Gene flaws key to treating advanced prostate cancer?

May 22--When it comes to advanced prostate cancer, 9 in 10 patients carry a genetic anomaly that could guide doctors to the best treatment, according to a new study.

And that means cancer doctors should step up genetics testing -- something that isn't routinely ordered now or is limited to test only for certain well-known mutations, said University of Michigan's Dr. Arul Chinnaiyan, a cancer pathologist and a lead author of a paper that appears today in the scientific journal Cell.

By widening the search to a larger stretch of a patient's DNA, doctors may identify the cancer's vulnerability. And the earlier the better, Chinnayian said.

"The goal is to match the mutations with the therapy," he said.

The work adds to a growing understanding of the importance of precision medicine. It's an approach in which certain cancers are treated not so much on where they're found -- in the breast versus lung versus prostate, for example -- but by a tumor's genetic code.

In the latest paper, researchers mapped out the DNA of tumor samples from 150 men with metastatic castration resistant prostate cancer, an advanced cancer that has stopped responding to standard hormone-based therapies.

In many cases, those cancers had grown resistant to therapies that had worked initially.

Chinnaiyan, director of the Michigan Center for Translational Pathology, and Dr. Charles Sawyers, an oncologist at New York'sMemorial Sloan-Kettering Cancer Center, led the study that involved researchers from the U.S. and Europe.

They found a clear and "actionable" genetic mutation in most cases, meaning that there are treatments available to address the genetic aberrations, and thus the cancers.

Nearly two-thirds of the tumors showed aberrations in the androgen receptor. That's not surprising. Advanced prostate cancer often stops responding to drugs that lower levels of androgen, a male sex hormone. Additionally, 14% of patients had a mutation in the BRCA1 or BRCA2 gene, a genetic misfire infamous for its role in breast cancer.

Some patients had both mutations, Chinnaiyan said. Other patients had other genetic anomalies.

Previous studies have found few genetic alterations that can be addressed in localized prostate cancer.

Because the latest work focused on this advanced, treatment-resistant cancer, the cases brought into better focus the genetic mutations that make some cancers resistant to treatment, Some of those mutations may have been present before the cancer was discovered; others most likely evolved as a result of the treatment, Chinnaiyan said.

As part of the continuing work, researchers will continue sequencing and treating a total of at least 500 patients, a process that could take several years.

Contact Robin Erb: rerb@freepress.com or 313-222-2708. Follow her on Twitter @Freephealth.

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