A Randomised Controlled Trial of Forward-Planned Intensity Modulated Radiotherapy (IMRT) for Early Breast Cancer: Interim Results at 2 Years Follow-Up.

Abstract

Abstract Background: This large single centre trial was designed to investigate whether correction of dose inhomogeneities using IMRT reduces late toxicity and improves quality of life in patients with early breast cancer. We report interim results at 2 years follow-up.Materials and Methods: Standard tangential breast radiotherapy plans of 1145 trial patients were assessed for dose inhomogeneity as defined by ICRU recommendations. Patients with inhomogeneous plans were randomised to either IMRT or standard radiotherapy. Patients with homogenous plans were treated with standard radiotherapy, but were followed up within the trial as per randomised patients. The primary endpoint of the trial was photographic assessment of breast shrinkage. Secondary endpoints included photographic assessment of final cosmesis, clinical assessment of toxicity, and patient-reported symptoms and quality of life. All endpoints were scored using validated assessment methods. Data were collected on potential confounding factors which included: age at randomisation, smoking history, body mass index, co-morbidity such as diabetes mellitus, cardiovascular and peripheral vascular disease, use of hormones and/or chemotherapy, treated breast volume, and presence or absence of breast boost.Results: 330/1145 (29%) of patients had adequate dosimetry with standard 2D radiotherapy and were not randomised. In the 815 randomised patients, dosimetry was significantly improved in the interventional (IMRT) arm compared to the control. Currently, data from 632 randoimsed patients who have reached 2 years of follow up have been analysed. This interim analysis demonstrates that the incidence of telangiectasia in the control arm was significantly greater than in the interventional group (P = 0.024). Pre-radiotherapy surgical cosmesis significantly affected photographic assessment of final cosmesis, and clinical assessment of breast shrinkage and induration (P < 0.0001). In randomised patients who had good surgical cosmesis, there was a significant difference improvement in final cosmesis with the use of IMRT (P = 0.038). The quality of life data has not been analysed at this stage.Discussion: This trial shows that the use of forward-planned IMRT can significantly improve dose homogeneity, and suggests that this translates into improvements in late toxicity at only 2 years from completion of radiotherapy. Surgical cosmesis appears to be a very important determinant of overall final cosmesis after 2 years of follow-up, and may mask any beneficial effects of IMRT at this early stage. It is highly likely that these trial patients will have not expressed their final level of toxicity at 2 years post-radiotherapy, and re-analysis is planned at 5 years from completion of radiotherapy. Citation Information: Cancer Res 2009;69(24 Suppl):Abstract nr 71.