Maximizing Control Via Radiation in High-Risk and Recurrent Breast Cancer

At the ACRO 2026 Radiation Oncology Summit, J. Isabelle Choi, MD, presented a comprehensive overview of strategies to improve outcomes in locoregionally advanced or recurrent breast cancer.¹ As advances in early detection and multimodality therapy improve overall survival, clinicians are increasingly encountering the challenge of managing isolated locoregional recurrences (iLRR) and high-risk nodal involvement. Choi’s presentation offered actionable guidance for radiation oncologists on dose escalation for internal mammary nodes (IMN) and supraclavicular (SCV) nodes, as well as technical and clinical considerations for safe breast reirradiation. Here are the top 5 takeaways for radiation oncologists based on her presentation.

Choi is an associate attending radiation oncologist at Memorial Sloane Kettering Cancer Center.

1. Implement Selective Boosting for Clinically Involved Nodal Basins

For patients with locoregionally advanced disease, undissected and clinically involved nodal basins—specifically the IMN and supraclavicular SCV fossa—should receive a radiation boost during adjuvant therapy.

• Complete Response (CR) to Neoadjuvant Chemotherapy: A 10 Gy boost is recommended for patients who achieve a radiographic or clinical CR.
• Residual Disease: For residual disease after neoadjuvant chemotherapy, the boost dose should be escalated to 14 Gy to 20 Gy.
• Outcomes: Data from MD Anderson show that implementing these boosts (10 Gy for CR; 16 Gy for residual disease) resulted in a 5-year local-regional recurrence-free survival of 89%, with only approximately 2% IMN failures.²

2. Delineate Nodal Targets Using Pre-Treatment Imaging

Precise treatment planning requires the localization and delineation of involved nodes using all available clinical data, including pre-neoadjuvant chemotherapy CT, MRI, and PET scans.

• IMN Volume: Coverage should include the involved interspace plus 1 interspace above and below. Standard coverage typically involves the first 3 intercostal spaces, but more inferior coverage up to the 5th interspace is necessary if lower nodes were involved.

3. Prioritize Comprehensive Fields for High-Risk Recurrences

When treating breast cancer recurrence, particularly in the chest wall (CW) or regional lymph nodes, a comprehensive treatment approach is more favorable rather than limited "involved field" reirradiation.

• Comprehensive Reirradiation: This approach typically includes the breast or chest wall plus the regional lymph nodes.
• Clinical Rationale: Recurrences are often treatment-refractory and associated with high-risk features like lymphovascular invasion or dermal lymphatic invasion.
• Outcomes: MSK data on comprehensive photon reirradiation showed a local recurrence rate of 5.6%, a regional recurrence rate of 8.9%, a distant recurrence rate of 27.0%, and overall survival rate of 82% at a median follow-up of 63 months.³

4. Respect Cumulative Dose Constraints for Critical Organs

Reirradiation is a high-risk procedure where cumulative doses often exceed standard constraints. Clinicians must meticulously track dose-volume histograms (DVH) from both treatment courses.

• Brachial Plexus: The cumulative maximum dose should ideally be kept below 75 Gy to 85 Gy to minimize the risk of plexopathy.
• IMN Modality: Strong consideration should be given to highly conformal techniques, such as IMRT/VMAT or proton therapy, to spare the heart and lungs.
• Toxicity Awareness: Patients must be counseled on risks such as rib fractures (late grade 2 events were observed in approximately 6.1% of MSK photon cases), chest wall pain, and reconstruction failure in patients with implants.³

5. Adopt an Individualized, Multidisciplinary Approach

There is currently a lack of standardization in reirradiation, making individualized treatment plans essential.

• Treatment Interval: Use caution if the interval between radiation courses is less than 1 year.
• Salvage Strategy: Management should include a discussion of maximal surgical resection and systemic therapy alongside radiation.
• For limited in-breast recurrence, repeat breast cancer therapy should be considered.
• For high in-breast recurrence, CW/isolated lymph node recurrence should be considered.
• Managing Toxicities: Clinicians should be prepared to manage and follow acute long-term toxicities. These may include long-term skin care, daily massages, or vitamin E.

References

1. Choi I. Improving outcomes in locoregionally advanced or recurrent breast cancer. Presented at ACRO 2026 Radiation Oncology Summit, Orlando, FL; February 5, 2026.
2. Andring LM, Diao K, Sun S, et al. Locoregional management and prognostic factors in breast cancer with ipsilateral internal mammary and axillary lymph node involvement. Int J Radiat Oncol Biol Phys. 2022;113(3):552-560. doi:10.1016/j.ijrobp.2022.02.037
3. Chakraborty MA, White C, Zhang Z, et al. 1082 - Curative-intent photon reirradiation for local-regional breast cancer recurrence. Int J Radiat Oncol Biol Phys. 2025;123(1):S214. doi:10.1016/j.ijrobp.2025.07.1320