What is Prostate Cancer?

Prostate cancer is a disease in which small tumors develop in the prostate, a gland in the male reproductive system. It occurs when cells of the prostate mutate and begin to multiply uncontrollably.

Prostate cancer is the most commonly diagnosed non-skin cancer in North America and the third most common cause of cancer death in men. Every year an estimated 250,000 new cases of prostate cancer are diagnosed in North America and over 30,000 men die from the disease. It is estimated that one in 10 men in United States will have prostate cancer diagnosed in his lifetime [1].

Prostate Cancer Diagnosis

The two most common screening tools for detecting prostate cancer are prostate specific antigen (PSA) test and the digital rectal exam (DRE).

The PSA test measures the blood level of PSA, a protein produced by the prostate gland and released into the bloodstream. When the prostate grows in size (such as in benign prostate hyperplasia, or BPH), or when prostate cancer grows, more PSA is produced and released into the bloodstream.

PSA levels under 4 ng/mL are usually considered "normal”, between 4 and 10 ng/mL are "intermediate”, and over 10 ng/mL are usually considered "high”. However, the PSA test has limitations in that approximately 15% of men with prostate cancer have PSA levels below 4.0ng/ml, within “normal” limits [2]. In addition, there is no PSA value below which a man can be assured that he has no risk of prostate cancer.

The DRE is a procedure whereby the examiner inserts a gloved, lubricated finger into the rectum to check the size, shape, and texture of the posterior side of the prostate. Areas that feel irregular, hard or lumpy indicate that cancer may be present. The limitation with the DRE is that only the back wall of the prostate gland is palpatable, so any abnormalities located in the middle or front part of the gland cannot be felt. As well, the outcome of the DRE relies greatly on subjectivity of the examiner’s experience and patient’s sensation. The DRE has a reported sensitivity of 55%-68% in asymptomatic men and a positive predictive value of 6% to 33% [3].

Both the DRE and PSA tests have been used by physicians for many years, but have often been criticized for their lack of sensitivity and specificity for predicting prostate cancer. Most clinicians, therefore, have adopted the strategy of performing both tests, and the two results together increase the predictive value. However, because of the significant risk of prostate cancer, prostate biopsy is currently recommended for all men who have DRE abnormalities, regardless of the PSA level.

A biopsy is an invasive procedure in which tissue samples are taken from the prostate via the rectum, often under the guidance of ultrasound imaging. The tissues are then examined under microscope to determine whether it is healthy or cancerous.

The Gleason grading system is used to assign a “grade” (from 1 to 5) to prostate cancer. "Low-grade" cancer cells are more like normal cells, whereas "high-grade" cancer cells have little similarity to normal ones.

NIRS DRE™ Technology for Prostate Cancer Imaging

Because of the low predictive value of the current tests, there is a need for innovative technologies to improve the reliability of prostate cancer screening. Urodynamix is developing NIRS DRE™ - a minimally invasive diagnostic device to be used with the digital rectal examination (DRE).

NIRS DRE™ is based on the fact that cancerous tissue is associated with overgrowth of blood vessels (hypervascularity) and increased blood flow.   It uses near infrared spectroscopy (NIRS) technology to detect hemodynamic status (blood flow and composition of oxygenated and de-oxygenated hemoglobin), which differs in healthy tissue vs. cancerous tissue to aid in the detection of prostate cancer. 

NIRS DRE™ may increase the sensitivity of the DRE and more accurately locate cancerous tissue within the prostate, allowing doctors to precisely target local treatments such as drugs, radiation seeds or probes that deliver energy to destroy cancer cells. This will help to reduce side effects most often associated with these treatments, such as ED and incontinence.

NIRS technology is expected to impact as many as 150 million men in the US, Europe and Japan who qualify for annual prostate cancer screening.

The NIRS DRE™ system consists of a finger-mounted NIRS sensor that transmits light into the prostate gland during the DRE and a detector that monitors blood flow in the various quadrants of the prostate gland. Physicians do not need to change their current DRE technique and the probe does not interfere with the physician's tactile sensation.

References:

[1] Godley PA. Prostate cancer screening: promise and peril—a review. Cancer Detection Prevention 1999; 23:316-24.

[2] Ian M. Thompson, Donna K. Pauler, Phyllis J. Goodman, Catherine M. Tangen, P.H., M. Scott Lucia, Howard L. Parnes, Lori M. Minasian, Leslie G. Ford, Scott M. Lippman, David Crawford, John J. Crowley, and Charles A. Coltman, Jr. Prevalence of Prostate Cancer among Men with a Prostate-Specific Antigen Level ≤4.0 ng per Milliliter. New England Journal of Medicine 2004; 350:22 (2239-2246).

[3] Rebecca Ferrini and Steven H. Woolf. Screening For Prostate Cancer in American Men. American College of Preventive Medicine Practice Policy Statement. http://www.acpm.org