Pioneering prostate cancer drug abiraterone significantly extends the lives of men with advanced prostate cancer if given prior to administering chemotherapy, as shown in the results of a major phase III clinical trial.

The results, published in Lancet Oncology (2015; doi:10.1016/S1470-2045(14)71205-7), demonstrated that men with advanced, aggressive prostate cancer lived more than 4 months longer on average if they received abiraterone before chemotherapy than if they did not.

The trial, led in the UK by Professor Johann de Bono, MD, PhD, of The Institute of Cancer Research, London, United Kingdom, and The Royal Marsden National Health System (NHS) Foundation Trust, could fill an important gap in previous evidence for abiraterone’s effectiveness prechemotherapy.

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An earlier analysis, published in 2013, showed that abiraterone taken before chemotherapy increased the time before a man’s cancer progressed but did not prove an overall extension in life.

The new results coincide with the publication of a second new international study of patients in the same trial, also led in the UK by researchers at The Institute of Cancer Research (ICR) and The Royal Marsden.

That study, published in Clinical Cancer Research (2015; doi:10.1158/1078-0432.CCR-14-1961), shows it is possible to identify a subgroup of men with very aggressive prostate cancer who may benefit particularly strikingly from abiraterone before chemotherapy.

The first new study compared the average survival of 354 men given abiraterone before moving on to chemotherapy with 387 men who received a placebo instead. Both groups also received low-dose prednisolone, a treatment used alongside abiraterone.

The men who received abiraterone lived significantly longer than those who did not: an average of 34.7 months, compared with 30.3 months. The trial results also further support the favorable safety profile of abiraterone, with relatively few patients experiencing severe side-effects.

The second new study of men from the same trial showed that a subgroup of patients with a very aggressive form of prostate cancer may benefit the most from treatment with abiraterone.

The researchers cross-referenced data on how well 348 men on the trial responded to either abiraterone or a placebo, as defined by a halt in the progress of their cancer, with a detailed genetic analysis of their tumors.

They looked in particular at whether changes to the ERG gene, which are often associated with faster cancer progression, correlated with abiraterone response.

They found a clear link between major ERG mutations and response to abiraterone. Although abiraterone improved survival generally regardless of ERG mutations, a subset of patients with the most pronounced mutations to the gene, accounting for 15% of the men studied, responded particularly well.

These men lived for an average of 22 months without their disease progressing, compared with 5.4 months for men with the same ERG status who received a placebo.

Both studies were funded by Janssen, the manufacturer of abiraterone.