Hypofractionated Vs Conventional Fractionated Radiotherapy After Breast Conserving Surgery

Inclusion Criteria:

• Female

• Age18-70 years

• Imaging examination confirmed single lesion. if the tumor is multiple, it needs to beremoved by single quadrantectomy

• Receive breast conserving surgery with negative margins

• Axillary lymph nodes treatment: Sentinel lymph node biopsy or level I/II axillarylymph node dissection. If the sentinel lymph node is negative, the axillary lymph nodedissection can be omitted. If it is positive, level I/II axillary lymph nodedissection with or more than 10 lymph nodes is needed.

• The tumor bed is labeled with clips and it can be drawn on the treatment planningsystem.

• Pathologically confirmed invasive breast cancer

• Pathologically stage is T1-3N0-3M0

• Immunohistochemical examination is conducted to determine the status of ER, PR, HER2,Ki67 after surgery

• No distant metastases

• No supraclavicular or internal mammary nodes metastases

• No neoadjuvant chemotherapy

• Fit for postoperative radiotherapy. No contraindications to radiotherapy

• KPS≥80

• Signed informed consent

Exclusion Criteria:

• T4 or M1 breast cancer

• Supraclavicular or internal mammary nodes metastases

• Pathologically confirmed DCIS only without an invasive component

• Bilateral breast cancer or historically confirmed contralateral invasive breast cancer

• Treated with neoadjuvant chemotherapy or neoadjuvant endocrine therapy

• Multiple lesions can not be removed by single quadrantectomy

• Suspicious unresected and microcalcification, densities, or palpable abnormalities (inthe ipsilateral or contralateral breast)

• KPS ≤ 70

• Patients with severe non-malignant comorbidity in cardiovascular or respiration system

• Concurrent or previous malignancy excluding basal or squamous cell carcinoma of theskin

• Previous radiotherapy to the chest wall or regional lymph node areas

• Patients with medical contraindication for radiotherapy: systemic lupus erythematosus,cirrhosis

• Pregnant or lactating

• Conditions indicating that the patient cannot go through the radiation therapy orfollow up

• Unable or unwilling to sign informed consent