Not too long ago, prostate-cancer genetics didn’t mean much to patient care. But in recent years, the landscape of therapy has transformed as researchers have discovered links between multiple genes and aggressive tumors.
Now, as a hematologist-oncologist explained to attendees at an Association of VA Hematology/Oncology regional meeting in Detroit, genetic tests can guide treatment for some—but not all—men with prostate cancer.
For patients with mutations, appropriate supplemental medications “can improve overall outcomes and have a long-standing impact on patients” said Scott J. Dawsey, MD, of the John D. Dingell Veterans Affairs Medical Center in Detroit in an interview following the AVAHO meeting, which focused on the management of prostate cancer.
As Dawsey explained, about 10% of patients with prostate cancer appear to have genetic mutations, although the exact percentage is unclear. The mutations are especially common in metastatic forms of prostate cancer. They’re estimated to be present in 11.8%-16.2% of those cases.
While these proportions are relatively small, the number of overall prostate-cancer cases with mutations is large due to the high burden of the disease, Dawsey said. Prostate cancer is by far the most common cancer in men, and estimated 299,010 cases will be diagnosed in the United States this year.
According to Dawsey, genetic mutations seem to boost the risk of more aggressive disease—and the risk of other malignancies—by disrupting DNA repair. This process can lead to even more mutations that may “make the cancer behave and grow more aggressively.”
But not all prostate cancer patients need to undergo genetic testing. Dawsey urged colleagues to figure out which patients should be tested by consulting National Comprehensive Cancer Network (NCCN) guidelines and the newly updated US Department of Veterans Affairs (VA) prostate cancer clinical pathway .
The two sets of recommendations agree on germline testing in patients with cases that are metastatic, very high risk, and high risk. Lower-risk cases should only be tested if patients meet family history criteria. The sets of guidelines also recommend somatic testing in patients with metastatic cancer.
In addition to providing guidance about treatment, genetic test results can have implications regarding other potential malignancies that may affect patients, Dawsey said. The results may also have implications for cancer risk in family members.
Several drugs are now available for patients with genetic mutations, including checkpoint inhibitors and PARP inhibitors. The drugs, which have unique mechanisms of action, are given in addition to standard prostate cancer treatments, he said.
“If a patient doesn’t have one of these genetic changes,” he said, “these drugs aren’t an option.”
A long list of drugs or combinations of drugs are in clinical trials, including the poly(adenosine diphosphate–ribose) polymerase (PARP) inhibitors olaparib, abiraterone, and niraparib and the checkpoint inhibitors nivolumab and cemiplimab.
The drugs generally improve response rates and progression-free survival, Dawsey said, and patients are generally able to tolerate them. In regard to which drugs to choose, he suggested consulting the and NCCN guidelines and the VA oncology clinical pathway for prostate cancer.