Radiation Therapy Indications After Breast Surgery
Radiation therapy is strongly recommended after breast-conserving surgery (BCS) for invasive breast cancer, while post-mastectomy radiation is indicated for patients with ≥4 positive nodes, T3-T4 tumors, or 1-3 positive nodes with additional risk factors. 1
After Breast-Conserving Surgery (BCS)
Invasive Breast Cancer
- Whole breast radiation therapy (WBRT) is strongly recommended after BCS for invasive cancer 1
- WBRT reduces local recurrence risk by two-thirds and improves survival 1
- Standard dose: 45-50 Gy in 25-28 fractions OR hypofractionated 15-16 fractions with 2.5-2.67 Gy per fraction 1
Boost Radiation to Tumor Bed
- Boost irradiation provides an additional 50% reduction in local recurrence risk 1
- Strongly indicated for patients with unfavorable risk factors: 1
- Typical boost dose: 10-16 Gy in 2 Gy fractions 1
- In patients >40 years with wide margins, node-negative disease, and no vessel invasion, boost may be optional 1
Exceptions Where Radiation May Be Omitted After BCS
- Patients >70 years with: 1
- Hormone receptor-positive disease
- pT1N0 (≤2 cm, node-negative)
- Clear surgical margins
- Receiving adjuvant endocrine therapy
- Highly selected luminal A subtype patients ≥55 years with: 3
- T1N0, grade 1-2 disease
- ER+ (≥1%), PR+ (>20%), HER2-negative
- Ki67 ≤13.25%
- Receiving endocrine therapy
- 5-year local recurrence rate of 2.3% without radiation 3
DCIS (Non-Invasive Carcinoma)
- Adjuvant WBRT after BCS for DCIS decreases local recurrence risk but does not affect survival 1
- Radiation may be omitted in highly selected low-risk DCIS: tumor <10 mm, low/intermediate nuclear grade, adequate margins (>2 mm) 1
- Boost radiation can be considered for higher-risk DCIS patients (e.g., young age) 1
After Mastectomy
Clear Indications for Post-Mastectomy Radiation Therapy (PMRT)
- ≥4 positive axillary lymph nodes 1
- T3-T4 tumors (>5 cm or chest wall/skin involvement), independent of nodal status 1
Consider PMRT in Intermediate-Risk Patients
PMRT should be considered for patients with 1-3 positive axillary nodes, particularly when additional risk factors are present: 1
- Young age
- Vascular/lymphovascular invasion
- Low number of examined axillary lymph nodes
- T2 tumors (2-5 cm), especially if medially located
- Grade 3 histology
- Hormone receptor-negative disease
- HER2-positive disease
- High proliferation markers (e.g., high Ki67)
PMRT Not Indicated
- DCIS treated with mastectomy and clear margins does not require radiation 1
- Node-negative, T1-T2 tumors without high-risk features typically do not require PMRT 1
Regional Nodal Irradiation
- Supraclavicular nodes should be included when: 1
- Extensive axillary involvement (N≥2)
- Multiple positive nodes
- Internal mammary nodes should be included when: 1
- Documented metastatic spread to this region
- Medial or central tumor location with axillary node involvement 1
- Axillary irradiation after complete axillary dissection should be avoided to minimize complications (lymphedema, fibrosis) unless residual disease is present 1
Important Caveats
- Timing: Radiation should begin as soon as possible after surgery, ideally within 12 weeks, except when preceded by chemotherapy 4
- Sequencing with chemotherapy: Most centers administer chemotherapy before radiotherapy to avoid delays in systemic therapy 4
- Hypofractionation: Shorter fractionation schemes (15-16 fractions) are validated and generally recommended, though data are limited in young patients and those receiving regional nodal irradiation 1
- Partial breast irradiation (PBI/APBI): Should only be used in carefully selected patients ≥50 years with unicentric, unifocal, node-negative, non-lobular cancer ≤3 cm without extensive intraductal component or lymphovascular invasion 1