Just six months after receiving CLIA certification to launch its Previstage GCC Colorectal Cancer Staging Test, DiagnoCure Oncology Laboratories (West Chester, Pennsylvania) has received powerful confirmation that the biomarker it uses in its cancer staging test is right on the money.

Parent company DiagnoCure (Quebec City) owns the exclusive worldwide diagnostic rights to the Guanylyl cyclase C (GCC) biomarker, and since last September has marketed the Previstage GCC test to physicians for patients who seem to be at low risk of colorectal cancer recurrence.

"We know that, presently, histopathology methods which determine a patient to be cancer-free in reality produces a result where up to 30% do in fact recur," John Schafer, president/CEO of DiagnoCure, told Diagnostics & Imaging Week. "So a lot of physicians make decisions differently on which patients are classified by histopathology that they should treat. This test and this JAMA article concludes that by using a molecular diagnostic method of amplifying GCC as a marker picks up those patients who have a higher risk of recurrence."

This week the Journal of the American Medical Association (JAMA) published the positive results from a prospective five-year multi-center study of more than 400 enrolled patients that demonstrated the value of the biomarker and the test. The study was conducted by investigators from Thomas Jefferson University (Philadelphia), with contributions from McGill University (Montreal) and the Fox Chase Cancer Center (Philadelphia), among others.

GCC is a gene coding for a protein that's expressed in colorectal cells, both normal and cancerous. But it's never found in normal tissue in other parts of the body. When GCC is detected in lymph nodes removed during colorectal cancer surgery, it is an indication of the presence of colorectal cancer metastases.

"There are 50 studies referenced with this test, but this is the first that is five-year prospective, double-blinded study that was sponsored by the National Institutes of Health," Schafer said. "A prospective study for a diagnostic test is unusual, so we're very happy."

He explained that if patients in the study were classified as cured or node-negative by a pathologist report and GCC was present, they were 4.7 times more likely to have cancer recur than those were negative for the biomarker.

"It's [GCC] a very big indicator of risk higher than any other risk factors that were evaluated in this patient population," Schafer said.

The test is marketed for doctors to use in patients who are classified as node-negative by histopathology. It helps physicians as they try to decide if a patient should or shouldn't be treated with adjuvant chemotherapy.

Schafer said the test is conducted with paraffin-embedded tissue that's stored from a patient's initial surgery, meaning no additional biopsies or tests are required.

"They just have to throw it in the envelope and mail it to our lab," he said. "No patient involvement is necessary."

Current treatment protocols indicate that patients who are considered to have a lower risk of recurrence by histopathology do not receive adjuvant treatment, such as chemotherapy, after their surgery. But most oncologists know that histopathology, which consists of microscopically examining thin slices of the lymph nodes, is imperfect and up to 30% of histopathology node-negative patients experience disease recurrence and face greater risk of death.

DiagnoCure's GCC biomarker and its technology is 100,000 times more sensitive than the current microscopic method. With GCC testing, patients can receive personalized treatment if necessary while those who are at lower risk of disease recurrence can avoid the negative side effects of treatment.

Next up for DiagnoCure is a GCC blood test that can be used to monitor for recurrence of colon cancer. Studies show that the presence of GCC in the blood may be an early indicator of micrometastases that would otherwise escape detection by the current standard methods of monitoring. Typically physicians have relied on a blood test, scheduled at regular intervals, to measure levels of a protein called carcinoembryonic antigen (CEA). But CEA is limited as a marker for colon cancer, detecting less than 60% of recurrent tumors and it has a high false positive rate.

"We also have another five-year study for GCC as a blood test," Schafer said. "That study will be opened up this year. It's to answer the question, Is my colon cancer coming back?' Today we can't answer that very well. We find out it has come back by X-ray or tumor development and then it's too late."

But, he added, "GCC cancer cells may lodge themselves somewhere in the body and then are not destroyed by chemotherapy. If they start to form a tumor, they slough off GCC cells. By measuring periodic GCC levels in the patient's blood, we'll be able to determine whether or not the cancer is growing somewhere else in the body very early and we think adjuvant chemotherapy at that early stage will be of benefit. So, that's coming down the pike."

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