Radiation Therapy for Unilateral DCIS After Lumpectomy
Whole breast radiation therapy (WBRT) using opposed tangential photon fields is the standard radiation treatment for unilateral DCIS after lumpectomy, delivered at a dose of 4,500-5,000 cGy in 180-200 cGy fractions. 1
Standard Radiation Technique
Whole Breast Radiation
- WBRT encompasses the tumor bed, surrounding tissue, and most of the ipsilateral breast using paired tangential photon fields 1
- Conventional fractionation: 45-50 Gy in 25-28 fractions of 1.8-2.0 Gy 1
- Hypofractionation (preferred approach for most patients): 42.5 Gy in 16 fractions (2.66 Gy per fraction) 1, 2
- Hypofractionated regimens have shown excellent local control with 97% local recurrence-free survival at 5 years 2
Boost Considerations
- A boost to the tumor bed may be considered for patients at higher risk for local recurrence 1, 3
- When used, boost irradiation is typically delivered using:
- Boost may not be required for patients with more extensive breast resections and clearly negative margins 1
Technical Considerations
Treatment Planning
- Radiation should begin within 2-4 weeks after uncomplicated breast-conserving surgery 1
- Treatment delivered daily (Monday through Friday) 1
- Bolus should not be used 1
- Measures to ensure reproducibility of patient setup, treatment simulation, and planning are essential 1
- For left-sided lesions, efforts should be made to minimize the amount of heart in tangential fields 1
Equipment Selection
- Standard supervoltage equipment should be used to ensure dose homogeneity 1
- Higher energy photons (≥10 MV) may be indicated for very large-breasted women or patients with significant dose inhomogeneity (≥10%) 1
Techniques to Avoid
- Nodal irradiation is unnecessary for patients with DCIS 1, 3
- Excess dose to the heart or lungs through tangential irradiation must be avoided 1
- Three-dimensional dose distributions are not considered standard for routine DCIS treatment 1
Patient Selection Considerations
- WBRT after BCS for DCIS decreases the risk of local recurrence by approximately 50% 3, 4
- Risk factors for recurrence include:
- Positive surgical margins
- High nuclear grade
- Age less than 50 years
- Premenopausal status 2
Follow-up Care
- Clinical examinations every 6 months for years 1-5, then annually thereafter 1, 3
- Annual mammography (first mammogram 6-12 months post-radiation if breast conserved) 3
Special Considerations
- Clear margins of at least 2 mm should be ensured to minimize local recurrence risk 1, 3
- For select low-risk DCIS (tumor size <10 mm, low/intermediate nuclear grade, adequate surgical margins), omitting radiation may be an option, though this remains controversial 1, 5
Radiation therapy significantly reduces the risk of ipsilateral breast tumor recurrence in DCIS, with approximately half of untreated recurrences developing as invasive cancer 6, 4. The choice between conventional and hypofractionated regimens should be based on patient characteristics, with hypofractionation increasingly preferred for most patients due to its excellent outcomes and shorter treatment course.