Microwave Ablative (MWA) therapy, as a minimally invasive thermal therapy, has been attempted to treat breast cancer of small lesions . However, the optimal indications for MWA in the treatment of breast cancer is unknown. This prospective, open-label, single-arm phase II clinical study was conducted to evaluate the efficacy and safety of MWA in the treatment of early-stage unifocal invasive breast cancer, and to explore the immune activating effect.

Inclusion Criteria:

1. female patients aged 18-70 years;
2. patients with newly diagnosed invasive breast cancer confirmed by core needle biopsy;
3. the tumor smaller than 2cm in greatest diameter confirmed by US (ultrasonography), breast X-ray and breast MRI (contrast-enhanced magnetic resonance image ) were performed at the same time, and the difference of the largest diameter between breast US and MRI was less than 0.5 cm;
4. the single tumor without other suspicious lesions (BI-RADS (the Breast Imaging Recording and Data System) score ≥4) evaluated by breast US, X-ray and MRI;
5. the tumor without adhesion to chest wall, nipple or skin;
6. patients without distant metastasis;
7. Karnofsky performance status greater than 70%.

Exclusion Criteria:

1. multicentric or multifocal breast tumor;
2. the tumor located on nipple and areola area;
3. signs of extensive intraductal carcinoma on imaging examination (diffuse malignant calcification on breast X-ray or segmental distribution, non-mass enhancement, ductal or linear enhancement > 2.5 cm on MRI);
4. extensive intraductal component in invasive cancer (more than 50% of the tumor volume) confirmed by pathology;
5. invasive lobular carcinoma, metaplastic carcinoma or carcinoma with sclerosing adenosis;
6. patients who were pregnant or breastfeeding;
7. patients with evidence of coagulopathy, chronic liver diseases or renal failure;
8. patients with previous treatment including chemotherapy, targeted drug therapy, or local radiation therapy, etc;
9. patients with substance abuse, or mental or psychological disorders that may interfere with study compliance;
10. any condition that is unstable or likely to compromise the patient's safety and compliance;
11. patients enrolled in other clinical trials;
12. diseases or symptoms that other investigators consider unsuitable for participation.

Available from the corresponding author upon reasonable request