NSABP B-39/RTOG 0413
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.
Overview
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).
- 4.6 vs 3.9 out of 100 reached this endpoint at 10 years with Accelerated partial-breast irradiation compared with Whole-breast irradiation; 0.7 more per 100.
- Roughly one extra person helped for every 143 treated. That is a rough figure taken from the two percentages, not a guarantee for any one person.
- This endpoint is not one of the standard survival or response measures; read it alongside the trial's primary result.
- These results apply to the people the trial enrolled: Early breast cancer or DCIS after lumpectomy: accelerated partial-breast irradiation (twice daily over one week) versus whole-breast irradiation. People in a different situation may not see the same effect.
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 participants 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% |
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