Hypofractionated Vs Conventional Fractionated Radiotherapy After Breast Conserving Surgery

Eligible patients after breast conserving surgery will be randomized 1:1 into hypofractionated radiotherapy (HF-RT) group or conventionally fractionated radiotherapy (CF-RT) group.

Patients in HF-RT group will receive 40 Gy/15 fractions irradiation to the whole breast with/without regional lymphnodes within 3 weeks and the tumor bed is boosted to 48 Gy/15 fractions simutaneously.

Patients in CF-RT group will receive 50 Gy/ 25 fractions irradiation to whole breast with/without regional lymphnodes within 5 weeks and the tumor bed is boosted to 60 Gy/30 fractions sequentially.

The primary endpoint is loco-regional recurrence. Other cancer related events and acute/late radiation morbidities will also be evaluated. The patients will be followed for 10 years.

It is hypothesized that hypofractionated radiotherapy is non inferior to conventional fractionated radiotherapy in terms of tumor loco-regional control for patients after breast conserving surgery.

Inclusion criteria

• Female
• Age18-70 years
• Imaging examination confirmed single lesion. if the tumor is multiple, it needs to be removed by single quadrantectomy
• Receive breast conserving surgery with negative margins
• Axillary lymph nodes treatment: Sentinel lymph node biopsy or level I/II axillary lymph node dissection. If the sentinel lymph node is negative, the axillary lymph node dissection can be omitted. If it is positive, level I/II axillary lymph node dissection with or more than 10 lymph nodes is needed.
• The tumor bed is labeled with clips and it can be drawn on the treatment planning system.
• 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 (in the 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 the skin
• 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 or follow up
• Unable or unwilling to sign informed consent