The study is a proof of principle that tests for cancer DNA in the bloodstream can be used to detect drug resistance mutations - allowing patients who will not benefit from one drug to be given an alternative treatment instead.
Researchers analyzed 274 blood samples from 97 patients using state-of-the-art DNA sequencing techniques.
They found that mutations in a gene called the androgen receptor (AR) predicted resistance to the prostate cancer drug abiraterone, and that patients with these mutations had poorer survival. The new study is published in the prestigious journal Science Translational Medicine.
Abiraterone is now standard treatment for men with advanced prostate cancer - but while it is highly effective in many patients, 30-60% do not respond. So researchers have been searching for a marker that will help predict in advance which men will benefit from the drug, and who should be given a different treatment.
Researchers discovered that men who harbor either a specific mutation or an increase in the number of copies of the AR gene, were 7.8 times less likely to have a reduction of more than 90% in their PSA levels, a widely used test to monitor the response of prostate cancer.
The study also found that in about 15% of men given abiraterone who did not have either mutation before starting treatment, this was acquired as the drug stopped working and appeared in the bloodstream several months before patients developed any symptoms.
"We are now planning a clinical trial involving up to 600 men in which we aim to prospectively show that men who are positive with our test have significantly greater benefit from chemotherapy in preference to abiraterone or similar drugs” said the author.