Radiation Oncology/Breast/Neoadjuvant chemotherapy

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Radiation Considerations After Neoadjuvant Chemotherapy

cN+ => ypN0

  • NSABP B-51 (2013-2020) -- Adjuvant RNI vs observation
    • Randomized. 1641 patients Protocol Schema. cT1-T3N1, s/p NACT x8+ weeks, with radiographic cN0, s/p mastectomy (42%) or BCS (58%), SLNB 55%. Median age 52, ER+/HER2- 21%, ER+/HER2+ 32%, ER-/HER2+ 25%, ER-/HER2-21%. Arm 1) Regional nodal radiation 60/25 to include SCL and IM nodes vs Arm 2) Observation (tangent radiation if lumpectomy). Boost 12-14/6-7 fractions at discretion.
    • 2023 https://ascopost.com/issues/february-25-2024/some-patients-with-breast-cancer-may-safely-avoid-locoregional-irradiation-after-neoadjuvant-chemotherapy/ San Antonio Abstract]
      • Outcome: 5-year RFS RNI 92.7% vs OBS 91.8% (NS), similar LR-RFS, D-RFS, DFS, and OS
    • 2025 PMID 40466065 -- "Omitting Regional Nodal Irradiation after Response to Neoadjuvant Chemotherapy" (Mamounas E, N Engl J Med. 2025 Jun 5;392(21):2113-2124. doi: 10.1056/NEJMoa2414859.) Median F/U 5 years
      • Outcome: 5-year EFS RNI 92.7% vs no RNI 91.8% (NS). LR-RFS 98.9% vs 98.4% (HR 0.57, NS). D-RFS 88.3% vs 88.5% (HR 1.06, NS). OS 93.6% vs 94.0% (HR 1.12, NS)
      • Subgroup analysis: Lumpectomy HR 1.08 vs Mastectomy HR 0.72; ER- 1.12 vs ER+ 0.66; HER2- 1.01 vs HER2+ 0.77; triple negative 2.30 vs ER-/HER2+ 0.63 vs ER+/HER2+ 0.63 vs ER+/HER2- 0.41; pCR+ 0.74 vs pCR- 0.93; age <49 1.39 vs age 50-59 0.52 vs age >60 0.96; black 0.70 vs white 1.00; ALND 1.02 vs SLNB alone 0.75
      • Toxicity: Grade 3 RNI 10 vs no RNI 6.5%; most common radiation dermatitis 5.7% vs 3.3%
      • Conclusion: Addition of adjuvant nodal RT did not decrease risk of invasive breast cancer recurrence in patients with negative lymph nodes after neoadjuvant chemotherapy

ypN+

Residual nodal burden

  • Barcelona; 2024 PMID 39518078 --"Predicting Additional Metastases in Axillary Lymph Node Dissection After Neoadjuvant Chemotherapy: Ratio of Positive/Total Sentinel Nodes" (Cebrecos I, Cancers (Basel). 2024 Oct 29;16(21):3638. doi: 10.3390/cancers16213638.)
    • Retrospective. 118 patients, cN0-N1, ypN+ by SLN/TAD, with subsequent ALND. Residual disease 39 (33%).
    • Outcome: Lymph node ration <0.35 cut-off, with False Negative 10%
    • Conclusion: SLN ratio is a valuable predictor for omission of ALND
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