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 the meta-analysis by Viani et alr of 7 randomised controlled trials including 2812 patients investigating dose escalation (>70Gy), and the Dutch,r MRCRT01 and MD Anderson RCTsrrr and Michalskir study.
Dose escalation (>74Gy) for patients with low risk prostate cancer has previously shown limited benefit in this setting.
Viani et alr 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 RT (HDRT) vs 34.6% with conventional dose RT (CDRT) (p < 0.0001) (see graph below). On subgroup analysis, all subgroups showed a linear correlation between total dose of radiotherapy and biochemical failure. Analyses of 4 RCTs and 602 low risk patients showed that HDRT reduces the relative risk of biochemical failure by 50%, however, no difference in mortality rate and specific prostate cancer mortality rates between HDRT and CDRT was demonstrated.
© Int J Radiat Oncol Biol Physics. Viani et al, 2009r
The MDACC phase III RCT compared 70Gy or 78Gy EBRT. At 8 years post radiation, patients with low risk disease in the 78 Gy group had a freedom from failure (FFF - clinical and/or biochemical) of 88% vs, 70Gy group who had an FFF of 63% (p = 0.042). No dose related effect on FFF was found for favourable patients with a pre-treatment PSA < 10ng/mL.r
© Int J Radiat Oncol Biol Phys 2008 Kubanr
To date no randomised trial has documented a survival benefit attributable to higher radiation doses. The results from the RTOG 9406 phase II trial reported by Michalski et al,r also confirmed dose escalation yields favourable outcomes for localised prostate cancer. 1084 patients were randomised across 5 dose levels.
© Int J Radiat Oncol Biol Phys 2012 Michalskir
Hypofractionation is currently under investigation.rr Early data from these studies is encouraging offering equivalent toxicity however long term biochemical control rates are awaited.