The research team was able to isolate cancer DNA in a patient’s bloodstream and determine which men with advanced prostate cancer were likely to benefit from treatment with a new class of drugs called poly (ADP-ribose) polymerase (PARP) inhibitors-specifically the drug olaparib.
By analysing the tumour DNA in blood samples from a small number of men closely, the researchers were also able to uncover genetic faults that might explain why treatment stopped working.
Scientists have developed a three- in-one blood test that can predict which prostate cancer patients are likely to benefit from a treatment and monitor the disease for drug resistance, an advance that may pave the way for more personalised precision therapies.
“We think it could be used to make clinical decisions about whether a PARP inhibitor is working within as little as four to eight weeks of starting therapy”.
De Bono added that the test can have a major impact not just on the treatment of prostate cancer, but it can also be adapted to pave way for precision medicine for patients diagnosed with other types of cancer. For patients with tumors deficient in homologous recombination fix, potential opportunities for treatment include platinum chemotherapy, poly (ADP) ribose polymerase (PARP) inhibitors, bipolar androgen therapy, and maybe immune checkpoint blockade therapy.
Patients whose cancer DNA blood levels were lowered by olaparib survived an average of 17 months compared with 10.1 months for those whose levels remained high.
The test targets specific gene mutations associated with the disease.
The drugs do not generally work on cancer cells with functioning BRCA genes, because these are primary DNA fix tools that make PARP unnecessary.
This type of precision drug is seen as the future of cancer medicine but because it is a targeted treatment, the drug does not work for everyone.
Cancer DNA dropped by nearly half in men who were responding to the drug.
They found that the cells acquired genetic changes that cancelled out the DNA fix defects making them susceptible to the drug.
Dr Aine McCarthy, senior science information officer at Cancer Research UK, said the blood test was an “exciting” development.
“This is another important example where liquid biopsies-a simple blood test as opposed to an invasive tissue biopsy-can be used to direct and improve the treatment of patients with cancer”, commented David Cunningham, Ph.D., director of clinical research at The Royal Marsden NHS Foundation Trust.
Cancer Research UK said the test could “greatly improve survival”.
Lynparza, which is already approved for ovarian and recently produced good results in breast cancer, is now in clinical development against prostate tumors.