The purpose of this study is to evaluate acute local toxicity of IORT at the dose of 20 Gy for the replacement of boost-external beam radiotherapy in Korean women who are candidates for breast-conserving treatment.

Local toxicity checklist

• Hematoma needing surgical evacuation
• Seroma needing more than three aspirations
• Skin breakdown or delayed wound healing
• Any complication needing surgical intervention
• Radiation Therapy Oncology Group (RTOG version 2.0) toxicity grade 3 or 4 for dermatitis, telangiectasia, pain in irradiated field, or other.
• Any complication of RTOG toxicity grade more than 2

Inclusion Criteria:

• Histologically confirmed and newly diagnosed non-metastatic operable primary breast cancer
• Primary tumor <5cm, measured by ultrasonography - N0-3 (any N if resectable) and no evidence of distant metastasis (M) (isolated supraclavicular node involvement allowed)
• Age ≥18-years women with good performance status (ECOG 0-1)
• No breast operation is allowed except diagnostic biopsy
• Women with ductal carcinoma in situ diagnosed by preoperative biopsy are allowed

Exclusion Criteria:

• Pregnancy or unwillingness to use a reliable contraceptive method in women of child-bearing potential.

• Patients who received prior chemotherapy or radiotherapy for breast cancer

• Patients who have history of cancer other than in situ uterine cervix cancer or non-melanoma skin cancer

• The depth of tumor from skin measured by ultrasonography is less than 1cm.

• Contraindications to breast conservative surgery

  • Multicentric breast cancer (tumors in more than one quadrant)
  • Diffuse malignant appearing microcalcification
  • Prior therapeutic radiation to the breast region
  • Small breast, which is not possible to achieve clear margins in relation to a cosmetically acceptable result
  • History of collagen vascular disease, such as active scleroderma and active lupus

• Postoperative exclusion

  • Patients who require re-excision due to positive resection margin
  • The depth of cavity from skin after lumpectomy is less than 0.5cm