Drug developed to treat women with inherited cancers similarly beneficial for treating prostate cancer

A drug originally developed to treat women with inherited cancers has proven to be similarly beneficial to men with advanced prostate cancer. The major clinical trial, led by experts at the Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust is the first to show the benefits of "precision medicine" – treatment matched to the particular genetic characteristics of the tumour – when attacking prostate cancer.

The drug in question, olaparib, was beneficial to at least a third of patients with prostate cancer in the trial known as TOPARP-A. A total of 49 males with advanced prostate cancer were included in the test and treated with olaparib – 16 of them responded positively to the treatment as it stopped cancer growth, generated lasting falls in prostate specific antigen (PSA) levels and lessened the amount of tumour cell counts in the blood.

The trial also found that around 30% of men with advanced prostate cancer had tumours that had repair defects in their system, which the olaparib responded even better to. Some 14 of the 16 patients had terminal prostate cancer with limited options on how to treat the affliction, but the drug controlled the disease for longer than expected, according to the study published in the New England Journal of Medicine.

Trial chief investigator Professor Johann de Bono, head of drug development at the Institute of Cancer Research, London, and The Royal Marsden NHS Foundation Trust, said: "Our trial marks a significant step forward in the treatment of prostate cancer, showing that olaparib is highly effective at treating men with DNA repair defects in their tumours. It also proves the principle that we can detect prostate cancers with specific targetable mutations using genomic sequencing to deliver more precise cancer care by matching treatment to those men most likely to benefit."

The success of this trial has led researchers to begin TOPARP-B – the second part of the trial where only men who have prostate cancer with detectable DNA mutations will receive olaparib.

'Cutting-edge genomic sequencing'

Study co-leader Dr Emma Hall, deputy director of the Cancer Research UK-funded Clinical Trials and Statistics Unit at The Institute of Cancer Research, London, which co-ordinated the study, said: "This phase II clinical trial combined a highly targeted cancer drug with cutting-edge genomic sequencing.

"We showed that a subset of men whose tumours had mutations in their DNA repair machinery responded particularly well to treatment with olaparib. The next trial includes only men with these mutations in their tumours, with the aim of proving that olaparib is highly effective for them."

Dr William Nelson, co-vice chair of the SU2C Scientific Advisory Committee and director of the Sidney Kimmel Comprehensive Cancer Center at Johns Hopkins in Baltimore, Maryland, said: "Understanding the link between prostate cancer and DNA repair mutations is incredibly important for patients and their families. We can identify prostate cancer patients who will benefit from drugs like olaparib and also help men and their families better understand their genetic risk of metastatic prostate cancer, just as women with BRCA mutations do for breast and ovarian cancer."