Two new genetic tests may help better predict which prostate cancers are aggressive and need immediate treatment, and which do not need treatment right away, researchers say.
One test, called Prolaris and manufactured by Myriad Genetics, looks for specific genes that control a cancer cell's abilities to divide and multiply. Patients receive a score (between -3 and 3) that indicates how aggressive their cancer is.
The other test, called Oncotype DX Prostate Cancer Test and manufactured by Genomic Health, was released earlier this month and is also marketed as a test to predict prostate-cancer aggressiveness.
Both tests have the potential to reduce the overtreatment of prostate cancer. Many men with the disease undergo surgery or radiation therapy despite having low-risk cancers that likely would not have been fatal.
But experts say that although these tests do seem to help predict cancer outcomes, their usefulness to doctors and patients remains to be seen. Researchers still need to determine "how much added information these tests really provide, and how often it's going to really change how we manage a patient," said Dr. Judd Moul, director of the Duke Prostate Center in Durham, N.C.
In a review of five studies, researchers at Myriad found that the Prolaris test, in combination with standard methods of assessing prostate cancer — including the PSA test and the Gleason score — could better predict whether patients would die from prostate cancer than the PSA test and Gleason scorecould alone. (The PSA test measures blood levels of a protein called prostate-specific antigen, which is linked to prostate-cancer risk. The Gleason score grades prostate cancer on a scale from 2 to 10 based on how it looks under a microscope.)
A patient with a Prolaris score of 2 would have twice the risk of cancer spreading to other parts of the body compared with a patient with a score of 1, said Michael Brawer, vice president of urological medical affairs for Myriad. And a patient with a score of 0 would have half the risk of the disease spreading compared with a patient with a score of 1, Brawer said.
Prolaris, which is already available to patients, has been studied in about 3,000 men with prostate cancer, some of whom were tested after they underwent treatment, and some of whom were tested at the time they were diagnosed. The review of the five studies will be presented May 31 at the American Society of Clinical Oncology’s annual meeting in Chicago.
It's thought that up to 40 percent of prostate-cancer patients could take a watchful-waiting approach, also known as active surveillance, in which a patient is frequently checked, and the cancer is treated if it progresses. Currently, only about 10 percent of patients take this approach, according to the National Institutes of Health.
The Prolaris test could increase the number of patients who take the watchful-waiting approach by helping them better understand their risk of disease progression, Brawer said.
Other experts said it's not clear whether either genetic test could provide a benefit beyond a watchful-waiting approach.
Even if a man with a genetically aggressive cancer decided to undergo watchful waiting, it's not certain whether that approach would be harmful, said Dr. Andrew Vickers, a PSA researcher at Memorial Sloan-Kettering Cancer Center in New York and a study adviser to Genomic Health who has received payments from the company. If a man's cancer were to progress, it could be caught and treated with watchful waiting, without the need for genetic tests.
In addition, it's not certain whether the tests could help patients who have already undergone prostate-cancer treatment. The genetic tests may reveal that a patient is at risk for cancer recurrence, but doctors don't have a standard treatment to give prostate-cancer patients in these cases, said Dr. Manish Vira, of the Arthur Smith Institute for Urology, part of the North Shore-Long Island Jewish Health System in New Hyde Park, N.Y.
"The real question is, what do you do with the information from these tests?" Vira said.
Both tests are expensive, and are not always covered by insurance. The Prolaris test costs $3,400, and Oncotype DX costs $3,820.
Moul said he has ordered the Prolaris test a few times but that the price is a barrier for patients who aren't willing to pay out-of-pocket for the test.
Ronald Rogers, a spokesman for Myriad, said the company is working with insurance companies to expand reimbursement.
Ultimately, in order to tackle overtreatment, physician behavior needs to change, Vicker said. "Far too many men with prostate cancer are being treated unnecessarily," he said.