Men with particularly aggressive prostate cancers can be treated more effectively by combining an existing targeted medicine with an experimental drug, new research suggests.
Using both medications extended the time before prostate cancers progressed and spread further in men whose tumours lacked a gene known as PTEN.
This is one of the most commonly deleted tumour suppressor genes – which often function to restrain inappropriate cell growth and division – in cancer.
Researchers assessed the efficacy of the targeted hormone drug abiraterone – standard medicine for many men with advanced prostate cancer – together with a new drug called ipatasertib in men with advanced prostate cancer who had received no prior treatment.
The international phase three trial, known as the IPATential150 study, took place across 200 sites in 26 countries and involved 1,101 men, of whom 521 had tumours that lacked a fully functioning PTEN gene.
Funded by Roche, the trial found that giving ipatasertib plus abiraterone as a first-line treatment reduced the risk of death or cancer progression in those patients by 23% compared with abiraterone alone.
Around half of men with advanced prostate cancer have tumours with faulty PTEN genes – more than 10,000 men per year in the UK – meaning they could potentially benefit from the combination treatment if it were to be approved.
Researchers say that men with tumours lacking the gene tend to have a particularly poor prognosis, but the new results could open up the combination treatment as a new targeted approach to keep patients healthy for longer.
Among patients with tumours that lacked PTEN, 61% of those who received the combination saw their tumour get smaller, compared with 39% for those who took abiraterone on its own.
Additionally, 19% of those taking the combination had a complete remission – meaning no sign of the disease was found – compared with 6% for those taking abiraterone only, the study published in The Lancet found.
The drug combination works by simultaneously switching off two powerful growth signals that fuel prostate cancer.
However, researchers, led by The Institute of Cancer Research, London (ICR), and The Royal Marsden NHS Foundation Trust, say longer follow-up will be needed before the combination can get regulatory approval or be accessed on the NHS.
Study leader Johann de Bono, professor of experimental cancer medicine at the ICR and consultant medical oncologist at The Royal Marsden NHS Foundation Trust, said: “We have shown that combining an existing and a new drug to attack cancer on two different fronts can keep men with prostate cancer healthier for longer.
“The findings offer a promising new treatment option for patients with a common and aggressive type of prostate cancer, and could eventually change clinical practice for these men.
“PTEN is one of the most commonly deleted genes in prostate cancer, so this study offers hope to many patients.”