PRIME II
PRIME II confirmed in a larger and more recent population that omitting radiotherapy in older women with low-risk hormone-sensitive breast cancer raises local recurrence modestly without affecting survival.
Overview
PRIME II randomised 1,326 women aged 65 or older with hormone receptor-positive, node-negative breast cancers up to 3 cm, treated by breast-conserving surgery and endocrine therapy, to radiotherapy or none. Ten-year local recurrence was 9.5 percent without radiotherapy and 0.9 percent with it; distant recurrence, breast cancer-specific and overall survival did not differ (Kunkler and colleagues, Lancet Oncology 2015 and New England Journal of Medicine 2023).
- 9.5 vs 0.9 out of 100 reached this endpoint at 10 years with Endocrine therapy alone compared with Endocrine therapy plus radiotherapy; 8.6 more per 100.
- Roughly one extra person helped for every 12 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: Women aged 65 or over with low-risk hormone receptor-positive breast cancer after breast-conserving surgery: endocrine therapy with or without whole-breast radiotherapy. 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.
1,326 participants enrolled.
| Endpoint | Arm | n | Value | HR (95% CI) | p | Source |
|---|---|---|---|---|---|---|
| Ipsilateral breast tumour recurrence at 10 yearsprimary | Endocrine therapy alone | 668 | 9.5% | - | - | - |
| Endocrine therapy plus radiotherapy | 658 | 0.9% |
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