Electronic nose sniffs out prostate cancer in urine samples
A novel noninvasive technique can detect prostate cancer using an electronic nose. In a proof of principle study, the eNose successfully discriminated between prostate cancer and benign prostatic hyperplasia (BPH) by sniffing urine headspace (the space directly above the urine sample). Results using the eNose were comparable to testing for prostate specific antigen (PSA) levels.
Prostate cancer is the second most common cancer in males and one of the leading causes of cancer death. The heterogeneity of prostate cancer makes it difficult to diagnose and predict tumor progression. Both of the current cornerstones of diagnosis, digital rectal examination (DRE) and PSA levels, have limitations, and ultrasound-guided biopsies are costly, uncomfortable for the patient, and have a risk of infection.
Additionally, significant numbers of diagnosed prostate cancers are of low grade and will not cause symptoms or disease-specific mortality. Therefore, aggressive treatment can lead to decreased quality of life without extending the patient's life. Thus, novel diagnostic tools are needed.
In the 1980s incidental reports of dogs detecting cancer in their owners sparked a number of experimental studies that confirmed that trained sniffer dogs can detect cancer. However, variations in dogs' performance have led to limited applications for these findings. A more promising development is the growth of sensor technology, generally called artificial olfaction, which has led to the invention of numerous new types of olfactory electronic sensors.
eNoses are best suited for qualitative analysis of complex gaseous mixtures of molecules, and are routinely used in food and agricultural quality control and military applications. The eNose used in the current study is a device that consists of a cluster of nonspecific sensors. When the device is exposed to the sample, it produces a profile or a smell print.
"eNoses have been studied in various medical applications, including early detection of cancer, especially from exhaled air," says lead investigator Niku KJ. Oksala, MD, PhD, DSc, of the School of Medicine, University of Tampere, and of Tampere University Hospital, Finland. "However, exhaled air is a problematic sample material, while urine is simple to attain and store, and is therefore more feasible in clinical practice. Preliminary data suggested that detection of urologic malignancies from urine headspace was possible."
The ChemPro 100–eNose (Environics Inc.; Mikkeli, Finland) was tested on 50 patients who had a prostate cancer diagnosis confirmed by biopsy, and 15 patients with BPH. Both groups were scheduled for surgery.
The patients provided urine samples before surgery, and those with benign disease also provided samples 3 months after surgery to be used as a pooled control sample population. Patients with prostate cancer underwent robotic-assisted laparoscopic radical prostatectomy, and the benign disease group underwent transurethral resection of the prostate.
Results with the eNose confirmed that, using urine headspace, the eNose is able to discriminate prostate cancer from BPH. The findings were published in the Journal of Urology (2014; doi:10.1016/j.juro.2014.01.113).