A Phase III Study of Adjuvant Radiation Therapy in Early Breast Cancer Comparing the Use of Breast Intensity Modulated Radiation Therapy (IMRT) to Conventional Wedge Technique

1. Description of the Problem:

The majority of breast cancer patients are treated with breast-conserving surgery followed by radiotherapy, giving loco-regional control rates similar to mastectomy. Currently, the "standard" breast radiotherapy technique includes treatment of the entire breast with a tangential opposed pair of photon beams. The standard technique leads to significant acute skin toxicity, ranging from breast erythema to moist desquamation, in approximately 40% of patients. This toxicity may lead to interruptions in treatment delivery; may increase the risk of developing late skin toxicity including telangiectasia, skin fibrosis and chronic breast pain; and may also be associated with a significant decrease in health-related quality of life (HRQOL). Published data from dosimetric studies suggest that dose variations in excess of 10% within the breast may be the most important predictor of acute radiation-induced skin toxicity (RR = 9.7), and that dose toxicity occurs more frequently in the inframamary fold. A study performed at TSRCC shows that intensity modulated radiotherapy (IMRT) allows for significant improvements in dose homogeneity within the breast compared to standard breast radiotherapy techniques. Furthermore, the hot spot over 10% seen in the inframamary fold for patient with large breast volume is removed. 2. Objectives:

• To determine if the occurence of acute skin toxicity in women receiving adjuvant breast radiation with IMRT is less frequent compared to women treated with conventional technique.
• To determine if the HRQOL scores, and specifically breast module subscale scores, in women receiving adjuvant breast radiation with IMRT is better than HRQOL scores in women receiving conventional technique.
• To perform a comparison of costs in the delivery of breast radiotherapy using IMRT to conventional technique.
• To determine if an increased acute skin toxicity translates into an increased late skin toxicity.

3. Hypothesis:

We hypothesize that women receiving adjuvant breast radiation with IMRT will have significantly less acute skin toxicity and improved HRQOL compared to women treated with conventional techniques. We also hypothesize that there would not be increased cost related to IMRT compared to conventional technique.

Research plan: A Phase III randomised controled trial is planned, with blocked stratification on breast size and boost delivery. Eligible women include those who have been referred to TSRCC following breast-conserving surgery. They will be randomized to receive either a conventional technique treatment, either breast IMRT. Acute skin toxicity will be assessed weekly during radiotherapy and up to one month following completion of radiotherapy using the previously validated RTOG acute skin toxicity scale. The occurence, duration and intensity of acute skin toxicity will be compared. HRQOL will be assessed during and after irradiation, using validated EORTC instruments (EORTC QLQ-C30 and QLQ-BR23). 340 patients will be accrued in order to detect a 15% reduction in the ocurence of acute skin toxicity with IMRT using an a=0.05, b=0.80.