Prostate Cancer

Background

An estimated 20 million men are screened for prostate cancer in the U.S. every year, and over 1 million are subsequently referred for biopsy. The decision to biopsy a patient’s prostate gland is made based on a digital rectal exam (DRE), and blood tests such as PSA (prostate specific antigen). Diagnosing prostate cancer can be difficult in some patients, particularly among those who have intermediate PSA values (4-10 ng/ml) with normal DRE. In such cases urologists must decide whether to perform a biopsy or place the patient on a program of active surveillance (expectant management). Because 75% of primary prostate biopsies show no cancer, avoiding unnecessary procedures would spare the patient pain and expense, and help to avoid potential procedure-related complications such as bleeding and sepsis (a serious, sometimes fatal infection of the blood). Additionally, biopsies do not always detect prostate cancer when it is present.

Even when prostate cancer is definitively diagnosed, the clinical staging by biopsy and Gleason scoring does not necessarily correlate with pathological staging. Approximately 50% of men whose disease is thought to be localized to the prostate prior to surgery actually have tumor extension beyond the prostate1, and a significant minority has already developed metastatic disease. Determining which tumors are aggressive based on biopsy and Gleason scores is particularly challenging with intermediate Gleason scores of 6-7. Specifically, within this "gray zone" for Gleason scores, the ability to predict disease aggressiveness(such as extracapsular extension, seminal vesicle invasion, and lymph node involvement) is limited, even when prostate biopsy results are coupled with other clinical parameters such as physical exam and PSA levels.The significant unmet clinical needs in prostate cancer detection and risk assessment are the driving force behind Metabolon’s efforts to develop better diagnostics in this area.

Prostarix™ DRE Urine Test

Metabolon’s prostate cancer detection test is based on detecting a unique metabolic signature from the pellet, which is spun down from a small urine sample taken post-DRE. This highly accurate test can be performed prior to the primary biopsy (to inform the decision to perform a biopsy), at the time of biopsy, or after a first-negative biopsy (to inform the decision to perform a second biopsy). The test can also be used during the expectant management process. Because Metabolon’s test is non-invasive, it provides additional clinical information to guide physician decision-making and improve patient management while minimizing risk to the patient and the added expense from an unnecessary biopsy.

Prostarix™ Prostate Biopsy Assessment

Biopsy is the gold standard for diagnosing prostate cancer, and the histopathology of the patient’s biopsy is one factor used to determine whether the cancer is at an early or advanced stage. Metabolon’s test measures a panel of metabolites in the prostate biopsy tissue that enables the physician to more accurately determine whether the patient’s tumor is aggressive. This test is performed on fluid in which prostate biopsy cores are soaked prior to processing by the pathologist. Metabolon’s proprietary process for metabolite extraction from biopsy cores does not compromise the biopsy tissue or alter tissue morphology. The Prostarix™ Prostate Biopsy Assessment test gives clinicians valuable information about the aggressiveness of their patient’s prostate cancer, enabling improved decision-making in the clinical management of the patient’s disease.

1 Partin AW, Kattan MW, Subong EN, Walsh PC, Wojno KJ, Oesterling JE, et al. Combination of prostate-specific antigen, clinical stage, and Gleason score to predict pathological stage of localized prostate cancer. A multi-institutional update. JAMA 1997;277:1445-51