Multigene Test Stratifies Prostate Cancer Aggressiveness

Rosemary Frei, MSc

October 2014, Vol 5 , No 8 - Prostate Cancer

Chicago, IL—The commercially available cell-cycle progression test known as Prolaris is helpful for stratifying risk for men with clinically localized prostate cancer and can help to modify treatment decisions for men with prostate cancer based on the aggressive nature of their tumor, according to a poster presented at the 2014 College of American Pathologists annual meeting by Michael K. Brawer, MD, Vice President of Medical Affairs, Urology, Myriad Genetic Laboratories, Inc, Salt Lake City, UT, and colleagues.

The Prolaris prognostic test, made and marketed by Myriad Genetics, Inc, involves a multigene panel that is calculated to reach the cell-cycle progression score. Previous studies funded by Myriad indicate that Prolaris scores strongly correlate with prostate cancer outcomes, such as disease-specific mortality, biochemical recurrence, and metastasis, whether the tissue samples are derived by prostatectomy or by needle biopsy (eg, Bishoff JT, et al. J Urol. 2014;192:409-414).

Dr Brawer and colleagues analyzed data from Myriad’s laboratory database for patients whose prostate biopsies underwent the multigene test and for whom clinicopathologic data were available. The score was calculated by “measuring the RNA expression of 31 cell-cycle progression genes normalized to 15 housekeeping genes,” Dr Brawer and colleagues noted.

The test was ordered by 787 physicians. The study set involved 3502 biopsy samples that yielded RNA of sufficiently high quality to undergo the multigene analysis. The test scores ranged from –2.9 to 3.4. Based on the test score, 38.7% of the men had a tumor that was less aggressive than was indicated by the clinicopathologic analysis, and 19.8% had cancer that was more aggressive than was indicated by the clinicopathologic analysis.

The highest proportion of cancer cases that were less aggressive or considerably less aggressive, according to the multigene test result, than clinicopathology (39.8%) were in the low-risk category of the American Urological Association (AUA) risk classification. The highest proportion of cases that were more aggressive or considerably more aggressive (29.7%) than indicated by the clinicopathology analysis were in the AUA high-risk category.

“Our studies have shown that for every 1-unit increase in Prolaris score, you double the risk of dying or failing treatment,” Dr Brawer told Value-Based Cancer Care. “Prolaris adds dramatically to the prognostic information.”

The investigators also analyzed surveys that had been completed by clinicians. In 198 (64.9%) of the 305 cases, the physicians reported changing the therapy based on the prognostic test results. This included 122 (40%) cases in which the clinicians decided to reduce the therapeutic burden and 76 (24.9%) cases in which they increased the burden. Furthermore, for 103 (32.7%) of 315 cases, the physicians thought that the prognostic score was moderately influential in their therapeutic recommendation. They reported that it was highly influential in 136 (43.2%) of 315 cases and very highly influential in 37 (11.8%) of 315 cases.

These results suggest that the multigene prognostic test can improve the risk stratification of patients with prostate cancer and may help to guide treatment decisions based on a more accurate risk score compared with other risk assessment tools, such as the Gleason score, the prostate-specific antigen level, or the clinicopathologic features alone.