The PROSPECTIVE trial aims to find out if using the results of Magnetic Resonance Imaging (MRI) for early breast cancer can select people to not have radiotherapy and still have a low chance of the cancer coming back after surgery.
The main question it aims to answer is:
\* Will cancer come back in the same breast as the original cancer in patients who have surgery for their breast cancer, but who don't have radiotherapy afterwards because the results of an MRI before surgery showed favourable characteristics for not having radiotherapy.
Has provided written, informed consent to participate in the study.
Female participants ≥ 50 years old with histologically* confirmed ER-positive and/or HER2-positive invasive breast cancer.
Has a life expectancy of at least 10 years and suitable for prolonged follow up for 10 years.
Breast imaging indicating unifocal, unilateral breast cancer must have been performed before pre-registration.
Triple negative breast cancer (ER-negative and PR-negative and HER2-negative) where ER and PR positivity is defined as ≥ 10% staining on IHC.
Previous invasive breast cancer and/or DCIS in either breast.
Prior RT to the breast or chest.
Participants who plan to have a mastectomy for the index cancer.