Researchers from SWOG Cancer Research Network have significantly extended median survival for patients with hormone-sensitive metastatic prostate cancer. This result comes from a large randomized clinical trial aimed at testing a new treatment for these patients. The findings of the research were published in the ‘Journal of Clinical Oncology.
It tested the efficiency of the drug orteronel in these patients, pairing it with androgen deprivation therapy on the investigational arm and comparing that combination to androgen deprivation therapy plus bicalutamide. Although the study missed the primary endpoint of a 33 percent improvement in overall survival (OS), it also showed an unprecedented median OS of 70 months in the control arm, the highest ever reported for these patients on a non-intensified androgen deprivation therapy arm.
This OS is a 24-month improvement over results reported in 2013 from the SWOG-9346 trial, which enrolled a nearly identical proportion of patients with extensive disease. The researchers conclude that the primary reason for this extended survival compared to previous studies is the life-prolonging additional treatments patients received after they completed the S1216 trial.
Some 77 percent of control arm patients whose cancer progressed went on to get additional life-prolonging treatment after finishing the trial therapy, compared to 61 percent in the orteronel arm. “We are seeing the benefit of the advancements made in advanced prostate cancer therapy in the last decade, resulting in unprecedented improvements in survival of men with advanced prostate cancer in general, which is great news for our patients,” said study lead author Neeraj Agarwal, MD, a SWOG investigator with the Huntsman Cancer Institute at the University of Utah.
In setting the measure of success for the trial as an improvement in OS of at least 33 percent, the S1216 study team had worked from the assumption that the median control arm OS would be 54 months, a figure that built on the SWOG-9346 results and added time to account for the anticipated impact of new drugs then being reviewed for approval. Because the actual median control arm OS exceeded this assumption by 16 months, the results did not meet the threshold for S1216 to be considered a positive trial.
Men on the orteronel arm also had significantly improved median progression-free survival (47.6 months versus 23.0 months) and prostate-specific antigen (PSA) response rates measured at seven months after the start of treatment (complete-, partial-, and no-response rates of 58, 22, and 19 percent versus 44, 31, and 25 percent); these were secondary endpoints in the trial.