What is the role of elective supraclavicular fossa (SCF) irradiation in patients with pathologically positive lymph node (pN+) breast cancer after modified radical mastectomy (MRM) or wide local excision (WLE) plus axillary lymph node dissection (ALND) according to the latest National Comprehensive Cancer Network (NCCN) and American Society for Radiation Oncology (ASTRO) guidelines?

Elective Supraclavicular Fossa Irradiation in pN+ Breast Cancer After MRM/WLE+ALND

Comprehensive nodal radiotherapy including the supraclavicular fossa (SCF) is strongly recommended for all patients with pathologically node-positive breast cancer after MRM or WLE+ALND, regardless of the number of positive nodes, to reduce locoregional recurrence risk and improve survival outcomes. 1

Indications Based on Nodal Status

Patients with ≥4 Positive Nodes

• Category 1 recommendation (highest level of evidence) for post-mastectomy radiotherapy (PMRT) including chest wall and regional nodal irradiation (RNI) 1
• PMRT reduces 10-year risk of any recurrence by 10% and 20-year breast cancer mortality by 8% 1
• Target volumes should include:
  • Ipsilateral chest wall/breast
  • Supraclavicular fossa
  • Infraclavicular region
  • Internal mammary nodes 1

Patients with 1-3 Positive Nodes

• Strong recommendation for PMRT including SCF irradiation 1
• EBCTCG meta-analysis shows that radiotherapy after mastectomy and axillary node dissection reduced both recurrence and breast cancer mortality in women with 1-3 positive lymph nodes, even when systemic therapy was administered 1
• The Danish Breast Cancer Cooperative Group studies showed substantial survival benefit with PMRT including regional nodal irradiation for women with 1-3 positive nodes 1

Target Volume Considerations

The optimal SCF target volume should include:

• Most caudal lymph nodes surrounding the subclavicular arch
• Base of the jugular vein 1
• CT-based treatment planning is recommended to ensure adequate target coverage while limiting dose to normal tissues, especially heart and lungs 1, 2

Evidence Supporting SCF Irradiation

• ESMO guidelines recommend comprehensive nodal RT for patients with involved lymph nodes (Level I, B evidence) 1
• NCCN guidelines recommend irradiation of infraclavicular and supraclavicular areas, internal mammary nodes, and any part of the axillary bed at risk (Category 1 for ≥4 positive nodes; 2A for 1-3 positive nodes) 1
• The MA.20 trial demonstrated that adding regional nodal irradiation (including SCF) to whole-breast radiation reduced locoregional and distant recurrence and improved disease-free survival (HR, 0.76; 95% CI, 0.61-0.94; P=0.01) 3

Special Considerations

• After ALND, the resected part of the axilla should not be irradiated except in cases of clear residual disease after surgery 1
• For patients with positive sentinel lymph node biopsy without subsequent ALND, regional RT including SCF is advised 1
• The extent of axillary lymph node levels to be irradiated should be based on risk factors including:
  • Extent of nodal involvement
  • Tumor diameter
  • Tumor grade
  • Vascular invasion
  • Tumor site 1

Potential Risks and Benefits

• Benefits: Reduced locoregional recurrence by 8-15% and improved disease-free survival 4, 3
• Risks: Increased rates of lymphedema (8.4% vs 4.5%) and grade 2 or greater acute pneumonitis (1.2% vs 0.2%) 3

Clinical Implementation

For patients with pN+ breast cancer after MRM/WLE+ALND, the algorithm for SCF irradiation is:

1. All patients with ≥4 positive nodes: Include SCF in radiation fields (Category 1)
2. All patients with 1-3 positive nodes: Include SCF in radiation fields (Strong recommendation)
3. For patients with pN1mi or isolated tumor cells: Consider SCF irradiation only with additional high-risk features 5

The evidence strongly supports the inclusion of SCF in the radiation treatment fields for all node-positive breast cancer patients after MRM or WLE+ALND to optimize locoregional control and survival outcomes.