Lack of accrual

Most of the local recurrences (LR) found after breast-conserving therapy are within or close to the tumor bed. This pattern of recurrence was confirmed by studies of breast conserving surgery without adjuvant irradiation and by the update of the NSABP B-06 trial. In the EORTC boost trial, however, 29% of all LR were found outside the area of the original tumor. Still, a recent review of Breast Conserving Therapy (BCT) trials showed that the site of local recurrences after BCT was mostly in the tumor bed, with less than 10% of LR elsewhere in the breast. This led to the concept of partial breast irradiation. With accelerated partial breast irradiation (APBI), a limited volume of breast tissue is irradiated, allowing for a higher dose per fraction compared to whole breast irradiation (WBI), which is favorable considering the low alpha/beta ratio, and thus higher sensitivity to high dose per fraction.

Patients will undergo a partial accelerated breast irradiation pre-or postoperative of 5 x 5.2 Gy

Inclusion Criteria:

• Female patients ≥ 51 years
• clinical stage tumor-1-2 (≤ 3 cm)
• cN0
• Grade I or grade II (biopsy)
• Histologically proven invasive ductal adenocarcinoma
• Unifocal lesions on mammogram and MRI (small satellite lesions adjacent to the tumor are accepted as long as it is suitable for local excision to be determined by the participating centre)
• World Health Organization performance status ≤ 2
• Life expectancy ≥ 5 years
• Written informed consent

Exclusion Criteria:

• Distant metastases
• Lobular invasive carcinomas
• Pure Ductal Carcinoma in situ (DCIS) without invasive tumor
• Grade III in biopsy
• Triple negative tumors
• HER2neu positive tumors
• Lymphvascular invasion in biopsy
• TNM pathologic stage N1-3
• pN+ (micro- or macrometastases)
• Multicentric / multifocal disease on mammogram or MRI
• Diffuse calcifications on mammogram (Birads 3, 4 or 5)
• Prior treatment for the protocol tumor (no surgery, no neoadjuvant chemotherapy or neoadjuvant hormonal therapy, no previous radiotherapy)
• Previous contralateral breast cancer
• Other neoplasms in the last 5 years with the exception of:
• Basal cell carcinoma of the skin
• Adequately treated carcinoma in situ of the cervix
• Planned oncoplastic resection with tissue displacement
• No social security affiliation/health insurance
• Participation in another clinical trial that interferes with the locoregional treatment of this protocol
• It is expected that dosimetric constraints cannot be met, ie, lung/heart constraints or if the ratio PTV/ipsilateral breast >30%

data from this clinical trial will be shared with the previous PAPBI clinical trial