The OBSERB study aims to compare the oncologic outcomes of radiotherapy without sentinel lymph node biopsy versus sentinel lymph node biopsy for the management of breast cancer which showed the cN1 was conversed as ycN0 after neoadjuvant chemotherapy.
To verify whether, the radiotherapy without SLN can be applied, when the cN1 was conversed as ycN0 after neoadjuvant chemotherapy.
To verify whether, the additional treatment decision can be established based on only the biology of primary tumor without the pathologic information of axillary lymph nodes To verify whether, the patients' quality of life can be improved by a less invasive surgical procedure, when the cN1 was conversed as ycN0 after neoadjuvant chemotherapy.
