WILL MULTIFUNCTIONAL MAGNETIC RESONANCE TECHNIQUES, DETAILED HISTOPATHOLOGICAL ANALYSIS AND PRONE TREATMENT POSITION IMPROVE ACCURACY OF TARGET VOLUME LOCALISATION & DEFINITION AND REDUCE EXPOSURE OF NORMAL TISSUES IN BREAST RADIOTHERAPY?

OBJECTIVES:

• To improve precision of tumor bed localization and definition of clinical target volume, and to reduce normal tissue irradiation in women undergoing partial breast or breast boost radiotherapy.
• To test whether post-operative MRI improves the precision of tumor bed delineation after wide-local excision in comparison with the current standard CT scan/clip method.
• To determine the impact of tumor position within the excision specimen upon the localization of clinical target volume in relation to the tumor bed.
• To compare theoretical non-target tissue exposure from partial breast irradiation planned in the supine and prone (face-down) positions.

OUTLINE: Patients undergo planned breast-conservation surgery and placement of titanium clips to the four radial, the deep, and superficial margins of the excision cavity (for localization of tumor bed).

Within 2 weeks after surgery, patients undergo supine radiotherapy-planning CT scan as standard analysis. Patients then undergo a radiotherapy-planning CT scan in the prone position. Patients complete a linear analogue questionnaire after both scans designed to assess patient comfort and anxiety in each position. Patients then undergo multifunctional MRI (including dynamic contrast-enhancement MRI and diffusion-weighted MRI) of the ipsilateral breast in the prone position (≥ 3 weeks after surgery). If suspicious lesions ≥ 5 mm are found on MRI, patients are referred for a second-look ultrasound with biopsy (if lesion visible on ultrasound); where suspicious lesions are seen only on MRI, patients undergo MRI-guided biopsy. Lesions < 5 mm are included in the whole-breast radiotherapy treatment.