Trial to Compare MRI-guided Precision Prone Irradiation (PPI) Versus CT-guided Breast Irradiation

Breast conserving surgery and adjuvant whole breast radiotherapy is a standard treatment option for most patients with early-stage invasive breast cancer. Recent technological advances in radiotherapy have enabled shorter treatment courses, smaller radiation fields, prone positioning, and fewer side effects associated with breast cancer treatment. To further improve target accuracy in breast radiation delivery, an emerging radiotherapy technology takes advantage of on-table MRI imaging and daily adaptive planning during the radiation delivery process. The objectives of the study are to compare side effects in patients treated under either of these treatment settings and to compare recurrence (if the cancer comes back) rates at a 2-year time point. Patients will have annual follow ups up to 10 years and recurrence rates will be measured at 5-year and at 10-year time points.