Super Hypofractionated Irradiation for Whole Breast Treatment

Super Hypofractionated Irradiation for Whole Breast Treatment: a Prospective, Single-arm Trial

The purpose of this trial is to investigate the safety and efficacy of super hypofractionated whole breast irradiation (SHF-WBI) in breast cancer patients treated with breast conserving surgery. Eligible breast cancer patients will be followed for at least 5 years to evaluate the acute and late radiation-induced toxicities, locoregional recurrence, distant metastasis, death, contralateral breast cancer and quality of life.

Eligible breast cancer patients will receive SHF-WBI of 5.2 Gy in 5 fractions to ipsilateral whole breast within one week and a sequential tumor bed boost of 5.2 Gy in 2 fractions at the discretion of the radiation oncologist. All patients are treated with intensity modulated radiation therapy (IMRT) technique. The primary endpoint is ≥2 grade any acute radiation induced toxicity event. Patients will be followed for at least 5 years to evaluate the acute and late radiation-induced toxicity, locoregional recurrence, distant metastasis, death and quality of life.

Calculation of the required number of cases based on an alpha of 0.05 and a power of 80% with a maximal tolerable toxicity difference of 10% during and within 6 months after SHF-WBI comparing to hypofractionated whole breast irradiation(40-42.5Gy/15-16Fx) and lost rate of follow up of 10%. In total 217 patients are needed to be recruited.

Inclusion Criteria:

• Written informed consent
• Aged ≥18 years old
• breast conservation surgery
• unilateral histologically confirmed invasive breast carcinoma or Ductal Carcinoma In Situ (DCIS)
• For patients with invasive breast cancer，negative axillary lymph nodes or micrometastasis only
• Karnofsky Performance Status ≥80, and Life expectancy of >5 years
• Histologically negative surgical margin for invasive breast carcinoma or a minimum negative margin width of ≥ 3mm for DCIS
• Surgery wound healed without infection
• ER (estrogen-receptor), PR (progesterone-receptor), HER2 (human epidermal growth factor receptor 2) and Ki67 testing can be performed on the primary breast tumor
• Female patients of child-producing potential must agree to use effective contraception for up to 1 month before study treatment and the duration of study participation

Exclusion Criteria:

• Histological involvement of supraclavicular lymph node
• Histologically or radiologically confirmed involvement of ipsilateral internal mammary lymph nodes
• Pregnant or lactating women
• Severe non-neoplastic medical comorbidities
• Diagnosis of non-breast malignancy within 5 years preceding enrollment (excluding lobular carcinoma in situ, basal cell carcinoma of the skin, carcinoma in situ of skin and carcinoma in situ of the cervix, Pulmonary adenocarcinoma in situ，which are permitted).
• simultaneous contralateral breast cancer
• Previous radiotherapy to the neck, chest and/or ipsilateral axillary region
• Active collagen vascular disease
• Definitive histological or radiologic evidence of distant metastatic disease
• Evidence of T4 disease