There are no randomised controlled trials to demonstrate a superiority of one treatment modality over the other in low-risk prostate cancer.
The key evidence supporting this protocol comes from: a meta-analysis by Viani et al. of 7 randomised controlled trials, including 2812 patients investigating dose escalation (greater than 70 Gy); the MRCRT01 and MD Anderson RCTs; and the RTOG 94.06 Michalski study.rrrrrr
Dose escalation (greater than 74 Gy) for patients with low-risk prostate cancer has previously shown limited benefit in this setting.
Viani et al. found a significant reduction in the incidence of biochemical failure in patients with low, intermediate and high-risk localised prostate cancer; 24.8% with high dose radiation therapy versus 34.6% with conventional dose radiation therapy (p <0.0001).r On subgroup analysis, all subgroups showed a linear correlation between total dose of radiation therapy and biochemical failure. The subgroup analyses of 4 RCTs and 602 low-risk patients, showed high dose radiation therapy reduces the relative risk of biochemical failure by approximately 50%, however, no difference in mortality rate and prostate cancer-specific mortality rates between high dose and conventional dose radiation therapy was demonstrated.r
Figure 2. Meta-analysis regarding biochemical failure for all subgroups
© Int J Radiat Oncol Biol Phys 2009r
The MDACC phase III RCT compared 70 Gy to 78 Gy EBRT. At 8 years post-radiation, patients with low-risk disease in the 78 Gy group had a freedom from failure (clinical and/or biochemical) of 88% compared to the 70 Gy group who had a freedom from failure rate of 63% (p = 0.042). No dose related effect on freedom from failure was found for favourable patients with a pre-treatment PSA <10 ng/ml.r
© Int J Radiat Oncol Biol Phys 2008r
To date, no randomised trial has documented a survival benefit attributable to higher radiation doses. The RTOG 94.06 phase II trial (1084 patients randomised across 5 dose levels) also confirmed dose escalation yields favourable outcomes for localised prostate cancer.r
© Int J Radiat Oncol Biol Phys 2012r
Hypofractionation is recommended for prostate only radiation therapy. Long-term outcomes and toxicity are comparable to conventional fractionation.rr Evidence supporting moderate hypofractionation for low-risk prostate cancer is not discussed within this protocol, but can be found in the evidence and efficacy sections of ID 3370 Prostate adenocarcinoma definitive EBRT hypofractionation.