Level I-II Axillary Irradiation in Breast Cancer With Sentinel-Node Macro-metastases

PRIMARY OBJIECTIVE: To evaluate whether level I-II axillary irradiation is non-inferior to whole regional nodal irradiation in terms of disease-free survival in clinically node-negative breast cancer patients with 1-2 sentinel lymph node macro-metastases. SECONDARY OBJECTIVES: I. to estimate the difference of overall survival; II. to estimate the difference of ipsilateral regional recurrence; III. to estimate the difference of ipsilateral local regional recurrence; IV. to estimate the difference of distant recurrence; V. to estimate the difference of radiation related toxicities and quality of life. Outline: Patients are randomized in a 1:1 ratio to two treatment arms. Arm A (Level I-II axillary irradiation): Radiation is delivered to the breast after breast conserving surgery(BCS) or chest wall after mastectomy, level I-II axillary lymph nodes. Internal mammary nodes(IMN) is optional and it is recommended to irradiate IMN when the tumor is located in the medial or central quadrant. Arm B (Entire regional nodal irradiation): Radiation is delivered to the breast after BCS or chest wall after mastectomy, whole axillary lymph nodes (levels I-III) and supraclavicular lymph nodes. IMN is optional and it is recommended to irradiate IMN when the tumor is located in the medial or central quadrant.