What are the recommended volumes of radiation therapy for a 50-year-old lady with right-sided LABC, post-MRM and ALND, who is triple positive with pT3N1 disease, after completing adjuvant chemotherapy?

Radiation Therapy Volumes for Post-MRM Triple-Positive Breast Cancer with 1-3 Positive Nodes

For a 50-year-old woman with right-sided locally advanced breast cancer (LABC), pT3N1 disease with 2/12 positive nodes without extracapsular extension who has completed adjuvant chemotherapy after MRM+ALND, the recommended radiation therapy volumes should include chest wall, supraclavicular, infraclavicular, and internal mammary nodal regions. 1, 2

Rationale for Comprehensive Nodal Irradiation

Chest Wall Irradiation

• Chest wall irradiation is strongly indicated due to:
  • T3 tumor size (>5 cm)
  • Positive axillary lymph nodes (pN1)
  • Locally advanced breast cancer status

Regional Nodal Irradiation

• Supraclavicular and infraclavicular regions:

  • Strong recommendation for inclusion in patients with 1-3 positive nodes 1
  • Reduces locoregional recurrence risk and improves disease-free survival 1

• Internal mammary nodes:

  • Strong consideration recommended (category 2B) for patients with positive axillary nodes 1
  • Results from NCIC-CTG MA.20 trial showed significant benefits in disease-free survival with regional node irradiation 1

Evidence Supporting Comprehensive Nodal Irradiation

The NCCN guidelines recommend postmastectomy radiation therapy for women with 1-3 involved axillary lymph nodes and tumors larger than 5 cm (as in this case with T3 disease) 1. This should include radiation to the chest wall and supraclavicular area.

The ASCO/ASTRO/SSO focused guideline update specifically addresses this clinical scenario, recommending treatment generally be administered to both the internal mammary nodes and the supraclavicular-axillary apical nodes in addition to the chest wall 1.

The Early Breast Cancer Trialists' Collaborative Group meta-analysis showed 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.

Technical Aspects

• Recommended radiation dose:

  • 45-50 Gy in fractions of 1.8-2.0 Gy to the chest wall, mastectomy scar, and drain sites 1
  • Alternative hypofractionated regimen: 42.5 Gy in fractions of 2.55 Gy 1
  • Consider boost dose of 10-16 Gy for high-risk patients (patient is 50 years old) 1

• CT-based treatment planning is essential to:

  • Ensure adequate target coverage
  • Minimize radiation dose to heart and lungs 1, 2

Prognostic Considerations

The triple-positive status of this patient's tumor has implications for treatment response and outcomes. Studies show that HER2-positive tumors may have better response to systemic therapy but can still benefit from comprehensive radiation therapy 3, 4.

Potential Pitfalls to Avoid

1. Omitting internal mammary nodes: While some controversy exists, current guidelines recommend strong consideration of internal mammary field radiation therapy in patients with positive axillary nodes 1, 2.

2. Inadequate coverage of supraclavicular region: The optimal supraclavicular target volume should include the most caudal lymph nodes surrounding the subclavicular arch and the base of the jugular vein 2.

3. Unnecessary irradiation of dissected axilla: After adequate axillary lymph node dissection, the resected part of the axilla should not be irradiated except in cases of clear residual disease after surgery 2.

4. Ignoring cardiac sparing techniques: Given the right-sided location, cardiac sparing is less critical but still important for long-term survival outcomes.

By following these comprehensive radiation therapy recommendations, this patient will receive optimal treatment to reduce the risk of locoregional recurrence and improve overall survival.