BRCA genes produce tumor-suppressor proteins. Everything else being equal, these proteins will help repair damaged DNA and so ensure that cells’ genetic material remains stable. The genes are prone to mutation, however, and when that happens, DNA materials might not get repaired. This often leads to cancer.

We tell you this because scientists at The Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust have just found a way to use this cellular design flaw that could transform treatment of advanced prostate cancer.

The researchers have created a blood test that targets and monitors this “cancer DNA” in three ways. First, it allows doctors to identify which patients with advanced prostate cancer were likely to benefit from treatment with PARP inhibitors. These are drugs which bind to that particular enzyme which feeds many forms of cancer, including prostate.

Secondly, the test can be used to analyze DNA in the blood after treatment had started. This allows doctors to switch people who were not responding to alternative therapy in as little as one to two months.

Thirdly, the new test can be used to monitor a patient’s blood throughout treatment. This enables doctors to quickly discern any signs that the patient’s cancer is evolving genetically and might be becoming resistant to the drugs.

The researchers collected blood samples from 49 men at The Royal Marsden with advanced prostate cancer enrolled in a phase II clinical trial of PARP inhibitor olaparib. Past work with olaparib showed This research could open the door for olaparib to become a standard treatment for advanced prostate cancer, by targeting the drug at the men most likely to benefit, picking up early signs that it might not be working, and monitoring for the later development of resistance.

"Not only could the test have a major impact on treatment of prostate cancer, but it could also be adapted to open up the possibility of precision medicine to patients with other types of cancer as well,” said Professor Johann de Bono, Regius Professor of Cancer Research at The Institute of Cancer Research, London, and Consultant Medical Oncologist at The Royal Marsden NHS Foundation Trust.

The study has been published in the journal Cancer Discovery.