Due to differences in the control arms of these two trials complementary findings were obtained that strengthened the overall take-home message. The RADAR trial used 6 months of androgen suppression and radiotherapy as its control because its predecessor the TROG 9601 trial found that 6 months androgen suppression reduced metastases and prostate cancer deaths by 50% when compared radiotherapy alone. The French Canadian trial lead by Nabid et al used 36 months of androgen suppression and radiotherapy as its control because two successful trials designed by Bolla et al were widely considered to be the standard of care for men with high risk, locally advanced prostate cancers.
Except for a small early increase in adverse patient-reported outcomes, the results of the RADAR trial indicated that 18 months of androgen suppression and radiotherapy was clearly more effective than 6 months of androgen suppression and the same radiotherapy as its control. Effect sizes for a wide range of outcomes, including the primary endpoint prostate cancer-specific mortality were in the range 30-40%. Results from the French Canadian trial lead by Nabid et al were more surprising because 36 months of androgen suppression did not appear to reduce prostate specific or all-cause mortality outcomes when compared with 18 months. However less surprisingly adverse patient-reported outcomes were significantly greater in participants who received 36 months of androgen suppression.
Taken together the RADAR and French Canadian trials indicated that 18 months of androgen suppression would likely become a new standard of care for men with locally advanced, high-risk prostate cancer that could be supplemented by newly evolving pharmaceuticals over the next 10-15 years.
The electronic supplement the RADAR trials 10 year main endpoints report in The Lancet Oncology includes many additional findings that many readers will find interesting. Readers are also likely to be interested in two substudies of the RADAR trial that is likely to be reported in 3-4 months time. The first seeks to establish an answer to the much-debated topic as to whether radiation dose escalation and/or 12 additional of androgen suppression is more effective. The second substudy seeks to explain why perineural prostate cancer invasion prior to treatment adversely influences a wide range of outcomes.
Written by: Conjoint Professor Jim Denham, School of Medicine and Public Health, University of Newcastle, Newcastle, New South Wales, Australia
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