A Phase 3 interventional study of Locoregional Radiotherapy With Internal Mammary Node Irradiation and Locoregional Radiotherapy Without Internal Mammary Node Irradiation in Breast Neoplasms, sponsored by Mahidol University. Not yet recruiting at 9 sites in Thailand. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-11-04.
Sponsored by Mahidol University · Phase 3, Interventional, and Treatment
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.
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.
14,825 studies on the registry are indexed under Breast Neoplasms; 3,319 are open to participants now.
This study's planned enrollment of 1,760 is above the median of 72 across 10,896 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Mahidol University is the lead sponsor of 747 studies on the registry; 119 are open to participants now.
Counted across the registry records on this site, refreshed daily.
Go through the criteria one by one — yes, no or not sure — and take the list to your doctor or the study team. Kept in this browser only.
Exclusion Criteria:
Underlined terms in the criteria open these too. Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Histologically or cytologically confirmed
The diagnosis was confirmed by looking at a sample under a microscope: tissue from a biopsy or surgery (histology), or cells from a fluid or needle sample (cytology).
Your pathology report is the document that shows this.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Adjuvant and neoadjuvant
Neoadjuvant treatment is given before the main treatment (usually surgery), often to shrink a tumour. Adjuvant treatment is given after it, to lower the chance of the cancer coming back.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Cancer (malignancy)
Malignancy means cancer. Criteria about another or earlier malignancy ask whether you have had a different cancer, usually within a set number of years.
Some are commonly allowed, such as treated skin cancers other than melanoma and early cancers removed completely — check the exceptions this study lists.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Metastases
Cancer that has spread from where it began to other parts of the body. “Metastatic” cancer is cancer that has spread this way.
Explained by clinicaltrials.gg, not part of the registry record. The study team decides who can take part.
Participants will receive adjuvant locoregional radiotherapy including irradiation of the internal mammary lymph nodes.
Radiation: Locoregional Radiotherapy With Internal Mammary Node Irradiation
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, 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.
Also known as: IMNI Group
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.
Also known as: Non-IMNI Group
Disease-Free Survival (DFS)
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.
Time frame: From randomization through 5 years
Overall Survival (OS)
Overall survival is defined as the time from randomization to death from any cause.
Time frame: Up to 5 years after randomization
Breast Cancer Mortality
Breast cancer mortality is defined as the time from randomization to death attributable to breast cancer.
Time frame: Up to 5 years after randomization
Locoregional Recurrence-Free Survival (LRFS)
Locoregional recurrence-free survival is defined as the time from randomization to the occurrence of locoregional recurrence.
Time frame: Up to 5 years after randomization
Distant Metastasis-Free Survival (DMFS)
Distant metastasis-free survival is defined as the time from randomization to the occurrence of distant metastasis.
Time frame: Up to 5 years after randomization
Incidence and Severity of Cardiac Toxicity Assessed Using RTOG/EORTC Radiation Morbidity Scoring Criteria
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.
Time frame: 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
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.
Time frame: Last week of radiotherapy, then at 1, 3, and 6 months, and every 6 months through 2 years
Plan to share: No
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
This study is not yet recruiting, as verified in Oct 2026. You cannot join it, but the record below documents what was studied.
Get an email when the registry record changes — status, dates, results — or when someone posts here.
Sign in to followQuestions and observations about this study, from anyone following it. Not medical advice, and not a channel to the study team — their contact details are on the registry record.
Sign in to join the discussion. Reading takes no account; posting does. You choose a display name, and a pseudonym is the default.
Nothing here yet. If you are running this trial, taking part in it, or weighing whether to, this is the place to say so.