MRI-guided Single Dose Preoperative Radiotherapy in Low-risk Breast Cancer

MRI-guided Single Dose Preoperative Radiotherapy in Low-risk Breast Cancer

This study aims to evaluate the pathologic response at 12 months after single dose preoperative partial breast irradiation in early stage breast cancer patients. Furthermore, the aim is to collect data on response monitoring. Patient-reported outcome measures and treatment-induced toxicity will be evaluated.

In this multi-center single arm interventional cohort study 70 patients will be treated with single dose preoperative partial breast irradiation (PBI). Breast conserving surgery will be performed 12 months following PBI to assess pathologic response. Response monitoring following PBI includes MRI (3T and 7T), liquid biopsies and biopsy of the irradiated tumor.

Results from this trial can change the current treatment of patients with early stage breast cancer. The single dose PBI can be of benefit for all patients who are suitable for postoperative PBI according to current guidelines. If pathologic complete response can be accurately predicted by (one of) the abovementioned response monitoring modalities, the need for surgery will become disputable. Moreover, in patients without expected pathologic complete response, the burden of radiotherapy can be minimized from 3-4.5 weeks of radiotherapy to a single dose of radiotherapy.

Inclusion Criteria:

• WHO performance scale ≤2.

• Females at least 50 years of age with unifocal cT1N0 breast cancer or females at least 70 years of age with unifocal cT1-2(maximum 3 cm)N0 breast cancer on mammography, ultrasound and MRI.

  • Patients with an indication for chemotherapy or immunotherapy according to Dutch National Oncoline Guidelines or own hospital protocols are not eligible. Patients with an indication for endocrine therapy are eligible.
  • Tumor size as assessed on MRI.

• On tumor biopsy:

  • Bloom-Richardson grade 1 or 2.
  • Non-lobular invasive histological type carcinoma.
  • LCIS or (non-extensive) DCIS is accepted.
  • ER positive tumor receptor.
  • HER2 negative tumor.

• Tumor-negative sentinel node.

• Adequate communication and understanding skills of the Dutch language.

Exclusion Criteria:

• Legal incapacity.
• BRCA1, BRCA2 or CHEK2 gene mutation.
• Previous history of breast cancer or DCIS.
• Other type of malignancy within 5 years before breast cancer diagnosis. Patients with adequately treated malignancy longer than 5 years before breast cancer diagnosis are eligible for inclusion. For adequately treated carcinoma in situ of the cervix or basal cell carcinoma of the skin no specific time span to breast cancer diagnosis is required for inclusion.
• Collagen synthesis disease.
• Signs of extensive DCIS component on histological biopsy or imaging.
• Invasive lobular carcinoma.
• MRI absolute contraindications as defined by the Department of Radiology.
• Nodal involvement with cytological or histological confirmation.
• Indication for treatment with (neo-)adjuvant chemotherapy.
• Non-feasible dosimetric RT plan.