International study of advanced prostate cancer genome finds abundance of potential targets for drug therapy

The first major effort to canvas the genomic landscape of advanced prostate cancer has revealed that many patients may carry some type of genetic abnormality that can be targeted with existing or potential drugs.

The finding, reported today by a Stand Up to Cancer-Prostate Cancer Foundation Dream Team in the May 21, 2015, edition of the journal Cell, is based on an analysis of tumor samples from 150 men with metastatic prostate cancer that no longer responded to standard hormone-blocking therapy. Eight institutions from the United States and Europe contributed tumor samples to the project.

“This study provides a strong argument that the genomics driving advanced prostate cancer is fundamentally different than primary prostate cancer, and that knowledge of these genomic differences may be immediately clinically actionable for patients with advanced disease,” said Eliezer Van Allen, MD, of Dana-Farber Cancer Institute, a first author of the study.

While previous studies have surveyed the genomic characteristics of tumors confined to the prostate gland, the new study is the first to focus on metastatic hormone resistant prostate cancers, which can be difficult to treat because they often develop resistance to standard treatments.

The researchers found that nearly all the tumors had at least one genetic aberration known to drive cancers. The most common, found in nearly two-thirds of the samples, were abnormalities in genes responsible for the androgen receptor – a cell structure that sends growth signals in response to the male hormone androgen. This wasn’t a surprise since the hallmark of castration-resistant disease is that it no longer responds to conventional androgen-blocking therapies. But many other aberrations were found as well.

About a quarter of patients had mutations in the DNA repair genes including BRCA1 or BRCA2 genes, which are known to increase the risk of breast and ovarian cancer. Drugs known as PARP inhibitors have already been approved for BRCA-positive ovarian cancer, suggesting that PARP inhibitors may prove effective in prostate cancers with this type of aberration.

In addition, the researchers found that 8 percent of patients had an inherited genetic alteration. This suggests that genetic counseling may be appropriate for patients with prostate cancer.