Patient recruitment was not feasible.

This study evaluates the efficacy of MR-HIFU ablation of breast cancer. Ten patients with early-stage breast cancer with a maximum diameter of 3 cm will undergo MR-HIFU ablation, followed by MRI and surgical resection to evaluate treatment effect. The main purpose of the study is to demonstrate the feasibility of total tumor ablation with MR-HIFU. The secondary objective is safety assessment.

Inclusion Criteria:

• Women, aged 18 years and older.
• Able to give informed consent herself.
• World Health Organization (WHO) performance score ≤ 2.
• Biopsy proven cT1-2 N0-2 MX invasive breast cancer with a size of ≤ 3.0 cm.
• Histological type of tumor: invasive ductal carcinoma (IDC), not otherwise specified (NOS) or no special type (NST).
• The target breast fits in the cup of the dedicated MR-HIFU breast system.
• Patient weight is limited to ≤ 90 kg, because of restrictions to the HIFU table top.

Additional inclusion criteria based on DCE-MRI findings:

• The distance of the tumor, including a 5 mm margin around the tumor, from the skin, nipple and pectoral wall is at least 1.0 cm measured on MRI.
• The tumor is located within the reach of the HIFU beam produced by the transducers in the HIFU breast system.

Exclusion Criteria:

• Prior treatment with: neo-adjuvant systemic therapy in the past 3 months or radiotherapy or thermal therapy or surgery of any kind in the targeted breast.
• Contraindications to MR imaging according to the hospital guidelines (e.g. pacemaker in situ, severe claustrophobia, big metal implants, body size incompatible with MR bore).
• Contraindications to administration of gadolinium-based contrast agent, including: prior allergic reaction to a gadolinium-based contrast agent, kidney disease (e.g. nephrogenic systemic fibrosis, nephrogenic fibrosing dermopathy) and/or renal failure (GFR < 30 ml/min/1,73m2).
• Contra-indications for procedural sedation analgesia with Propofol and Esketamine or Propofol and Remifentanil.
• Extensive intraductal components in the lesion determined by biopsy.
• Scar tissue or surgical clips in the HIFU beam path.
• Inability to lie in prone position.
• Pregnancy or lactation.
• Communication barrier with patient.

The following groups of patients will be excluded because the risk of adjuvant over- or undertreatment due to performing the Bloom and Richardson (B&R) grading on the tumor biopsy is considered to high:

• N0, Her2neu negative, <35 years, ≤1cm (T1a/b) with B&R grade 1 or 2 on biopsy.
• N0 Her2neu negative, ER/PR negative (triple negative), 35-70yr, 1.1-2cm (T1c) with B&R grade 1 or 2 on biopsy.
• N0, Her2neu negative, ER/PR positive > 50%, ductal carcinoma, 60-70yr, 1.1-2cm (T1c), with B&R grade 3 on biopsy and if the MammaPrint is not reimbursed by health insurance also for grade 1 on biopsy.
• N0, Her2neu negative, ER/PR positive, ductal carcinoma, 35-60yr, 1.1-2cm (T1c) with B&R grade 1 on biopsy.
• N0, Her2neu negative, ER/PR positive, but ≤50%, ductal carcinoma, 60-70yr, 1.1-2cm (T1c) with B&R grade 1.

The following group of patients will be excluded based on the results of the MammaPrint:

• Only if the MammaPrint is reimbursed by health insurance: N0, Her2neu negative, ER/PR positive, > 50% ductal carcinoma, 60-70yr, 1.1-2cm (T1c), with B&R grade 1 and MammaPrint high risk.