Updated with stock information.

TUSTIN, Calif. (

TheStreet

) --The Mayo Clinic is denying statements made by

Radient Pharmaceuticals

( RPC) about the prestigious research hospital's involvement in a clinical study of Radient's cancer-screening test Onko-Sure.

"Mayo is not engaged in clinical studies with Radient and does not have a partnership agreement with Radient," Mayo Clinic spokesperson Kathy Anderson said in a statement emailed to

TheStreet

Friday.

Mayo Clinic's statement contradicts Radient's recent pronouncements regarding the pending release of results from a new clinical validation study of Onko-Sure, a blood-based cancer screening test. Questions about the exact nature of the relationship between Radient and Mayo come a week after similar doubts were raised about an

Onko-Sure venture in India touted by Radient

.

Radient shares fell 26% to 41 cents in Monday morning trading before the stock was halted around midday. The stock remains halted with no indication yet for when trading will resume.

In a press release issued Jan. 18, Radient said it was making "progress on its clinical study with Mayo Clinic for the validation of the company's US FDA-cleared Onko-Sure" test. Results from this study are expected before the end of the first quarter.

The same Radient press release described the Onko-Sure clinical study as one in which "1,000 colorectal patient samples with various disease stages are being tested in parallel by RPC

Radient and Mayo..."

Onko-Sure is a blood-based test cleared for use in the U.S. to measure the progression of colon cancer in patients already diagnosed with the disease. Despite FDA approval,

Radient has failed to generate significant revenue from Onko-Sure

, placing the company's financial health in severe jeopardy.

Radient is hoping that results from this new study will generate interest and sales of Onko-Sure to oncologists. Radient's moribund stock price is in desperate need of a revamp too, so invoking the imprimatur of Mayo Clinic has been a prominent part of the company's public relations strategy. But in linking Mayo Clinic to Onko-Sure, Radient appears to be exaggerating the research hospital's involvement and interest.

In order to conduct the Onko-Sure study, Radient needed blood samples taken from patients with colon cancer, so the company turned to a subsidiary of Mayo that collects and stores tissue and blood samples for use in scientific research. The Mayo Clinic subsidiary sold the blood samples to Radient.

"Mayo Clinic does have a collaboration agreement with Radient whereby Mayo Validation Support Services provided bio specimens from our Bio Specimen Bank to Radient for clinical studies," said Mayo spokesperson Anderson.

"The services Mayo was required to provide to Radient have been fulfilled. Any clinical study results about Onko-Sure would be provided by Radient, not Mayo Clinic," she added.

Radient was informed of Mayo's statement regarding the Onko-Sure clinical study but a spokesperson for the company declined to answer questions or comment.

In the area of new colon cancer-screening tests, Mayo Clinic is much more directly involved with work being conducted by

Exact Sciences

(EXAS) - Get Report

.

Last year,

Exact Sciences and researchers at Mayo conducted a clinical validation study

of a new gene-based screening test for early-stage colon cancer. The Mayo Clinic's Dr. David Alquist presented results from that study at a medical meeting last fall. Exact Sciences and Mayo Clinic have an ongoing collaboration to develop this new colon-cancer screening test, which has showed potential to be one of the first non-invasive cancer diagnostics to detect accurately colon cancer at its earliest and most treatable stages.

Radient's Onko-Sure is cleared for sale in the U.S. as an "an aid in monitoring the disease progression of patients who have been diagnosed previously with colorectal cancer. Results of DR-70 (FDP) testing should be used in conjunction with other clinical modalities that are standard of care for monitoring disease progression in these patients," according to the FDA's approval letter.

DR-70 is an older brand name for Onko-Sure and the test has not been proven to detect colon cancer, according to FDA. What Onko-Sure does is pick up an increase in blood levels of a biomarker known as fibrinogen degradation products (FDP) that can, but doesn't always, signal disease progression, aka tumor growth. Even if Onko-Sure is correct in signaling cancer progression (or even the first instance of cancer) the test cannot tell a doctor where the cancer is located.

Radient says the new clinical validation study is designed to prove the superiority of Onko-Sure over an older colon cancer screen known as the carcinoembryonic antigen (CEA) test, particularly in patients with earlier stage disease. Radient, however, has not explained how this new validation study will be used to market Onko-Sure as a test to detect or diagnose early-stage colon cancer. Any claim that Onko-Sure detects colon cancer would have to be submitted to the FDA for review and approval.

Onko-Sure sales for the first nine months of 2010 totaled $116,000, a 15% decrease from sales in the first nine months of 2009. That puts Radient well off its stated guidance calling for $7.6 million in Onko-Sure sales for all of 2010. Radient has yet to announce fourth-quarter and year-end 2010 results.

Radient shares closed Monday at 57 cents.

--Written by Adam Feuerstein in Boston.

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