Test Detects Prostate Cancer 'Smell' Just Like Trained Dog

Kristin Jenkins

April 11, 2017

The latest chapter in research efforts to find a noninvasive diagnostic test for prostate cancer reveals that much of the progress is continuing to go to the dogs...

Researchers at Indiana University–Purdue University Indianapolis (IUPUI) have identified the molecular signature for the "smell" of prostate cancer that floats in the headspace above a urine sample. This appears to be the "smell" that trained dogs home in on. A few years ago, Italian researchers found that dogs could be trained to sniff hundreds of urine samples and detect prostate cancer with an accuracy of almost 100%, as reported at the time by Medscape Medical News.

Now the IUPUI researchers say that by artificially recreating the same smell, they can do what dogs do – but maybe not quite as accurately, as their test has 89% sensitivity and 92% specificity.

"If dogs can smell prostate cancer, we should be able to, too," said Amanda Siegel, PhD, a postdoctoral research associate for the Integrated Nanosystems Development Institute at IUPUI. She presented the new results at the National Meeting and Exposition of the American Chemical Society (ACS) in San Francisco, California.

The team also hopes to develop a noninvasive urine stick or strip that can be used in a physician's office to noninvasively screen for prostate cancer and reduce the number of unnecessary prostate biopsies by about half, said principal investigator Mangilal Agarwal, PhD, director of the Integrated Nanosystems Development Institute and associate professor of mechanical engineering at IUPUI.

About two thirds of men who are recommended for biopsy because of elevated levels of prostate specific antigen (PSA) are found to have either no sign of prostate cancer or an indolent form for which no treatment is required, Dr Agarwal pointed out. Morbidity associated with the procedure can be significant and includes increased risk for infection and up to 10 days of pain post biopsy.

 
This is not a test yet. It's just the beginning of creating a test. Dr Mangilal Agarwal
 

"We hope our test will identify people who actually require biopsy and not just those with high PSA test results," Dr Agarwal said, adding, "This is not a test yet. It's just the beginning of creating a test."

The team also wants to "better understand the metabolic pathways that will help doctors better treat patients," Dr Agarwal told Medscape Medical News. The molecular signature can also be used to distinguish between indolent and aggressive prostate cancer.

Detecting the "Smell"

For the study, the researchers collected urine samples from 85 men before they underwent annual prostate biopsy at the Richard L. Roudebush VA Medical Center in Indianapolis. All patients had been referred for prostate cancer screening because of high PSA levels, nodules discovered on digital-rectal examination, or a family history of prostate cancer.

The researchers used gas chromatography–mass spectrometry to identify the volatile organic compounds floating in the headspace above the urine samples. Results showed that a small set of molecules was present in 90% of samples from patients with prostate cancer but was absent in samples from patients without disease.

When these findings were combined with the pathology findings, "we had some pretty remarkable results," Dr Siegel said. The molecular signature correctly identified 29 of 33 patients with a Gleason score of 7+; 35 of 38 patients who did not have cancer; and 10 of 14 with indolent cancer and a Gleason score of 6.

The team is now planning a multicenter study in 250 to 300 patients to validate their findings. They would also like to confirm the molecular signature they have identified by comparing their results with those of a trained canine sniffer.

"Once we identify the biomarkers, we can artificially recreate the smell [of prostate cancer] and then validate the smell with trained canines so these biomarkers can be easily accessed by the medical community," Dr Agarwal said. "Our work could revolutionize the diagnosis of prostate cancer."

Dr Agarwal is no stranger to working with dogs. At the time the Italian study piqued his interest, the team had been working to identify the molecular signature of hypoglycemia in breath samples that dogs had been trained to detect.

The study received funding from the Richard L. Roudebush VA Medical Center. The researchers have disclosed no relevant financial relationships.

National Meeting and Exposition of the American Chemical Society (ACS). Presented April 3, 2017.

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