Single-Fraction Very Accelerated Partial Breast Irradiation (sfVAPBI)

Accelerated Partial Breast Irradiation (APBI) has demonstrated the non-inferiority compared to external beam radiotherapy (EBRT) in the conserving-treatment of early breast carcinoma by using high-dose-rate (HDR) multicatheter interstitial brachytherapy (MIBT). The standard treatment regimen is 7-8 sessions with two treatments per day, for a total treatment time of 4-5 days. Based on 5-year results of the Groupe Européen de Curiethérapie European SocieTy for Radiotherapy & Oncology (GEC-ESTRO) Very Accelerated Partial Breast Irradiation (VAPBI) phase I-II trial, in low-risk cases, 3-4 fractions delivered in 2 days reduced the overall treatment time with low rate of side effects and excellent oncological outcome.

Retrospective and prospective studies with a single fraction HDR MIBT-based VAPBI suggest that by further increasing the dose delivered in one fraction, the total treatment time can be reduced to a single session safely.

A phase II multicenter trial is proposed to confirm this hypothesis.

Inclusion criteria

• Stage 0 & I & II (< 3 cm) breast carcinoma
• Lesions of < 3 cm diameter
• Invasive carcinoma of any subtype and grade or ductal carcinoma in situ (DCIS)
• Nodal status: node-negative (pN0) or micro-metastatic (pN1mi) (patients with pN1mi status can be treated, but due to the limited clinical evidence, individual decision is needed)
• M0: Absence of distant metastasis
• Clear resection margins by National Surgical Adjuvant Breast and Bowel Project (NSABP) definition (no tumor on ink)
• Unifocal (multifocality limited within 2 cm) and unicentric breast cancer
• Age> 40 years
• Luminal A or B tumors
• Time interval from surgery preferably less than 12 weeks and no longer than 20 weeks, and from adjuvant chemotherapy less than 4 weeks
• Human Epidermal growth factor Receptor 2 positive (HER2+) patients receiving postoperative anti-HER2 systemic therapy
• Specific signed consent form prior to randomization

Exclusion criteria

• Stage III-IV breast cancer
• Surgical margins that cannot be microscopically assessed
• Extensive intraductal component (EIC+)
• Extensive lymphovascular invasion (LVI+) (focal is allowed)
• Triple negative breast cancer
• BReast CAncer gene (BRCA) 1-2 mutation
• Human Epidermal growth factor Receptor 2 positive (HER2+) patients not receiving postoperative anti-HER2 systemic therapy
• Neoadjuvant systemic therapy
• Paget's disease or pathological skin involvement
• Synchronous or previous breast cancer.
• Pregnant or lactating women