Internal Mammary Node Irradiation After Neoadjuvant Systemic Therapy for Breast Cancer (IMN-Neo)

November 3, 2026 updated by: Mahidol University

Internal Mammary Node Irradiation Versus Omission of Internal Mammary Node Irradiation in Breast Cancer Treated With Neoadjuvant Systemic Therapy: A Phase III Multicenter Randomized Trial

This multicenter randomized controlled trial evaluates whether internal mammary node irradiation (IMNI) improves oncologic outcomes in patients with breast cancer who have residual pathologically positive lymph nodes after neoadjuvant systemic therapy.

Eligible participants will be randomly assigned in a 1:1 ratio to receive locoregional radiotherapy either with or without irradiation of the internal mammary lymph nodes. The primary outcome is disease-free survival. Secondary outcomes include overall survival, breast cancer mortality, locoregional recurrence-free survival, distant metastasis-free survival, and treatment-related toxicity, particularly cardiac and pulmonary toxicity.

A total of 1,760 participants are planned to be enrolled across multiple centers in Thailand.

Study Overview

Status

Status

Indicates the current recruitment status or the expanded access status.
Not yet recruiting

Conditions

Conditions

The disease, disorder, syndrome, illness, or injury that is being studied. On ClinicalTrials.gov, conditions may also include other health-related issues, such as lifespan, quality of life, and health risks.

Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.

Detailed Description

Regional nodal irradiation is an established component of adjuvant radiotherapy for selected patients with node-positive breast cancer. However, the additional benefit of internal mammary node irradiation (IMNI) remains uncertain, particularly in patients receiving contemporary neoadjuvant systemic therapy. Although previous randomized trials have demonstrated potential oncologic benefits of regional nodal irradiation incorporating IMNI, most were conducted in patients undergoing upfront surgery, before the widespread use of modern systemic treatments. Consequently, the benefit-risk balance of IMNI in patients with residual nodal disease after neoadjuvant systemic therapy remains unclear.

IMN-Neo is a phase III, multicenter, randomized, open-label superiority trial designed to evaluate whether the addition of IMNI to standard locoregional radiotherapy improves oncologic outcomes in patients with residual pathologically positive axillary lymph nodes following neoadjuvant systemic therapy.

Participants will be randomized in a 1:1 ratio using computer-generated mixed block randomization, stratified by pathological nodal stage, method of axillary evaluation, primary tumor location, and breast cancer molecular subtype. Randomization will be performed at the time of radiotherapy simulation.

Both treatment groups will receive radiotherapy to the breast or chest wall and regional lymph nodes according to protocol-defined target delineation and dose constraints. The experimental group will additionally receive irradiation of the internal mammary lymph nodes, encompassing the first through third intercostal spaces, whereas the control group will undergo intentional omission of IMNI. Three-dimensional conformal radiotherapy or more advanced techniques will be used, with deep inspiration breath-hold permitted to minimize radiation exposure to surrounding normal tissues.

Participants will undergo scheduled clinical follow-up to assess disease recurrence, survival, and treatment-related adverse effects. Particular attention will be given to cardiac and pulmonary toxicity because of the potential increase in radiation exposure associated with IMNI.

An independent Data and Safety Monitoring Board will oversee participant safety and trial conduct. A prespecified interim efficacy analysis will be performed after approximately 50% of the required primary endpoint events have occurred, with additional monitoring for unexpected oncologic harm and serious treatment-related toxicity.

The trial aims to provide prospective evidence to guide individualized decision-making regarding IMNI in patients with residual nodal disease following contemporary neoadjuvant systemic therapy.

Study Type

Study Type

Describes the nature of a clinical study. Study types include interventional studies (also called clinical trials), observational studies (including patient registries), and expanded access.
Interventional

Enrollment (Estimated)

Enrollment

The number of participants in a clinical study. The "anticipated" enrollment is the target number of participants that the researchers need for the study.
1760

Phase

Phase

The stage of a clinical trial studying a drug or biological product, based on definitions developed by the U.S. Food and Drug Administration (FDA). The phase is based on the study's objective, the number of participants, and other characteristics. There are five phases: Early Phase 1 (formerly listed as Phase 0), Phase 1, Phase 2, Phase 3, and Phase 4. Not Applicable is used to describe trials without FDA-defined phases, including trials of devices or behavioral interventions.
  • Phase 3

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Contact

Study Contact

The name and contact information for the person who can answer enrollment questions for a clinical study. Each location where the study is being conducted may also have a specific contact, who may be better able to answer those questions.

Study Locations

  • Thailand
      • Bangkok, Thailand
        • Chulabhorn Hospital
        • Contact:
        • Sub-Investigator:
          • Areeya Tinsurawattana, MD
      • Chon Buri, Thailand
        • Chonburi Cancer Hospital
        • Contact:
      • Chon Buri, Thailand
        • Vibharam Amata Nakorn Cancer Hospital
        • Contact:
      • Lopburi, Thailand
        • Lop Buri Cancer Hospital
        • Contact:
      • Nakhon Pathom, Thailand
        • Synphaet Hospital Nakhon Pathom
        • Contact:
      • Nakhon Si Thammarat, Thailand
        • Maharaj Nakhon Si Thammarat Hospital
        • Contact:
      • Ratchaburi, Thailand
        • Ratchaburi Hospital
        • Contact:
      • Samut Sakhon, Thailand
        • Metropolitan Hospital Tha Chalom, Samut Sakhon Hospital
        • Contact:
    • Bangkok Noi
      • Bangkok, Bangkok Noi, Thailand, 10700
        • Siriraj Hospital
        • Contact:
        • Principal Investigator:
          • Tanun Jitwatcharakomol, MD
        • Sub-Investigator:
          • Pittaya Dankulchai, MD
        • Sub-Investigator:
          • Janjira Petsuksiri, MD
        • Sub-Investigator:
          • Chinnavuth Vatanashevanopakorn, MD
        • Sub-Investigator:
          • Pongpop Tuntapakul, MD
        • Sub-Investigator:
          • Wiwatchai Sittiwong, MD
        • Sub-Investigator:
          • Ratchapas Romrattaphan, MD
        • Sub-Investigator:
          • Krittee Chesdachai, MD

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Eligibility Criteria

The key requirements that people who want to participate in a clinical study must meet or the characteristics they must have. Eligibility criteria consist of both inclusion criteria (which are required for a person to participate in the study) and exclusion criteria (which prevent a person from participating). Types of eligibility criteria include whether a study accepts healthy volunteers, has age or age group requirements, or is limited by sex.

Ages Eligible for Study

18 years and older (Adult, Older Adult)

Accepts Healthy Volunteers

No

Genders Eligible for Study

Female

Description

Inclusion Criteria:

  • Histologically confirmed breast cancer with pathologically proven lymph node positivity after neoadjuvant systemic therapy.
  • Received neoadjuvant chemotherapy and/or targeted therapy and/or immunotherapy before surgery.
  • Underwent either breast-conserving surgery or mastectomy with lymph node evaluation and is planned to receive adjuvant locoregional radiotherapy.
  • Planned treatment with three-dimensional conformal radiotherapy (3D-CRT) or a more advanced radiotherapy technique.
  • Female ≥ 18 years

Exclusion Criteria:

  • Clinical or radiologic evidence of internal mammary lymph node involvement of any size.
  • Inflammatory breast cancer.
  • Bilateral breast cancer.
  • Multiple primary malignancies, except basal cell carcinoma and premalignant gynecologic lesions including CIN, HSIL, LSIL, VIN, and VAIN.
  • Prior chest irradiation.
  • Disease progression before radiotherapy.
  • Metastatic disease (M1) according to the AJCC 8th edition.

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

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

Participant Group / Arm

A group or subgroup of participants in a clinical trial that receives a specific intervention/treatment, or no intervention, according to the trial's protocol.
Intervention / Treatment

Intervention / Treatment

A process or action that is the focus of a clinical study. Interventions include drugs, medical devices, procedures, vaccines, and other products that are either investigational or already available. Interventions can also include noninvasive approaches, such as education or modifying diet and exercise.
Experimental: IMNI Group

Participants will receive adjuvant locoregional radiotherapy including irradiation of the internal mammary lymph nodes.
Radiation: Locoregional Radiotherapy With Internal Mammary Node Irradiation

Adjuvant locoregional radiotherapy to the breast or chest wall and regional lymph nodes, including the internal mammary lymph nodes. Allowed dose-fractionation schedules include 50 Gy in 25 fractions, 42.5 Gy in 16 fractions, or 40 Gy in 15 fractions, according to the study protocol.

Other Names:
  • IMNI Group
Active Comparator: Non-IMNI Group

Participants will receive adjuvant radiotherapy to the breast or chest wall and regional lymph nodes without irradiation of the internal mammary lymph nodes.
Radiation: Locoregional Radiotherapy Without Internal Mammary Node Irradiation

Adjuvant locoregional radiotherapy to the breast or chest wall and regional lymph nodes, with intentional omission of the internal mammary lymph nodes. Allowed dose-fractionation schedules include 50 Gy in 25 fractions, 42.5 Gy in 16 fractions, or 40 Gy in 15 fractions, according to the study protocol.

Other Names:
  • Non-IMNI Group

What is the study measuring?

Primary Outcome Measures

Primary Outcome Measures

In a clinical study's protocol, the planned outcome measure that is the most important for evaluating the effect of an intervention/treatment. Most clinical studies have one primary outcome measure, but some have more than one.
Outcome Measure
Measure Description
Time Frame
Disease-Free Survival (DFS)
Time Frame: From randomization through 5 years

Disease-free survival is defined as the time from randomization to the first occurrence of locoregional recurrence, distant metastasis, or death from any cause, whichever occurs first.
From randomization through 5 years

Secondary Outcome Measures

Secondary Outcome Measures

In a clinical study's protocol, a planned outcome measure that is not as important as the primary outcome measure for evaluating the effect of an intervention but is still of interest. Most clinical studies have more than one secondary outcome measure.
Outcome Measure
Measure Description
Time Frame
Overall Survival (OS)
Time Frame: Up to 5 years after randomization

Overall survival is defined as the time from randomization to death from any cause.
Up to 5 years after randomization
Breast Cancer Mortality
Time Frame: Up to 5 years after randomization

Breast cancer mortality is defined as the time from randomization to death attributable to breast cancer.
Up to 5 years after randomization
Locoregional Recurrence-Free Survival (LRFS)
Time Frame: Up to 5 years after randomization

Locoregional recurrence-free survival is defined as the time from randomization to the occurrence of locoregional recurrence.
Up to 5 years after randomization
Distant Metastasis-Free Survival (DMFS)
Time Frame: Up to 5 years after randomization

Distant metastasis-free survival is defined as the time from randomization to the occurrence of distant metastasis.
Up to 5 years after randomization
Incidence and Severity of Cardiac Toxicity Assessed Using RTOG/EORTC Radiation Morbidity Scoring Criteria
Time Frame: Last week of radiotherapy, then at 1, 3, and 6 months, and every 6 months through 2 years

Acute cardiac toxicity will be assessed using the RTOG Acute Radiation Morbidity Scoring Criteria, while late cardiac toxicity will be assessed using the RTOG/EORTC Late Radiation Morbidity Scoring Schema. Toxicity will be graded from 0 (no toxicity) to 5 (death related to toxicity). The incidence and severity of cardiac toxicity will be compared between treatment groups.
Last week of radiotherapy, then at 1, 3, and 6 months, and every 6 months through 2 years
Incidence and Severity of Pulmonary Toxicity Assessed Using RTOG/EORTC Radiation Morbidity Scoring Criteria
Time Frame: Last week of radiotherapy, then at 1, 3, and 6 months, and every 6 months through 2 years

Acute pulmonary toxicity will be assessed using the RTOG Acute Radiation Morbidity Scoring Criteria, while late pulmonary toxicity will be assessed using the RTOG/EORTC Late Radiation Morbidity Scoring Schema. Toxicity will be graded from 0 (no toxicity) to 5 (death related to toxicity). The incidence and severity of pulmonary toxicity will be compared between the two treatment groups.
Last week of radiotherapy, then at 1, 3, and 6 months, and every 6 months through 2 years

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Sponsor

The organization or person who initiates the study and who has authority and control over the study.
Mahidol University

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Estimated)

Study Start

The actual date on which the first participant was enrolled in a clinical study. The "anticipated" study start date is the date that the researchers think will be the study start date.
July 1, 2027

Primary Completion (Estimated)

Primary Completion

The date on which the last participant in a clinical study was examined or received an intervention to collect final data for the primary outcome measure. Whether the clinical study ended according to the protocol or was terminated does not affect this date. For clinical studies with more than one primary outcome measure with different completion dates, this term refers to the date on which data collection is completed for all the primary outcome measures. The "anticipated" primary completion date is the date that the researchers think will be the primary completion date for the study.
July 1, 2032

Study Completion (Estimated)

Study Completion

The date on which the last participant in a clinical study was examined or received an intervention/treatment to collect final data for the primary outcome measures, secondary outcome measures, and adverse events (that is, the last participant's last visit). The "anticipated" study completion date is the date that the researchers think will be the study completion date.
July 1, 2036

Study Registration Dates

First Submitted

First Submitted

The date on which the study sponsor or investigator first submitted a study record to ClinicalTrials.gov. There is typically a delay of a few days between the first submitted date and the record's availability on ClinicalTrials.gov (the first posted date).
October 28, 2026

First Submitted That Met QC Criteria

First Submitted That Met QC Criteria

The date on which the study sponsor or investigator first submits a study record that is consistent with National Library of Medicine (NLM) quality control (QC) review criteria. The sponsor or investigator may need to revise and submit a study record one or more times before NLM's QC review criteria are met. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 3, 2026

First Posted (Actual)

First Posted

The date on which the study record was first available on ClinicalTrials.gov after National Library of Medicine (NLM) quality control (QC) review has concluded. There is typically a delay of a few days between the date the study sponsor or investigator submitted the study record and the first posted date.
November 4, 2026

Study Record Updates

Last Update Posted (Actual)

Last Update Posted

The most recent date on which changes to a study record were made available on ClinicalTrials.gov. There may be a delay between when the changes were submitted to ClinicalTrials.gov by the study's sponsor or investigator (the last update submitted date) and the last update posted date.
November 4, 2026

Last Update Submitted That Met QC Criteria

Last Update Submitted That Met QC Criteria

The most recent date on which the study sponsor or investigator submitted changes to a study record that are consistent with National Library of Medicine (NLM) quality control (QC) review criteria. It is the responsibility of the sponsor or investigator to ensure that the study record is consistent with the NLM QC review criteria.
November 3, 2026

Last Verified

Last Verified

The most recent date on which the study sponsor or investigator confirmed the information about a clinical study on ClinicalTrials.gov as accurate and current. If a study with a recruitment status of recruiting; not yet recruiting; or active, not recruiting has not been confirmed within the past 2 years, the study's recruitment status is shown as unknown.
October 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

Other Study ID Numbers

Identifiers or ID numbers other than the NCT number that are assigned to a clinical study by the study's sponsor, funders, or others. These numbers may include unique identifiers from other trial registries and National Institutes of Health grant numbers.
  • 587/2569(IRB2)

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

No

Studies a U.S. FDA-regulated device product

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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