Abstract
The relative effects of radiation dose escalation (RDE) and androgen suppression (AS) duration on local prostatic progression (LP) remain unclear.
We addressed this in the TROG 03.04 RADAR trial by incorporating a RDE programme by stratification at randomisation. Men were allocated 6 or 18months AS±18months zoledronate (Z). The main endpoint was a composite of clinically diagnosed LP or PSA progression with a PSA doubling time ⩾6months. Fine and Gray competing risk modelling with adjustment for site clustering produced cumulative incidence estimates at 6.5years for each RDE group.
Composite LP declined coherently in the 66, 70 and 74Gy external beam dosing groups and was lowest in the high dose rate brachytherapy boost (HDRB) group. At 6.5years, adjusted cumulative incidences were 22%, 15%, 13% and 7% respectively. Compared to 6months AS, 18months AS also significantly reduced LP (p<0.001). Post-radiation urethral strictures were documented in 45 subjects and increased incrementally in the dosing groups. Crude incidences were 0.8%, 0.9%, 3.8% and 12.7% respectively.
RDE and increasing AS independently reduce LP and increase urethral strictures. The risks and benefits to the individual must be balanced when selecting radiation dose and AS duration.