Blood test predicts the best treatment for prostrate cancer

A new study is one of the first to demonstrate that a blood test could predict how patients would respond to treatment. Patients testing positive for AR-V7 may respond better to certain treatments.

The study, an international collaborative effort, with researchers working from the Lawson Health Research Institute, Memorial Sloan Kettering Centre, the Royal Marsden and Epic Sciences, determined that a blood test can envisage the response of advanced prostrate cancer patients to specific treatments.

Molecular diagnostics company Eric Sciences developed a liquid biopsy test which examines circulating tumour cells (CTCs) in blood samples of prostrate cancer patients deciding whether to change to chemotherapy from hormone-targeting therapy.

CTCs are cancer cells which enter the bloodstream, invading other areas of the body enabling the spread of cancer. The test identifies whether a patients CTCs contain a protein called AR-V7 in the nucleus of the cell. The team investigated whether the presence of this protein predicted the most suitable treatment for the patient – the one which would prolong the life of the patient for the longest.

The study showed that patients testing positive for AR-V7 responded better to taxane-based chemotherapy, whereas those who tested negative responded better to the hormone-targeting therapy with androgen-receptor signalling (ARS) inhibitors.

A scientist at Lawson and Chair, Department of Anatomy and Cell Biology at Western University’s Schulich School of Medicine and Dentistry, Dr Alison Allan said, “The study focused on a critical decision point when patients and their oncologists are choosing what therapy to pursue next.

“We are addressing a critical unmet need by validating that a blood test or liquid biopsy can be used to select a therapy most likely to extend a patient’s life.”

Participants for the research included 142 patients with advanced prostrate caner, who had already undergone at least one round of hormone-targeting therapy without success and were working with their oncologist to decide which therapy to use next; another type of hormone-targeting therapy or chemotherapy.

Dr Allen explains, “ARS inhibitors are the preferred first line of treatment because they target the hormones that provide the fuel for prostate cancer cells to grow. However, at some point, cancer cells can figure out a way to survive without this fuel and become resistant to ARS inhibitors, in many cases through production of the AR-V7 protein. That’s why chemotherapy is sometimes used as a second line therapy.”

The future goal of the team is to assess patients using this tool earlier in the process, in order to determine the optimal therapy from the very beginning. The team also look to create different versions of this blood test in order to test for treatments for other cancers.

The study was published in JAMA Oncology.