The Absolute Effect / Evidence / PRIME II
Breast Cancer · Radiation Oncology · RT Omission
PRIME II
Clinical question
In older women with low-risk HR-positive node-negative breast cancer, what is the absolute benefit of adjuvant breast RT?
Trial context
Population
1,326 women ≥65 years with low-risk HR-positive node-negative breast cancer
Intervention
Whole-breast RT vs no RT after BCS + endocrine therapy
Key endpoint
10-year local recurrence
Time horizon / follow-up
10 years
Absolute Effect
What changes for patients?
10-year local recurrence was 0.9% with RT versus 9.5% without RT, an absolute reduction of 8.6 percentage points (NNT 12). Overall survival was essentially identical, 80.7% vs 80.8%. NNT is based on 10-year local recurrence.
NNT: 12
Treatment burden / harm
Additional RT toxicity
NNH: Not quantifiable from the trial's main reported toxicity data
Relative effect
HR: 10.4 for no RT vs RT
95% CI 4.1–26.1
Clinical interpretation
PRIME II shows that omitting RT in carefully selected older women on endocrine therapy increases local recurrence without changing overall survival at 10 years.
Primary publication
- Kunkler IH, et al. N Engl J Med. 2023;388:585–594.
- Primary publication / source