How many treatments of radiation therapy are required for Ductal Carcinoma In Situ (DCIS) lumpectomy?

Radiation Therapy Requirements for DCIS Lumpectomy

Standard radiation therapy for DCIS after lumpectomy requires 25 treatments delivered as whole-breast radiation therapy at a dose of 4,500 to 5,000 cGy (180-200 cGy per fraction), with each field treated daily Monday through Friday. 1

Standard Radiation Protocol

• Radiation therapy typically begins 2-4 weeks after uncomplicated breast-conserving surgery, once adequate healing has occurred 1
• Treatment is delivered using opposed tangential fields to encompass the tumor bed, surrounding tissue, and most of the ipsilateral breast 1
• Each treatment field should be administered daily (Monday through Friday) for a total of 25 fractions 1
• Bolus should not be used during treatment 1

Dosage Details

• Standard whole-breast radiation therapy dose is 4,500 to 5,000 cGy delivered at 180 to 200 cGy per fraction 1
• Higher energy photons (≥10 MV) may be indicated for very large-breasted women or patients with significant dose inhomogeneity 1

Boost Considerations

• Controversy exists regarding the need for an additional boost dose to the primary site 1
• When used, boost irradiation is typically delivered using electron beam or interstitial implantation 1
• A boost increases the total dose to the primary tumor site to approximately 6,000 to 6,600 cGy 1
• A boost may not be required for patients with clearly negative margins after more extensive breast resections 1
• If boost is omitted, the standard whole-breast radiation therapy dose should be 5,000 cGy at 200 cGy per fraction 1

Alternative Hypofractionated Regimens

• More recent evidence suggests hypofractionated regimens may be effective alternatives:
  • 42.5 Gy in 16 fractions (2.66 Gy per fraction) has shown excellent local control 2
  • Another approach uses 40.5-42 Gy in 15 fractions (2.7-2.8 Gy per fraction) with comparable outcomes to standard fractionation 3

Important Considerations and Precautions

• Nodal irradiation is unnecessary for patients with DCIS 1
• To minimize radiation pneumonitis risk, no more than 3-3.5 cm of lung should be treated 1
• For left-sided lesions, efforts should be made to minimize heart exposure in tangential fields 1
• Patient positioning and treatment planning should ensure reproducibility and dose homogeneity 1

Follow-up After Radiation

• Follow-up examinations should occur every 6 months for years 1-5, then annually thereafter 1
• Regular mammography is essential for early detection of recurrence 1
• Routine tests such as bone scans, chest x-rays, CT scans, and liver function tests are not indicated for asymptomatic patients 1