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% > or = RTOG grade 1, p=0.004; 5 vs 15% > or = RTOG grade 2, p=0.01). There were no differences between groups in bladder function after treatment (53 vs 59% > or = grade 1, p=0.34; 20 vs 23% > or = 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.