Home › Trials › NCT05417516

Comparing two types of breast radiation therapy after surgery

A Randomized Trial of Five-Fraction Partial Breast Irradiation (RAPID2)

Phase 3 Interventional Ontario Clinical Oncology Group (OCOG) · NCT05417516

This study is testing whether partial breast radiation or whole breast radiation works better for women with small, node-negative breast cancer after surgery.

Quick facts

PhasePhase 3
Study typeInterventional
Enrollment910 (estimated)
Ages50 Years to 120 Years
SexFemale
SponsorOntario Clinical Oncology Group (OCOG) Academic / other
Drugs / interventionschemotherapy, radiation
Locations28 sites (Darlinghurst, New South Wales and 27 other locations)
Trial IDNCT05417516 on ClinicalTrials.gov

What this trial studies

This clinical trial aims to compare the effectiveness of Partial Breast Irradiation (PBI) versus Whole Breast Irradiation (WBI) in women with node-negative breast cancer that is 3 cm or smaller. Participants will be randomly assigned to receive either treatment after undergoing breast-conserving surgery. The study will assess local recurrence rates and patient-reported cosmetic outcomes three years after treatment. The trial is designed to ensure that participants are unaware of their treatment allocation to minimize bias in their assessments.

Who should consider this trial

Good fit: Ideal candidates are women aged 50 and older with newly diagnosed invasive breast cancer, measuring 3 cm or smaller, and with clear surgical margins.

Not a fit: Patients under 50 years old or those with BRCA mutations will not benefit from this study.

Why it matters

Potential benefit: If successful, this study could provide a less invasive radiation option that maintains cosmetic outcomes for breast cancer patients.

How similar studies have performed: Previous studies have shown promising results with partial breast irradiation, indicating potential for success in this approach.

Eligibility criteria

Show full inclusion / exclusion criteria 
Inclusion Criteria:

For inclusion in this study, patients must fulfill all of the following criteria:

1. Female with a new histological diagnosis of invasive carcinoma of the breast with no evidence of metastatic disease (see AJCC TNM Cancer Staging, Appendix II).
2. Treated by BCS with microscopically clear resection margins \>= 1mm for invasive and non-invasive disease or no residual disease on re-excision.
3. Negative axillary node involvement as determined by either sentinel lymph node biopsy or axillary node dissection or clinical assessment with a negative axillary ultrasound and/or biopsy, for women with unifocal tumours \<= 2cm, histologic grade 1 or 2, ER or PR+ and HER2-ve that are being planned for endocrine therapy

Exclusion Criteria:

Patients who satisfy any of the following exclusion criteria are NOT eligible for this study:

1. Age less than 50 years.
2. Known to be BRCA 1 and/or BRCA 2 positive.
3. Tumour size \>3cm in greatest diameter on pathological examination.
4. Evidence of extensive intraductal component (EIC) (defined as an invasive tumour with a ductal carcinoma in situ (DCIS) component comprising at least 25% and extending beyond the invasive component to surrounding normal breast tissue) with the following exception: smaller tumours with EIC where the combined size (of the invasive and DCIS components) are \<= 3cm remain eligible
5. Evidence of a DCIS component \> 3cm
6. Lobular carcinoma only.
7. More than one primary tumour in different quadrants of the same breast (patients with multifocal breast cancer are eligible).
8. Synchronous or previous contralateral breast cancer (patients with contralateral DCIS or LCIS are eligible).
9. History of non-breast malignancy within the last 5 years other than treated non-melanoma skin cancer or treated in-situ carcinoma.
10. Known pregnancy or currently lactating.
11. Inability to localize tumour bed on CT planning (no evidence of surgical clips or seroma).
12. Inability to plan the patient for the experimental technique.

Where this trial is running

Darlinghurst, New South Wales and 27 other locations

Study contacts

How to participate

  1. Review the eligibility criteria above with your treating physician.
  2. Visit the official trial page on ClinicalTrials.gov for the most current contact information and recruitment status.
  3. Contact the listed study coordinator or principal investigator to request pre-screening. Pre-screening is free and never obligates you to enroll.
View on ClinicalTrials.gov → Find more trials like this →
Conditions Breast Neoplasm FemaleRadiotherapyCosmetic Outcome
Last reviewed 2026-06-13 by the Find a Trial editorial team. Information on this page is for educational purposes and is not medical advice. Always consult qualified healthcare professionals about clinical trial participation.