A randomised controlled trial of forward-planned radiotherapy (IMRT) for early breast cancer: Baseline characteristics and dosimetry results

Background and purpose

This large trial was designed to investigate whether correction of dose inhomogeneities using intensity-modulated radiotherapy (IMRT) reduces late toxicity and improves quality of life in patients with early breast cancer. This paper reports baseline characteristics of trial participants and dosimetry results.

Materials and methods

Standard tangential plans of 1145 trials were analysed. Patients with inhomogeneous plans, defined by ICRU recommendations, were randomised to forward-planned IMRT or standard radiotherapy.

Results

Twenty-nine percentage of patients had adequate dosimetry with standard 2D radiotherapy. In the randomised patients, the decreases in mean volumes receiving greater than 107% (Vol > 107) and less than 95% (Vol < 95) of the prescribed dose in the IMRT compared with the control group were 34.0 cm³ (95% CI 26.4-41.6; P < 0.0001) and 48.1 cm³ (95% CI 34.4-61.9; P < 0.0001), respectively. In this study, 90% of patients who had a breast separation greater ?21 cm had Vol > 107 > 2 cm³ on standard radiotherapy plans.

Conclusion

This large trial, in which patients with all breast sizes were eligible, confirmed that breast dosimetry can be significantly improved with a simple method of forward-planned IMRT and has little impact on radiotherapy resources. It is shown that patients with larger breasts are more likely to have dose inhomogeneities and breast separation gives some indication of this likelihood. Photographic assessment of patients at 2 years after radiotherapy, as the next part of this randomised controlled trial, will show whether these results for IMRT translate into improved cosmetic outcome in patients with early breast cancer. This would provide impetus for the widespread adoption of 3D planning and IMRT.