Comparison of radiation side-effects of conformal and conventional radiotherapy in prostate cancer: a randomised trial

Background Radical radiotherapy is commonly used to treat localised prostate cancer. Late chronic side-effects limit the dose that can be given, and may be linked to the volume of normal tissues irradiated. Conformal radiotherapy allows a smaller amount of rectum and bladder to be treated, by shaping the high-dose volume to the prostate. We assessed the ability of this new technology to lessen the risk of radiation-related effects in a randomised controlled trial of conformal versus conventional radiotherapy. Methods We recruited men with prostate cancer for treatment with a standard dose of 64 Gy in daily 2 Gy fractions. The men were randomly assigned conformal or conventional radiotherapy treatment. The primary endpoint was the development of late radiation complications (>3 months after treatment) measured with the Radiation Therapy and Oncology Group (RTOG) score. Indicators of disease (cancer) control were also recorded. Findings In the 225 men treated, significantly fewer men developed radiation-induced proctitis and bleeding in the conformal group than in the conventional group (37 vs 56% greater than or equal to RTOG grade 1, p = 0.004; 5 vs 15% greater than or equal to RTOG grade 2, p = 0.01). There were no differences between groups in bladder function after treatment (53 vs 59% greater than or equal to grade 1, p = 0.34; 20 vs 23% greater than or equal to grade 2, p = 0.61). After median follow-up of 3.6 years there was no significant difference between groups in local tumour control (conformal 78% [95% CI 66-86], conventional 83% [69-90]). Interpretation Conformal techniques significantly lowered the risk of late radiation-induced proctitis after radiotherapy for prostate cancer. Widespread introduction of these radiotherapy treatment methods is appropriate. Our results are the basis for dose-escalation studies to improve local tumour control.