1: Earlier abiraterone improves survival for men with advanced prostate cancer: results from STAMPEDE and LATITUDE
The results of two trials presented at ASCO (and published concurrently in the New England Journal of Medicine) show that adding abiraterone plus prednisone to androgen deprivation therapy (ADT) prolongs both progression free and overall survival.
The first of these, an arm of the UK-based STAMPEDE study, was a phase 3, randomised, open label trial. The majority of men were newly diagnosed and they had either metastatic (n=1002; 52%) or non-metastatic (n=915; 48%) disease. Men in the treatment arm (abiraterone + prednisone + ADT) had a 3 year survival of 83% compared to 76% for men receiving ADT alone (HR 0.63; [CI] 0.52-0.76; p<0.001). While there were benefits for men with both metastatic and non-metastatic disease (HR 0.61 and 0.75, respectively), most of the deaths occurred in the metastatic group and further follow up will be required to confirm the effect of abiraterone for men with non-metastatic disease.
The second study, LATITUDE, a double-blind, phase 3 RCT, with a median follow up of 30.4 months, had remarkably similar findings. Median overall survival was significantly longer in the abiraterone treatment group (n=597) compared to placebo control (n=602) (not reached vs. 34.7 months. HR 0.62; [CI] 0.51-0.76; p<0.001), as was radiographic progression-free survival. As expected, in both trials there were more serious adverse effects (grade 3) in the abiraterone arm, most commonly hypertension and hypokalemia, although very few men stopped treatment due to these side effects.
Taken together, these studies show that giving abiraterone early in the treatment pathway can have striking survival benefits for men with advanced prostate cancer. Of note, these trials recruited before docetaxel + ADT became standard of care (following publication of an earlier arm of STAMPEDE) and we do not yet know how the benefits of docetaxel compare to abiraterone. Other questions that need to be answered include whether docetaxel and abiraterone can be administered concurrently or sequentially, and if there is a way to identify men who will respond better to one treatment versus the other. Until we have these answers, the choice of docetaxel or abiraterone will likely come down to a combination of patient and clinician choice, taking into account treatment duration, side-effect profiles, co-morbidities and cost-effectiveness.