PC-3 human prostate cancer cells.
A test commonly used in breast cancer has been found to also identify which patients with aggressive prostate cancer will benefit from hormonal therapy, according to a study led by scientists at UC San Francisco and the University of Michigan.
While hormone therapy has been used successfully to treat many prostate cancer patients, until now, researchers have been unable to predict which patients would benefit from early initiation of this therapy following surgery. The study, conducted by a team of researchers at 11 medical centers nationwide and in Canada, demonstrates the first new way to select the best treatment for specific patients.
In the study, which appears today in the journal JAMA Oncology, the researchers divided prostate tumors into three subtypes based on genetic patterns. Their results reveal that starting hormone treatment after surgery prevents the spread of the tumor in only one of the three types, known as luminal B, a particularly aggressive form that affects about one-third of those with the disease.
Hormone therapy carries significant side effects, so knowing which patients are likely to benefit from it can focus treatment on the right patients at the appropriate time, while sparing the others of increased risk of fatigue, sexual dysfunction, osteoporosis, diabetes and other conditions.
If confirmed, patients with the luminal B subtype could be selected for early initiation of hormone therapy, which would allow for treatment intensification for patients most likely to benefit from it, said Felix Feng, MD, a radiation oncologist with UCSF Health and a senior author of the study.
“We’ve clearly shown that there are different molecular subtypes of prostate cancer and that a test widely used in breast cancer can also potentially be used to help individualize therapy for prostate cancer patients as well.” said Feng, a UCSF associate professor of Radiation Oncology, Urology, and Medicine, who specializes in the treatment of high-risk, aggressive prostate cancers. He is also a member of the UCSF Helen Diller Family Comprehensive Cancer Center.
The hormone treatment is known as androgen-deprivation therapy, or ADT. Just as estrogen has been found to promote breast cancer growth, male sex hormones called androgens – notably testosterone – stimulate prostate cancer. As in breast cancer treatment, depriving cancer of the critical sex hormone can starve some prostate tumors.
The test, called PAM50, has been used for over a decade to identify which breast cancers are the best candidates for hormone treatment. But no such screen has been available for prostate cancer, Feng said. The new research shows that PAM50 can also distinguish between the three prostate cancer subtypes.
“Ultimately, our goal is to find the right treatment for the right patient at the right time,” said Feng. “Using the PAM50 test may allow us to take the first step towards this goal, in the setting of hormone therapy for prostate cancer patients treated with surgery.”