC) and various imaging studies, such as x-rays and computed tomography. Obtaining results for these can often take weeks as clinicians rely on a trial-and-error and necessarily iterative approach. IHC does not cover all tumor types and requires human review that can be subject to errors. One study showed that IHC was only 67 percent accurate at identifying the primary site of metastatic tumors.⁵

A tumor's site of origin may be elusive because the original tumor may be small, avoiding detection by imaging and other techniques. Additionally, cells of the tumor in question may have changed appearance and thus may no longer resemble tumors from the originating site (i.e., they have become poorly differentiated or undifferentiated).

The test demonstrated 89 percent positive agreement (akin to sensitivity) and 99 percent negative agreement (akin to specificity) with available diagnoses in the in vitro diagnostic (IVD) clinical validation study submitted to the FDA, which consisted of 545 metastatic, poorly differentiated and undifferentiated tumors that had been diagnosed as one of the 15 tumor types on the panel using existing methods.⁶ The Pathwork Diagnostics Laboratory version of the test is functionally equivalent.

Additionally, the test demonstrated an average 94 percent overall concordance across four laboratories in a cross-laboratory comparison study of 60 metastatic, poorly differentiated and undifferentiated tissue specimens.⁷

Yes. Physicians may order the Pathwork Tissue of Origin Test as a service through the CLIA-certified Pathwork Diagnostics Laboratory. Additionally, the company plans to make the FDA-cleared test available later this year to clinical laboratories in a kit format so that they can run the test themselves. Qualified frozen tissue specimens may be provided to the Pathwork Diagnostics Laboratory for processing and analysis. A Pathwork staff pathologist interprets the results and provides a comprehensive report to the physician.

For each tumor specimen, the Pathwork Tissue of Origin Test Report provides an objective probability-based score for each of the following tumor types: bladder, breast, colorectal, gastric, hepatocellular, kidney, non-small cell lung, non-Hodgkin’s lymphoma, melanoma, ovarian, pancreatic, prostate, soft tissue sarcoma, testicular germ cell and thyroid. The test provides an objective result with the ability to rule in or rule out tissues to increase the certainty of the diagnosis. When ordered through Pathwork Diagnostics Laboratory, the Pathwork Tissue of Origin Test Clinical Report is interpreted and signed by a Pathwork staff pathologist. For the FDA-cleared IVD kit version of the test, clinical laboratories will run the test themselves and provide results directly to the physician.

These 15 tumor types represent 60 morphologies overall and cover approximately 90 percent of solid tumors, including those most likely to metastasize. In addition, based on input from oncologists, these 15 types of cancer were considered most likely to present as uncertain and, once identified, would have the most clinical value in terms of treatment decisions.

The test must be ordered by a physician. Typically, after a biopsy of a metastatic lesion is taken, the primary tumor site is identified through patient history, imaging procedures, morphology and a panel of IHC markers. If tumor origin is still uncertain after these steps, the Pathwork Tissue of Origin Test can be used to identify the primary tumor site. Following are specific examples of situations in which the test might be beneficial:

• The cancer is found in an unexpected location.
• The tumor's cells are poorly differentiated or undifferentiated, making them difficult to interpret
• The cancer is found in multiple locations, demonstrating metastatic disease without a clear primary site.

Pathwork is working with insurance companies to secure coverage of the test and anticipates that reimbursement for the test will be on par with other high-value genomics-based tests. In the case of tests ordered through Pathwork Diagnostics Laboratory, Pathwork is prepared to take formal assignment of benefits whenever possible and submit insurance claims on behalf of insured patients in the U.S. for the Pathwork Tissue of Origin Test. We do not expect institutions or healthcare providers to order this test from Pathwork Diagnostics Laboratory and then bill third-party payers on their own, except where required to comply with billing regulations or policies, or pre-existing contractual arrangements. The Pathwork Reimbursement Assistance Program (RAP) provides billing and reimbursement support to patients, including a financial assistance program when payers decline payment. For more information, contact Pathwork Diagnostics Laboratory Customer Support by calling toll-free 1.877.808.0006 and selecting the option to speak with a RAP counselor, or e-mail . You can also visit www.pathworkdx.com.

Tissue specimens should be obtained by routine procedures and snap frozen within 60 minutes of biopsy or excision. As determined by hematoxylin and eosin (H&E) staining of an adjacent frozen section, the specimen must contain at least 60 percent viable tumor and no more than 20 percent necrotic tissue. Specimen size received must be a minimum of 100 mg of tissue. A version for formalin-fixed, paraffin-embedded (FFPE) tumor specimens and needle biopsy specimens, including core and fine needle aspiration (FNA), will be available through Pathwork's CLIA laboratory later this year.

In comparison to other technologies, microarrays enable thousands of genes to be evaluated simultaneously. Using more genes provides better results when analyzing complex diseases such as cancer and enables better standardization, which yields a more robust test with better reproducibility.

Call Pathwork Diagnostics toll-free at 1.877.808.0006.

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2. Tong KB, Murtagh KN, Hubert HB, et al. Incidence, costs of care and mortality of Medicare beneficiaries diagnosed with cancer of unknown primary origin. Poster presented at the annual meeting of the American Society of Clinical Oncology; June 2-6, 2006; Atlanta, GA.
3. Pathwork Diagnostics analysis.
4. American Cancer Society, Cancer Facts & Figures 2008. Atlanta: American Cancer Society; 2008.
5. Dennis JL, Hvidsten TR, Wit EC, et al. Markers of adenocarcinoma characteristic of the site of origin: development of a diagnostic algorithm. Clin Cancer Res. 2005;11(10):3766-3772.
6. Pathwork Tissue of Origin Test User Guide (P/N 72912).
7. Dumur CI, Lyons-Weiler M, Sciulli C, et al. J Mol Diagn. 2008;10:67-77.