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The largest partial-breast trial found recurrence rates within one percentage point of whole-breast treatment but could not formally prove equivalence, so accelerated partial-breast irradiation is offered to selected lower-risk women rather than everyone.
NSABP B-39/RTOG 0413 randomised 4,216 women with stage 0 to II breast cancer to whole-breast irradiation or accelerated partial-breast irradiation given twice daily over five to ten days by brachytherapy or external beam. Ten-year ipsilateral breast tumour recurrence was 4.6 percent with partial-breast and 3.9 percent with whole-breast treatment; the hazard ratio's confidence interval crossed the equivalence margin, so equivalence was not established, although the absolute difference was small (Vicini and colleagues, Lancet 2019).
Numbers are from the trial as recorded here; see the source links in the table below. This is orientation, not medical advice: ask your team how closely the trial population matches you.
4,216 enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Ipsilateral breast tumour recurrence at 10 yearsprimary | Accelerated partial-breast irradiation | 2,107 | 4.6% | - | - | - |
| Whole-breast irradiation | 2,109 | 3.9% |
The full inclusion and exclusion criteria are on the registry record. Read 2026-10-07. Recruiting overall does not mean a particular site is open; ask the study team.
ClinicalTrials.gov data courtesy of the US National Library of Medicine.
Shares RAPID (accelerated partial-breast irradiation), TARGIT-A (targeted intraoperative radiotherapy), Partial-breast irradiation, HER2-positive breast cancer and the tag radiation-wave2.
Shares Partial-breast irradiation, HER2-positive breast cancer, IMRT / IGRT (modern external beam), Breast cancer (all types) and the tag radiation-wave2.
Shares Partial-breast irradiation, HER2-positive breast cancer, IMRT / IGRT (modern external beam), Breast cancer (all types) and the tag radiation-wave2.
Shares IMRT / IGRT (modern external beam), Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag radiation-wave2.
Shares IMRT / IGRT (modern external beam), Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag radiation-wave2.
Shares NRG Oncology, IMRT / IGRT (modern external beam) and the tag radiation-wave2.
Shares NRG Oncology, IMRT / IGRT (modern external beam) and the tag radiation-wave2.
Shares Breast cancer (all types), HR-positive / HER2-negative breast cancer and the tag radiation-wave2.
Every source this page cites, grouped by who published it. Grouping is read from the web address, not assigned by hand.
A source that has moved or gone is reported by the weekly link check. /audit/