Response-Adapted Omission of Nodal Boost In N3 Breast Cancer After Neoadjuvant Systemic Therapy
Omitting the Boost to Initially Involved But Undissected Nodal Stations That Achieved Clinical Complete Response After Neoadjuvant Systemic Therapy in cN3 Breast Cancer: A Phase III Randomized Study
Background Clinical N3 (cN3) breast cancer represents a high-risk subgroup of locally advanced disease. After neoadjuvant systemic therapy (NST), patients who achieve a clinical complete response (cCR) in initially involved but undissected nodal stations currently receive a boost to these regions as part of standard postoperative radiotherapy. However, whether this boost is necessary in this setting remains unknown, and prospective evidence on the safety of boost omission is lacking.
Objective The REACT-N3 trial aims to evaluate whether omitting the boost to undissected nodal stations that achieve cCR after NST is non-inferior to standard boost in terms of 3-year invasive breast cancer recurrence-free interval (IBCRFI), while reducing toxicity to adjacent organs.
Methods This is an open-label, multicenter, randomized phase 3 trial. Eligible patients are women with cN3 breast cancer who have completed NST, undergone breast/axillary surgery with the internal mammary, supraclavicular, and infraclavicular nodes left undissected, and have no macroscopic residual disease in these stations on post-NST [¹⁸F]FDG PET-CT or other imaging. Participants will be randomized 1:1 to receive either a standard boost (10 Gy in 5 fractions) or no boost to the initially involved but cCR-converted undissected nodal stations. Randomization is stratified by postoperative axillary nodal status (ypN- vs. ypN+), location of the involved nodal station (SCV vs. non-SCV), and molecular subtype (TNBC vs. non-TNBC). The primary endpoint is 3-year IBCRFI. Secondary endpoints include locoregional recurrence-free survival, distant metastasis-free survival, disease-free survival, overall survival, toxicity, and patient-reported outcomes. With a non-inferiority margin of 8%, a one-sided α of 0.05, 80% power, and 10% drop-out rate, a total of 534 patients will be enrolled.
Discussion The REACT-N3 trial will provide high-level evidence on the safety of boost omission in cN3 breast cancer patients with cCR after NST. If non-inferiority is confirmed, this strategy could establish a new, toxicity-sparing standard for regional nodal irradiation in this high-risk population.
Study Overview
Status
Conditions
Intervention / Treatment
Study Type
Enrollment (Estimated)
Phase
- Not Applicable
Contacts and Locations
Study Locations
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Shanghai Municipality
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Shanghai, Shanghai Municipality, China, 200032
- Recruiting
- Fudan University Shanghai Cancer Center
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Contact:
- Jinli Ma, M.D., Ph.D.
- Phone Number: 86-21-64175590
- Email: ma-jinli@outlook.com
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Participation Criteria
Eligibility Criteria
Ages Eligible for Study
Accepts Healthy Volunteers
Genders Eligible for Study
Description
Inclusion Criteria:
- Female/male, aged 18-75 years.
- ECOG performance status 0-1.
- Histologically confirmed unilateral invasive breast cancer.
- No DM (M0), as confirmed by standard staging.
- cN3 disease, defined according to AJCC 8th staging system, confirmed by imaging and/or pathology, including any of the following: cN3a: metastasis to ipsilateral ICV nodes, with or without level I/II ALN involvement.
cN3b: metastasis to ipsilateral IMNs with concurrent level I/II ALN involvement.
cN3c: metastasis to ipsilateral SCV nodes, with or without ALN or IMN involvement.
Imaging confirmation is mandatory for all cN3 designations and may be performed using ultrasound, contrast-enhanced CT, MRI, or [18F]FDG PET-CT [16-18]. Across all modalities, abnormal features include, but are not limited to: abnormal enlargement (short-axis ≥5mm), rounded morphology with loss of the normal oval shape, solid appearance with effacement of the fatty hilum and cortical thickening, with or without irregular margins or necrosis. Modality-specific criteria include: heterogeneous enhancement on CT or MRI, or increased FDG uptake (SUVmax > mediastinal blood pool) on PET-CT. Pathological verification by fine-needle aspiration (FNA) or core needle biopsy (CNB) is recommended for SCV and ICV nodes when clinically feasible. If pathological confirmation is not obtained, the cN3 status is based solely on imaging criteria specified above.
- Completion of NST. Standard-of-care regimens must include at least four cycles of chemotherapy; Anti-HER2 targeted therapy is mandatory for HER2-positive disease, and immunotherapy may be added for eligible triple-negative breast cancer (TNBC). Clinical trial regimens are permitted per protocol, with or without chemotherapy, including novel agents (e.g., antibody-drug conjugates [ADCs], immunotherapies, anti-angiogenics, PARP inhibitors, or other investigational drugs). Both pathways are accepted provided the full protocol-specified course is completed.
- Underwent breast-conserving surgery (BCS) or mastectomy with levels I-II axillary lymph node dissection (ALND); IMN, SCV, and ICV nodes were left undissected. All surgical margins must be negative.
- Post-neoadjuvant imaging confirms no macroscopic residual disease in the initially involved but undissected nodal stations. The preferred modality is [18F]FDG PET-CT; ultrasound, contrast-enhanced CT or MRI are acceptable alternatives if PET-CT is unavailable. Imaging may be performed before or after surgery, but must be completed prior to randomization. For all modalities, cCR is defined as the complete disappearance of all previously involved but undissected lymph nodes. In cases where visible nodes persist on imaging, cCR may still be considered if: on PET-CT, no pathologic uptake; on ultrasound, CT, or MRI, nodes have normalized in size and morphology, and no suspicious features are present. Suspicious or equivocal findings require biopsy confirmation of negativity before randomization. All imaging studies must be interpreted by experienced radiologists using standardized criteria.
- Radiotherapy must start within 12 weeks of last surgery or last adjuvant chemotherapy cycle.
- Adjuvant systemic therapy per guidelines or trial protocols; investigational regimens require active trial enrollment.
- Written informed consent obtained.
Exclusion Criteria:
- Stage IV (metastatic) breast cancer.
- Prior or synchronous contralateral breast cancer.
- Macroscopic residual disease in the initially involved but undissected nodal stations (ICV, IMN, or SCV) in cN3 patients, as evidenced by post-neoadjuvant imaging and/or biopsy.
- Incomplete NST or no definitive breast/ALN surgery.
- Prior radiotherapy to the breast, CW, or regional nodes.
- History of other malignancies, except for adequately treated basal cell carcinoma of the skin or cervical carcinoma in situ (disease-free >3 years).
- Current pregnancy or lactation.
- Severe uncontrolled comorbidities (e.g., cardiac, hepatic, renal, or infectious) precluding radiotherapy, as judged by the investigator.
- Known intolerance or contraindication to radiotherapy or to the planned adjuvant systemic therapy (chemotherapy, endocrine therapy, anti HER2 therapy, or immunotherapy).
- Inability or unwillingness to comply with protocol requirements.
Study Plan
How is the study designed?
Design Details
- Primary Purpose: Treatment
- Allocation: Randomized
- Interventional Model: Parallel Assignment
- Masking: None (Open Label)
Arms and Interventions
Participant Group / Arm |
Intervention / Treatment |
|---|---|
|
Active Comparator: standard boost
a standard boost of 10Gy was delivered to the initially involved but undissected nodal stations that achieved clinical complete response |
a boost dose of 10 Gy in 5 fractions to initially involved but undissected nodal stations that achieved clincial complete response after neoadjuvant systemic therapy |
|
Experimental: boost omission
no boost was given to the initially involved but undissected nodal stations that achieved clinical complete response after neoadjuvant systemic therapy |
no boost to the initially involved but undissected nodal stations that achieved clinical complete response after neoadjuvant systemic therapy |
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Time Frame |
|---|---|
|
3-year invasive breast cancer (IBC) recurrence-free interval (RFI)
Time Frame: 3-year
|
3-year
|
Collaborators and Investigators
Sponsor
Study record dates
Study Major Dates
Study Start (Actual)
Primary Completion (Estimated)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Keywords
Additional Relevant MeSH Terms
Other Study ID Numbers
- FDRT-BC-N3
Plan for Individual participant data (IPD)
Plan to Share Individual Participant Data (IPD)?
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
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