The Absolute Effect / Prostate Cancer / Radiation
With curative-intent radiotherapy for locally advanced prostate cancer, does extending androgen suppression from 6 to 18 months improve long-term prostate-cancer outcomes?
1,071 men with locally advanced prostate cancer; randomized 2×2 factorial design comparing 6 versus 18 months of androgen suppression, with or without zoledronic acid.
Six months: leuprorelin 22.5 mg every 3 months. Eighteen months: the same initial 6 months plus 12 additional months. Radiotherapy was 66, 70 or 74 Gy, or 46 Gy plus HDR brachytherapy 19.5 Gy in 6.5-Gy fractions.
At 10 years, adjusted prostate-cancer-specific mortality was 13.3% with 6 months vs 9.7% with 18 months: absolute reduction 3.7 percentage points (95% CI 0.3–7.1), sHR 0.70 (95% CI 0.50–0.98), p=0.035. Approximate NNT for prostate-cancer-specific death by 10 years = 27, with uncertainty reflected by the CI.
Ten-year distant progression was also reduced with longer androgen suppression (sHR about 0.70); there was no evidence that the effect depended on radiotherapy dose.
Zoledronic acid did not improve prostate-cancer-specific mortality: 11.2% versus 11.7%, absolute difference −0.5 percentage points; sHR 0.95, p=0.78.
RADAR addresses ADT duration, not whether pelvic RT should be given. In this RT-treated locally advanced population, extending ADT to 18 months produced a modest absolute reduction in prostate-cancer-specific mortality.
Lancet Oncology 10-year report · 10-year distant-progression analysis.
TROG 03.04 RADAR supports 18 months rather than six months of androgen deprivation with radiotherapy for selected locally advanced/high-risk prostate cancer, improving prostate-cancer outcomes. Contemporary duration should be individualized by risk, RT regimen, comorbidity, cardiovascular/metabolic/bone health and patient preference; the trial does not establish that every patient needs the same ADT duration.