Australian cancer researchers have discovered a biomarker in the blood for metastatic prostate cancer that can predict whether a patient will respond to chemotherapy. The study1, which is a world-first phase 3 investigation of response to chemotherapy in patients with the biomarker, is a unique collaboration between clinicians and scientists at Chris O’Brien Lifehouse and Garvan Institute of Medical Research.

Patients with metastatic, castration-resistant prostate cancer (mCRPC) were assessed using a blood test to detect the presence of a methylated copy of the glutathione s transferase gene (mGSTP1). The mGSTP1 biomarker was detected in the blood of 81% of patients before treatment. After two cycles of chemotherapy drug docetaxel, the blood tests were performed again. In 53% of cases, the biomarker was no longer detectable. The absence of detectable mGSTP1 was a reliable indicator of both longer overall survival and slower disease progression, providing an accurate guide for treatment decisions.

Prostate cancer is the most commonly diagnosed cancer for men in Australia, with an estimated 3,500 deaths from the disease in 2018.

Professor Lisa Horvath, director of medical oncology at Chris O’Brien Lifehouse, says of the discovery, “This significant advance in personalized cancer treatment can provide clinicians with reliable information for making decisions that ensure the patient is getting the most effective treatment for them and potentially avoiding unnecessary treatment.”

The mGSTP1 gene was first identified as a prostate cancer specific biomarker 20 years ago by Professor Susan Clark, Head of Genomics and Epigenetics, Garvan Institute and her colleagues at CSIRO. Professor Clark says, “I am immensely proud of this collaborative Australian discovery which will allow us to tailor the most appropriate treatment to a patient, based on the genetic makeup of the cancer.”

Researchers involved in the study are looking forward to conducting further clinical trials of the biomarker which will potentially result in the one of the first licenced epigenetic2 biomarkers for prostate cancer.