What are the guidelines for breast radiation therapy, including hypofractionation (HF), ultrahypofractionation (UH), omission of radiation, and Accelerated Partial Breast Irradiation (APBI)?

Guidelines for Breast Radiation Therapy

Hypofractionated whole-breast radiotherapy (40-42.5 Gy in 15-16 fractions) is now the preferred standard of care for patients after breast-conserving surgery, offering equivalent or better outcomes in terms of local control, cosmesis, and reduced toxicity compared to conventional fractionation. 1

Whole Breast Radiation Therapy (WBRT)

Standard Approaches

• Conventional fractionation: 46-50 Gy in 23-25 fractions over 5 weeks 1
• Hypofractionation (preferred): 40-42.5 Gy in 15-16 fractions over 3 weeks 1
• Ultra-hypofractionation: 26 Gy in 5 daily fractions for whole-breast or chest wall (without reconstruction) irradiation 1

Evidence Supporting Hypofractionation

• The START-B trial demonstrated that 40 Gy in 15 fractions produced equivalent local control with fewer normal tissue effects compared to 50 Gy in 25 fractions 2, 3
• The Canadian trial showed that 42.5 Gy in 16 fractions was equivalent to conventional fractionation 1
• The DBCG HYPO trial confirmed non-inferiority of 40 Gy in 15 fractions with 9-year locoregional recurrence rates of 3.0% vs 3.3% for standard fractionation 4

Boost to Tumor Bed

• Recommended for patients with higher risk of recurrence: 1
  • Age <50 years
  • High-grade disease
  • Focally positive margins
• Typical boost doses: 10-16 Gy in 4-8 fractions 1
• Can be delivered using brachytherapy, electron beam, or photon fields 1

Accelerated Partial Breast Irradiation (APBI)

APBI is an alternative to WBRT for select patients with low risk of recurrence 1.

Patient Selection Criteria

• ASTRO guidelines determine suitability 1
• Generally appropriate for:
  • Women ≥60 years old
  • Not carriers of BRCA1/2 mutation
  • Unifocal T1N0 ER-positive cancer
  • Infiltrating ductal or favorable histology
  • No extensive intraductal component or LCIS
  • Negative margins 1

APBI Dosing

• 34 Gy in 10 fractions delivered twice per day with brachytherapy
• 38.5 Gy in 10 fractions delivered twice per day with external-beam photon therapy 1

Regional Nodal Irradiation

Indications Based on Nodal Status

• 4+ positive lymph nodes after lumpectomy: WBRT with regional nodal irradiation (category 1) 1
• 4+ positive lymph nodes after mastectomy: Chest wall RT plus regional nodal irradiation (category 1) 1
• 1-3 positive lymph nodes after lumpectomy: WBRT with consideration of regional nodal irradiation based on risk 1
• 1-3 positive lymph nodes after mastectomy: Consider chest wall RT plus regional nodal irradiation 1

Regional Nodal Volumes

• Supraclavicular area
• Infraclavicular region
• Internal mammary nodes
• Any part of axillary bed considered at risk 1

Dose

• 46-50 Gy in 23-25 fractions to regional nodal fields 1

Omission of Radiation Therapy

Omission of RT is acceptable in select patients with lower risk of recurrence:

• Patients ≥70 years old
• ER-positive, clinically node-negative
• T1 tumors
• Receiving adjuvant endocrine therapy (category 1) 1

Special Considerations

Post-Mastectomy Radiation Therapy (PMRT)

• Recommended for high-risk features: involved margins, 4+ involved lymph nodes, T3-T4 tumors 1
• Consider for intermediate-risk features including 1-3 positive nodes 1
• Hypofractionation not routinely recommended in post-mastectomy setting 1

Radiation After Neoadjuvant Therapy

• Decisions should be based on pre-chemotherapy tumor characteristics, regardless of response to therapy 1
• Surgical planning following pre-surgical therapy should consider post-treatment situation 1

Practical Considerations and Caveats

• CT-based treatment planning is recommended to ensure adequate target coverage and limit dose to normal tissues, especially heart and lungs 1
• Hypofractionation should not be routinely used when treating regional nodes 1
• For patients receiving adjuvant chemotherapy, radiation should be given after chemotherapy is completed 1
• Moderate and ultra-hypofractionated schedules have shown excellent results with reduced normal tissue effects including breast shrinkage, telangiectasia, and breast edema 2

By following these evidence-based guidelines for breast radiation therapy, clinicians can optimize local control while minimizing toxicity and improving quality of life for breast cancer patients.