Response-Adapted Omission of Nodal Boost In N3 Breast Cancer After Neoadjuvant Systemic Therapy

NCT07829848 | Recruiting DMC

• 1 other identifier: FDRT-BC-N3
• Study Type: interventional
• Target: 534
• Locations: 1 country
• Sites: 1

Brief Summary

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.

Conditions

Breast Cancer

Keywords

Clinical N3 breast cancer; neoadjuvant systemic therapy; clinical complete response; regional nodal irradiation; boost omission

Outcome Measures

Primary Outcomes (1)

• 3-year invasive breast cancer (IBC) recurrence-free interval (RFI)

  3-year

Study Arms (2)

standard boost

ACTIVE COMPARATOR

a standard boost of 10Gy was delivered to the initially involved but undissected nodal stations that achieved clinical complete response

Radiation: standard boost

boost omission

EXPERIMENTAL

no boost was given to the initially involved but undissected nodal stations that achieved clinical complete response after neoadjuvant systemic therapy

Radiation: boost omission

Interventions

standard boost RADIATION

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

standard boost

boost omission RADIATION

no boost to the initially involved but undissected nodal stations that achieved clinical complete response after neoadjuvant systemic therapy

boost omission

Eligibility Criteria

• Age: 18 Years - 75 Years
• Sex: all
• Healthy Volunteers: No
• Age Groups: Adult (18-64), Older Adult (65+)

You may qualify if:

• 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.

You may not qualify if:

• 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.

Sponsors & Collaborators

• Fudan University: lead

Study Sites (1)

Fudan University Shanghai Cancer Center

Shanghai, Shanghai Municipality, 200032, China

RECRUITING

MeSH Terms

Conditions

Breast Neoplasms

Condition Hierarchy (Ancestors)

Neoplasms by Site; Neoplasms; Breast Diseases; Skin Diseases; Skin and Connective Tissue Diseases

Study Design

• Study Type: interventional
• Phase: not applicable
• Allocation: RANDOMIZED
• Masking: NONE
• Purpose: TREATMENT
• Intervention Model: PARALLEL
• Sponsor Type: OTHER
• Responsible Party: PRINCIPAL INVESTIGATOR
• PI Title: Clinical Professor

Study Record Dates

• First Submitted: September 15, 2026
• First Posted: September 21, 2026
• Study Start: September 12, 2026
• Primary Completion (Estimated): September 12, 2030
• Study Completion (Estimated): September 12, 2033
• Last Updated: September 23, 2026

Record last verified: 2026-09

Data Sharing

• IPD Sharing: Will not share

Locations

CN (1)