Breast CancerPhase 3APROOBNCT07757958
Partial Breast Irradiation Without Sentinel Lymph Node Biopsy in Low-Risk Early Breast Cancer
A Phase 3 study testing Whole Breast Irradiation and Partial Breast Irradiation in people with Breast Cancer and Node-negative Breast Cancer, run by Samsung Medical Center at 1 site in South Korea.
Trial summary
This is a multicenter, randomized, phase III non-inferiority trial in women aged 40 years or older with clinically node-negative (cN0), pathologically pT1 (≤2 cm), grade 1-2, lymphovascular invasion (LVI)-negative invasive breast cancer treated with breast-conserving surgery (BCS) in whom sentinel lymph node biopsy… Read more about this study
- Who is it for?
- Ages 40 years and older, women only
- Conditions the study is for
- Breast Cancer, Node-negative Breast Cancer, Early-Stage Invasive Breast Carcinoma
- What is being tested?
- Whole Breast Irradiation and Partial Breast Irradiation
- Type of treatment
- Surgery or procedure
- Could I receive a placebo?
- No, everyone receives an active treatment
- How many people
- 520 participants
- Where
- 1 siteSouth Korea
- Study dates
- 1 Aug 2026to Jun 2036
- Phase
- Phase 3
- Are there results?
- Not yet: the study is under way
Key requirements
Who can take part, as listed by the sponsor. Only the study team can confirm whether you are eligible, so take this list to your doctor.
- Ages 40 years and older
- Women only
- No healthy volunteers
- Adult, Older adult
Who may be able to join
- Female ≥40 years with histologically confirmed unilateral invasive breast cancer.
- No suspicious nodal metastasis on preoperative axillary ultrasound (cN0).
- Single lesion in the affected breast on preoperative breast ultrasound and mammography.
- Treated with breast-conserving surgery with pathologically negative margins for the invasive tumor.
- Sentinel lymph node biopsy not performed at surgery (pNx).
- Maximum diameter of invasive tumor ≤2 cm on final pathology (pT1).
- Histologic grade 1 or 2.
- Signed informed consent prior to enrollment.
Who cannot join
- History of malignancy other than breast cancer within 5 years (except adequately treated non-melanoma skin cancer, or carcinoma in situ excluding breast carcinoma in situ).
- Preoperative diagnosis of carcinoma in situ without axillary nodal sampling, subsequently diagnosed as invasive breast cancer on final pathology with SLNB omitted.
- Lymphovascular invasion present (LVI+).
- Multifocal or multicentric tumor in the same breast confirmed radiologically or pathologically.
- Bilateral or inflammatory breast cancer.
- Prior radiotherapy to the breast or thorax.
- Confirmed pathogenic or likely pathogenic variant in a hereditary breast cancer gene (including BRCA1/2).
- Recurrent breast cancer.
Trial locations and contacts
1 site in 1 country. Contact the study team or a site near you to ask about taking part.
South Korea1 site
Samsung Medical Center
Seoul, 05649
Haeyoung Kim, +82234102612, haeyoung0131.kim@samsung.com
Wonkyung Cho, wklove.cho@gmail.com
About this study
Official title: A Phase III Randomized Trial of Partial Versus Whole Breast Radiotherapy in Clinically Node-Negative Early Breast Cancer Omitting Sentinel Lymph Node Biopsy (APROOB Trial)
This is a multicenter, randomized, phase III non-inferiority trial in women aged 40 years or older with clinically node-negative (cN0), pathologically pT1 (≤2 cm), grade 1-2, lymphovascular invasion (LVI)-negative invasive breast cancer treated with breast-conserving surgery (BCS) in whom sentinel lymph node biopsy (SLNB) was omitted (pNx). Eligible patients are randomized 1:1 to partial breast irradiation (PBI) or whole breast irradiation (WBI). The primary aim is to determine whether PBI is non-inferior to WBI with respect to the 5-year recurrence-free survival (RFS) rate. Secondary aims include comparison of axillary recurrence, overall survival, locoregional recurrence, treatment-related toxicity, and quality of life between arms.
Read the detailed description
Background and rationale. PBI has shown oncologic outcomes comparable to WBI in low-risk early breast cancer in several randomized trials (e.g., IMPORT LOW, RAPID, GEC-ESTRO, Florence). Separately, SLNB omission has demonstrated oncologic safety in clinically node-negative patients (e.g., SOUND, INSEMA, BOOG). However, the long-term oncologic safety of combining SLNB omission with PBI has not been established. Because pathologic nodal status is unknown in SLNB-omitted patients, occult nodal micrometastasis cannot be fully excluded despite cN0 status, and the reduced treatment volume of PBI relative to WBI may theoretically increase the risk of axillary or regional nodal recurrence. The strict eligibility criteria (negative axillary ultrasound, pT1, grade 1-2, LVI-negative, single lesion, negative margins) are intended to limit the absolute magnitude of this residual risk.
Design. Eligible, consented patients are centrally randomized 1:1 to WBI or PBI, with block randomization stratified by age (<50 vs ≥50 years), tumor size (≤1 cm vs >1 cm), and hormone receptor status (HR+/HER2- vs other).
Quality assurance. For the first 3 patients enrolled at each participating institution, central review is performed on CT simulation images, CTV/PTV/OAR contours, axillary level I-III contours, treatment plans with dose-volume histograms (DVH), and dose/fractionation data. Central review verifies ESTRO-consistent target definition, OAR contouring adequacy, protocol-compliant dose prescription, PTV coverage and OAR dose constraints, axillary level I-III dosimetry, and confirms that high-tangent technique or regional nodal irradiation (RNI) is not used.
Follow-up schedule. V1 (end of RT); V2 (3 weeks post-RT); V3 (6 months); V4 (12 months); V5 (annually, years 2-4); V6 (5 years). Annual mammography and breast ultrasound are performed; additional imaging is performed if recurrence is suspected. Extended follow-up to 10 years is planned for long-term oncologic safety and late toxicity (breast cancer-specific survival, overall survival, late locoregional recurrence, late radiation toxicity)
- Being tested
- Whole Breast Irradiation, Partial Breast Irradiation
- Keywords
- Partial breast irradiation, Whole breast irradiation, Breast-conserving surgery, Sentinel lymph node biopsy omission, Node-negative, Radiotherapy de-escalation
- Medical subject headings
- Breast Neoplasms
What participants receive
What participants receive. In a randomised study each person is assigned to one group by chance.
Whole Breast IrradiationRadiation
Total dose 26-45 Gy in 5-20 fractions; each institution applies a pre-selected fractionation schedule consistently.
CTV defined per ESTRO guideline to include the whole breast parenchyma; PTV with institutional set-up margin (e.g., 5-7 mm).
Tumor bed boost (sequential 10-16 Gy in 4-8 fractions, or simultaneous integrated boost [SIB]) per institutional standard.
Regional nodal irradiation and high-tangent technique not permitted; axillary levels I-III contoured for dosimetric analysis only.
Partial Breast IrradiationRadiation
Total dose 30-40 Gy in 5-15 fractions. Recommended schedules: 30 Gy in 5 fractions (once daily [QD] or twice daily [BID]); or 40.05 Gy in 15 fractions (QD over ~3 weeks).
Axillary levels I-III contoured for incidental dosimetric analysis only (not a treatment target).
| Study group | Role | What they receive |
|---|---|---|
| Whole Breast Irradiation (WBI) | Active comparator | Whole breast irradiation using 3D conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT). Receives: Radiation: Whole Breast Irradiation |
| Partial Breast Irradiation (PBI) | Experimental | Partial breast irradiation targeting the tumor bed with margin, using 3D-CRT or IMRT, sparing the remainder of the breast. Receives: Radiation: Partial Breast Irradiation |
What is being measured
The primary outcome is the main question the study is designed to answer.
5-Year Recurrence-Free Survival Rate
Proportion of patients free from a first RFS event at 5 years. An RFS event is defined as the first occurrence of ipsilateral invasive breast recurrence, ipsilateral regional nodal recurrence (including axillary), distant metastasis, or breast cancer death. Measured from date of randomization to first event.
Measured: 5 years from randomization
Secondary outcomes (3)
5-Year Axillary Recurrence Rate
Incidence of axillary nodal recurrence.
Measured: 5 years from randomization
5-year locoregional recurrence rate
Incidence of ipsilateral breast or ipsilateral regional (axillary, supraclavicular or IMN) recurrence.
Measured: 5 years from randomization
5-Year Overall Survival
survival from randomization to death from any cause
Measured: 5 years from randomization.
Timeline
From the start of the study to its completion; the mark is today. Estimated dates are the sponsor’s plan.
- First posted11 Aug 2026
- Study start1 Aug 2026 (estimated)
- Primary completionJun 2036 (estimated)
- Study completionJun 2036 (estimated)
Resources
- Official record on ClinicalTrials.govThe registry entry this page is built from, with its full change history.
- Other trials for Breast CancerStudies of the same condition, open and under way.
- More trials run by Samsung Medical CenterThe sponsor's other registered studies.
- What the trial phases meanHow a treatment moves from first tests in people to approval.
More details
For doctors and researchers: how the study is designed, who runs it, and its registry IDs.
Study design
- Study type
- Interventional
- Phase
- Phase 3
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Model description
- 1:1 randomization to PBI or WBI; non-inferiority design
- Masking
- None (open label)
- Enrolment
- 520 participants (estimated)
Sponsor and investigators
- Lead sponsor
- Samsung Medical Center
- Sponsor type
- University, hospital or other
- Collaborators
- National Institute of Health, Korea
- Responsible party
- Principal investigator, Haeyoung Kim, Samsung Medical Center
IDs, dates and publications
- ClinicalTrials.gov ID
- NCT07757958
- Sponsor's protocol ID
- 2026-04-070-001
- Acronym
- APROOB
- Status last verified
- Aug 2026
- First submitted
- 6 Aug 2026
- Last updated
- 11 Aug 2026
- Results posted
- No
- Data monitoring committee
- Yes
- FDA-regulated drug
- No
- FDA-regulated device
- No
- Individual data sharing
- Undecided
Study at a glance
From the registry record, last updated by the sponsor on 11 Aug 2026. Recruitment status is as the sponsor reported it: confirm with the study team.
- Official title
- A Phase III Randomized Trial of Partial Versus Whole Breast Radiotherapy in Clinically Node-Negative Early Breast Cancer Omitting Sentinel Lymph Node Biopsy (APROOB Trial)
- ClinicalTrials.gov ID
- NCT07757958
- Acronym / sponsor ID
- APROOB / 2026-04-070-001
- Keywords
- Partial breast irradiation, Whole breast irradiation, Breast-conserving surgery, Sentinel lymph node biopsy omission, Node-negative, Radiotherapy de-escalation
- Phase
- Phase 3
- Study type
- Interventional
- Recruitment status
- Not yet recruiting
- Enrolment
- 520 participants (estimated)
- Lead sponsor
- Samsung Medical CenterUniversity, hospital or other
- Collaborators
- National Institute of Health, Korea
- Study start
- 1 Aug 2026 (estimated)
- Primary completion
- Jun 2036 (estimated)
- Study completion
- Jun 2036 (estimated)
- First posted
- 11 Aug 2026 (actual)
- Results
- Not posted in the source record
Clinical summary
The research question as the sponsor registered it. This describes what the study plans to test, not what it found.
This is a multicenter, randomized, phase III non-inferiority trial in women aged 40 years or older with clinically node-negative (cN0), pathologically pT1 (≤2 cm), grade 1-2, lymphovascular invasion (LVI)-negative invasive breast cancer treated with breast-conserving surgery (BCS) in whom sentinel lymph node biopsy (SLNB) was omitted (pNx). Eligible patients are randomized 1:1 to partial breast irradiation (PBI) or whole breast irradiation (WBI). The primary aim is to determine whether PBI is non-inferior to WBI with respect to the 5-year recurrence-free survival (RFS) rate. Secondary aims include comparison of axillary recurrence, overall survival, locoregional recurrence, treatment-related toxicity, and quality of life between arms.
Detailed description
Background and rationale. PBI has shown oncologic outcomes comparable to WBI in low-risk early breast cancer in several randomized trials (e.g., IMPORT LOW, RAPID, GEC-ESTRO, Florence). Separately, SLNB omission has demonstrated oncologic safety in clinically node-negative patients (e.g., SOUND, INSEMA, BOOG). However, the long-term oncologic safety of combining SLNB omission with PBI has not been established. Because pathologic nodal status is unknown in SLNB-omitted patients, occult nodal micrometastasis cannot be fully excluded despite cN0 status, and the reduced treatment volume of PBI relative to WBI may theoretically increase the risk of axillary or regional nodal recurrence. The strict eligibility criteria (negative axillary ultrasound, pT1, grade 1-2, LVI-negative, single lesion, negative margins) are intended to limit the absolute magnitude of this residual risk.
Design. Eligible, consented patients are centrally randomized 1:1 to WBI or PBI, with block randomization stratified by age (<50 vs ≥50 years), tumor size (≤1 cm vs >1 cm), and hormone receptor status (HR+/HER2- vs other).
Quality assurance. For the first 3 patients enrolled at each participating institution, central review is performed on CT simulation images, CTV/PTV/OAR contours, axillary level I-III contours, treatment plans with dose-volume histograms (DVH), and dose/fractionation data. Central review verifies ESTRO-consistent target definition, OAR contouring adequacy, protocol-compliant dose prescription, PTV coverage and OAR dose constraints, axillary level I-III dosimetry, and confirms that high-tangent technique or regional nodal irradiation (RNI) is not used.
Follow-up schedule. V1 (end of RT); V2 (3 weeks post-RT); V3 (6 months); V4 (12 months); V5 (annually, years 2-4); V6 (5 years). Annual mammography and breast ultrasound are performed; additional imaging is performed if recurrence is suspected. Extended follow-up to 10 years is planned for long-term oncologic safety and late toxicity (breast cancer-specific survival, overall survival, late locoregional recurrence, late radiation toxicity)
Study design
- Primary purpose
- Treatment
- Allocation
- Randomised
- Intervention model
- Parallel groups
- Masking
- None (open label)
- Number of arms
- 2
- Model description
- 1:1 randomization to PBI or WBI; non-inferiority design
| Arm | Type | Receives |
|---|---|---|
| Whole Breast Irradiation (WBI) | Active comparator | Radiation: Whole Breast IrradiationWhole breast irradiation using 3D conformal radiotherapy (3D-CRT) or intensity-modulated radiotherapy (IMRT). |
| Partial Breast Irradiation (PBI) | Experimental | Radiation: Partial Breast IrradiationPartial breast irradiation targeting the tumor bed with margin, using 3D-CRT or IMRT, sparing the remainder of the breast. |
Who may qualify
- Ages
- 40 years and older
- Sex
- Female only
- Healthy volunteers
- Not accepted
- Age groups
- Adult, Older adult
Key inclusion criteria (8 listed)
- Female ≥40 years with histologically confirmed unilateral invasive breast cancer.
- No suspicious nodal metastasis on preoperative axillary ultrasound (cN0).
- Single lesion in the affected breast on preoperative breast ultrasound and mammography.
- Treated with breast-conserving surgery with pathologically negative margins for the invasive tumor.
- Sentinel lymph node biopsy not performed at surgery (pNx).
Key exclusion criteria (8 listed)
- History of malignancy other than breast cancer within 5 years (except adequately treated non-melanoma skin cancer, or carcinoma in situ excluding breast carcinoma in situ).
- Preoperative diagnosis of carcinoma in situ without axillary nodal sampling, subsequently diagnosed as invasive breast cancer on final pathology with SLNB omitted.
- Lymphovascular invasion present (LVI+).
- Multifocal or multicentric tumor in the same breast confirmed radiologically or pathologically.
- Bilateral or inflammatory breast cancer.
Eligibility is decided by the study team after screening; this overview does not establish that a patient qualifies. Full inclusion and exclusion criteria.
Interventions
| Intervention | Type | Arms |
|---|---|---|
| Whole Breast IrradiationTotal dose 26-45 Gy in 5-20 fractions; each institution applies a pre-selected fractionation schedule consistently. CTV defined per ESTRO guideline to include the whole breast parenchyma; PTV with institutional set-up margin (e.g., 5-7 mm). Tumor bed boost (sequential 10-16 Gy in 4-8 fractions, or simultaneous integrated boost [SIB]) per institutional standard. Regional nodal irradiation and high-tangent technique not permitted; axillary levels I-III contoured for dosimetric analysis only. | Radiation | Whole Breast Irradiation (WBI) |
| Partial Breast IrradiationTotal dose 30-40 Gy in 5-15 fractions. Recommended schedules: 30 Gy in 5 fractions (once daily [QD] or twice daily [BID]); or 40.05 Gy in 15 fractions (QD over ~3 weeks). Axillary levels I-III contoured for incidental dosimetric analysis only (not a treatment target). | Radiation | Partial Breast Irradiation (PBI) |
Primary outcome
5-Year Recurrence-Free Survival Rate
Time frame: 5 years from randomization
Proportion of patients free from a first RFS event at 5 years. An RFS event is defined as the first occurrence of ipsilateral invasive breast recurrence, ipsilateral regional nodal recurrence (including axillary), distant metastasis, or breast cancer death. Measured from date of randomization to first event.
3 secondary outcomes
5-Year Axillary Recurrence Rate
Time frame: 5 years from randomization
5-year locoregional recurrence rate
Time frame: 5 years from randomization
5-Year Overall Survival
Time frame: 5 years from randomization.
Results and safety
This study is still under way. Results are not available in the source record yet.
Research links
- Official record on ClinicalTrials.govLast updated by the sponsor 11 Aug 2026.
- Individual participant dataSharing planned: Undecided
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Referral and contact
AzTrials does not enrol participants or take referrals. Contact the study team or a site listed below; they decide who can take part.
1 site in 1 country: see every site and its status.
Questions about this trial
What is this clinical trial studying?
A Phase 3 study testing Whole Breast Irradiation and Partial Breast Irradiation in people with Breast Cancer and Node-negative Breast Cancer, run by Samsung Medical Center at 1 site in South Korea.
The full registered description is in the About this study section and the official record.
Who may be eligible to take part?
The sponsor lists 8 inclusion and 8 exclusion criteria. Eligibility is decided by the study team after screening, so read the full criteria and contact a listed site.
Is this clinical trial currently recruiting?
The record says: opening soon, as of the sponsor's last update on 11 Aug 2026. Status can change between updates, so confirm with the study contact before making plans.
Where is the study taking place?
The record lists 1 site in South Korea. Whether a site is taking part right now should be confirmed with that site. See every site.
What are the possible benefits and risks?
They depend on the study and the treatment, and no study can promise a benefit. The study team explains the known risks during informed consent, before anyone joins; the record itself does not list them.
What does this phase mean?
Phase 3 studies compare the treatment with the current standard treatment or a placebo in a large group, to confirm how well it works and watch for side effects.
Not every study follows the same path, and some studies (observational studies, device studies) have no phase.
Are results available for this study?
This study is still under way. Results are not available in the source record yet.
How can a doctor refer a patient or contact the research team?
Contact Haeyoung Kim (+82234102612, haeyoung0131.kim@samsung.com), or a site near the patient. AzTrials does not enrol participants or take referrals.
What does the primary outcome measure?
5-Year Recurrence-Free Survival Rate (time frame: 5 years from randomization). It is what the study was designed to measure, not a finding.
Where can I read the original study information?
Does a listing mean the treatment is approved or proven to work?
No. A listing means the study is registered. It does not show that the treatment is safe, works, or is approved by a regulator.
How often is this information updated?
AzTrials copies changed records from ClinicalTrials.gov every night and reloads the whole registry every week. The sponsor last updated this record on 11 Aug 2026.