Prolaris, a genetic test developed by Myriad Genetics to help predict the aggressiveness of prostate cancer, can accurately identify prostate cancer patients with low-risk disease who may safely opt for active surveillance, a study found.
Among 547 men who choose active surveillance, only two experienced tumor progression during the study, corresponding to an event-free survival at five years of 98.5%.
The study, “Clinical outcomes in men with prostate cancer who selected active surveillance using a clinical cell-cycle risk score,” was published in the journal Future Medicine.
Prostate cancer is the most common cancer among men, but a great number of cases will remain dormant and not progress to cause significant disability or risk of mortality. In these cases, active surveillance — an approach that consists of actively monitoring the cancer to detect progression before starting any treatment — is an accepted alternative to treatments that can carry significant side effects.
The American Urological Association and the National Comprehensive Cancer Network (NCCN) guidelines consider active surveillance to be the standard approach for low-risk prostate cancer.
Clinical exams to assess prostate cancer risk, however, can underestimate the number of patients who could benefit from active surveillance. Researchers estimate that only 40% to 50% of low-risk patients are selected for this approach, leading to over-treatment of men with low-risk disease.
“Historically, active surveillance has been underutilized in men with low-risk prostate cancer with fewer than half selecting AS for their initial treatment, resulting in the overtreatment of many men,” Behfar Ehdaie, a board-certified urologist at Memorial Sloan Kettering Cancer Center and the study’s lead author, said in a press release.
Prolaris is a genetic test that aids clinicians in predicting the aggressiveness of prostate cancer when used in combination with a person’s Gleason score — a measure of prostate cancer aggressiveness based on how cells look under a microscope — and prostate cancer antigen (PSA), a biomarker or prostate cancer.
The test uses tissue collected in a biopsy done to confirm a cancer diagnosis.
In this study, researchers examined 664 prostate cancer patients with had low-risk disease according to both the Prolaris test and NCCN guidelines. Of them, 547 (82.4%) were placed on active surveillance, while 117 (17.6%) received definitive treatment within six months of diagnosis. Patients were followed for up to five years.
Both patient groups were very similar in their characteristics, but those who received more radical treatments had more aggressive cancers than those on active surveillance.
Over a median of 2.2 years, five men experienced disease progression, corresponding to a five-year event-free survival of 97.8% for the total study population. Two were on active surveillance, placing that group’s five-year event-free survival at 98.5%.
Less than 25% of patients on active surveillance received further treatment during the study’s course, with the most common being radical prostatectomy (removal of prostate gland and nearby tissue) in 60.9% of cases and radiation therapy in 26.3%.
The proportion of patients on active surveillance dropped to 91.2% at year one, 69.6% at three years, and 65.2% at four years.
“[T]he majority of men who choose active surveillance as their initial treatment remained on active surveillance four years later, underscoring the clinical utility of the Prolaris test,” said Todd Cohen, vice president of Myriad Urology Medical Affairs and a board-certified urologist.
Among patients deciding to end active surveillance in favor of more definitive treatment, 23.3% did so due to an increasing Gleason scores. Patient choice was the most frequent reason given to quit active surveillance.
“Collectively, the data presented here suggest that using the CCR [cell cycle risk] score in prostate cancer risk assessment can safely increase the selection of AS among appropriate men, compared with clinicopathologic criteria alone,” the researchers concluded.
“These findings should give doctors confidence that active surveillance is a safe, long-term option for men with low-risk prostate cancer and who have a low Prolaris test score,” Cohen said.
Of note, five of the study’s 14 researchers were Myriad employees at the time of this research.