Recruitment was very low.

This project aims to determine whether biopsy using radiofrequency is a procedure suitable for this patient selection. Findings from biopsy will be correlated with the conventional surgery ones. If the technique is validated to predict the presence or absence of residual tumor, breast surgery could be avoided in cases of absence of tumor.

Breast cancer is a set of at least 4 different diseases, currently known as intrinsic genomic subtypes. Two of them are the so-called HER2-enriched, characterized by the HER-2 oncogene amplification, and the basal-like, which correlates closely with some of the triple negative tumors (TNBC). These subtypes are very sensitive to the primary medical treatment (neoadjuvant or Presurgical). The use of modern medical treatments as initial treatment, can allow the complete disappearance of cancer in the breast and axilla (pathologic complete response, CPR) in 40% of patients with TNBC and around 60% of patients with HER2-positive tumors in stage II and III.

The need of local surgery in patients where the tumor disappeared completely (CPR) after primary medical treatment, is recently questioned, the improvement is not clear and radiotherapy could be sufficient to assure the locoregional disease control.

The use of conventional diagnostic techniques (MRI, ultrasound, mammography and PET) is not enough reliable to determine the pathological complete response, making difficult to adopt an attitude of surgical abstention. The existence of a minimally invasive technique that could reliably determine the absence of cancer after primary medical treatment surgery, could avoid the surgery in these cases.

Percutaneous biopsy guided by ultrasound radiofrequency is a technique that allows the complete resection of breast lesions up to 2 cm of diameter with minimal aggression to the mammary gland from the area of the initial tumor after the neoadjuvant treatment.

Several studies report the use of this technique in patients with breast cancer. Results show a good tolerability of the technique by the patients and suggest that it would not only reduce the need of the re-excision, but also reduce the rate of local recurrence due to radiation absence.

Biopsy using radiofrequency could be useful to confirm CPR in patients with triple-negative and HER2-positive tumors and several luminal B tumors and good response previously determined by conventional methods (MR in particular). Despite that, new prospective studies to analyse the reliability in patients selection with CPR and could avoid the traditional surgery are needed.

To confirm this hypothesis, a group of 100 treated patients with unicentered tumors in stages II or III and good response determined by MR after 6 cycles of treatment (less than 2 cm apparent residual injury) will be consecutively subjected to radiofrequency biopsy and the surgery previously established for each case (Tumorectomy or mastectomy). Before surgery, the sentinel node will be biopsied in order to define the surgical treatment on the axilla (none in case of negative sentinel node, axillary lymphadenectomy if positive).

The tumor samples obtained by percutaneous radiofrequency and mastectomy-Tumorectomy biopsy will be studied thoroughly to define the correlation between the two.

Inclusion Criteria:

• Informed consent Form signed
• Adequate Performance status (ECOG 0-1)
• Female patients with unifocal breast tumors (stages II-III, TN, HER2+ or Luminal B) very sensitive to neoadjuvant medical treatment (5 to 6 months in accordance with the current standard)
• Patients who submit clinical-radiologic greater response to the treatment administered (equal to or less than 1.5 cm in NMR residual tumor)

Exclusion Criteria:

• Ki67<14%
• Excisional biopsy Contraindications

Female patients with breast tumors sensitive to neoadjuvancy