New research from Finland suggests in the not-too-distant future we may be making rapid, early diagnoses of prostate cancer using a noninvasive electronic nose that sniffs a urine sample.
In a report of their proof of principle study in the Journal of Urology, researchers from the University of Tampere describe how the "eNose" successfully differentiated between prostate cancer and benign prostatic hyperplasia (BPH) by analyzing the "smell print" of the headspace of a urine sample (the air immediately above the urine).
The team says the results from the eNose are comparable to those obtained from prostate specific antigen (PSA) tests.
Prostate cancer is the second most common cancer in men and one of the leading causes of death from cancer. It is not easy to diagnose and make reliable prognoses about prostate cancer because it does not appear consistently in prostate tissue.
Currently, doctors rely on the digital rectal exam (DRE) and the PSA test to help decide if a biopsy is necessary. But these can be hit and miss, while biopsies are costly and uncomfortable, and carry the risk of infection. The other problem with current methods is that many diagnosed prostate cancers will not become life-threatening, and aggressive treatment risks reducing quality of life without extending it.
Odor sampling begins to show promise as a diagnostic for cancer
There have been experiments to test dogs' ability to sniff out cancer, but scientists have noticed a lot of variation in their performance between and during studies.
About 20 or so years ago, researchers became interested in reports that dogs were detecting cancer in their owners, and since then there have been experiments to test dogs' ability to sniff out cancer.
For example, in 2010, a scientific meeting of the American Urological Association learned how researchers in Paris had trained dogs to sniff out prostate cancer. They showed the dogs could detect certain prostate cancer cell-derived volatile organic compounds (VOCs) in urine.
However, as more research has been done using dogs, so scientists have noticed a lot of variation in their performance between and during studies, so their findings have limited application.
A more promising avenue is the growth of labs working on the electronic equivalent of sniffer dogs - artificial olfaction or electronic nose technology. For instance, in 2012 we were taken behind the scenes of an electronic nose lab at the California Institute of Technology, and learned how investigators in that lab foresee that one day we will be using smartphones to sniff out diseases.
Electronic noses or 'eNoses' that analyze complex mixtures of gas molecules are already used in food and agriculture quality control, and in military applications.
Exhaled air is a 'problematic sampling material'
eNoses are already being investigated for medical use, including early detection of cancer from exhaled air, says lead investigator Dr. Niku Oksala, of the Department of Surgery in the School of Medicine at the University.
"However, exhaled air is a problematic sample material since it requires good cooperation and technique from the patient and immediate analysis," notes Dr. Oksala, who is also of the Department of Vascular Surgery, Tampere University Hospital.
He points out that urine, on the other hand, is simple to obtain and easy to store, and more feasible for use in clinical practice. Plus, he says:
"Preliminary data suggested that detection of urologic malignancies from urine headspace was possible. Our own preliminary results on prostate cancer cells encouraged us to launch this prospective clinical study."
For their study, he and his team used an eNose containing a cluster of non-specific electronic sensors. When the device is exposed to a sample, it produces a profile of gas molecules, or what is known as a "smell print." The model they used is the ChemPro 100, made by Environics Inc., based in Mikkeli, Finland.
They tested the eNose on 50 patients with biopsy-confirmed prostate cancer and 15 patients with BPH. All the participants underwent surgery and gave urine samples before surgery. Those with BPH also gave samples 3 months after surgery for use as a pooled control sample population.
eNose results on a par with the PSA tests
The results showed the eNose, which analyzed molecules in the urine headspace, was able to discriminate prostate cancer from BPH with a sensitivity of 78% and a specificity of 67%, notes the team.
Dr. Oksala says the eNose results were a par with those published for the PSA test, and moreover they are "achieved rapidly and in a completely noninvasive manner."
"PSA is known to correlate positively with prostate volume, which is a potential source of diagnostic error when comparing prostate cancer with benign disease," explains Dr. Oksala, who adds:
"According to our current analysis, prostate volume did not affect the eNose results, potentially indicating high specificity of our sensor array to cancer."
The team found no correlation between eNose signal and size of the tumor, and suggests further studies should now be done to improve the technology and identify the molecules behind the distinct odors.
Written by Catharine Paddock PhD