Quanterix, a diagnostics startup in Cambridge, MA, has developed a highly sensitive new technology capable of detecting a single, cancer-linked molecule in blood, to predict the recurrence of prostate cancer. In a new study of 30 men who had their prostates removed, the test could detect low levels of the molecule that commercial assays missed.
Single occupancy: Reaction wells 4.5 microns in diameter cradle single immunoassay beads. A single protein clings to a bead and traps a fluorescent enzyme, lighting up the well when it is placed in a detector.
Quanterix’s new detection technology counts the number of prostate specific antigen (PSA) molecules released by the cells of the prostate gland into the blood. In cancer patients who have had their prostates removed, PSA levels drop to below commercially detectable levels six weeks after surgery. An increase in PSA concentration over time is one indication that the prostate cancer has returned.
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In this new method, PSA molecules are trapped on beads and isolated individually on arrays of tiny wells. A fluorescent enzyme added to the array lights up when it binds to PSA, revealing the number of PSA molecules in the sample.
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According to the new study published in Nature Biotechnology, the test is 1,700 times more sensitive than other PSA detection methods used in clinical laboratories. Researchers found that while commercial assays detected no PSA in any of the blood samples, the Quanterix assay found PSA present in very tiny levels in all samples. Quanterix has yet to establish a cost for the test.
“I think we’ve made strides being able to decrease the threshold of detection, and I hope that we’ll be able to extend this,” says Herbert Lepor, chairman of the department of urology at New York University Langone Medical Center. Though unconnected with the development of Quanterix’s PSA test, Lepor says he plans to share his bank of blood samples with Quanterix to help standardize the assay. “I’m excited enough to commit our valuable resource of serum samples to give us a barometer of how this test will perform,” he says.
Urologists typically screen their patients for cancer recurrence for several years following prostatectomy surgery, but the sensitive new test could pinpoint which patients are at higher risk of cancer recurrence and should therefore be monitored more frequently. With available PSA tests, Lepor waits three years following surgery before making predictions about which patients are at a higher risk of cancer recurrence. With a more sensitive assay, he hopes to make this call sooner.
There is a possibility that the test will be too sensitive, detecting PSA even in the absence of prostate cells. Lepor says that if this is the case, it may not be the absolute nadir that determines the probability of recurrence, but the rate of change of PSA levels over several weeks.
Researchers at Quanterix are working on applying their hypersensitive detection technology to Alzheimer’s and Parkinson’s disease. They hope to identify biomarkers linked to these diseases that are detectable at very low levels in blood. “It’s just the tip of the iceberg for us,” says David Duffy, senior director at Quanterix. “The ability to measure single molecules in blood is going to be applicable across a whole lot of other areas.”
