- Accelerated partial breast irradiation (PBI) after lumpectomy is marginally less effective than whole-breast irradiation (WBI) for preventing ipsilateral breast tumor recurrence (IBTR), according to data from the phase 3 NSABP B-39/RTOG 0413 trial.
Why this matters
- Given low absolute rates of recurrence and similar OS, women with early-stage breast cancer may cautiously consider accelerated PBI.
- 4216 women with a recent lumpectomy with histologically free margins and 0-3 positive axillary nodes were randomly assigned to PBI for 5-10 days (n= 2107) or WBI for 5-6 weeks (n= 2109).
- Funding: NIH.
- Dr. Vicini is a research advisor for ImpediMed.
- Median follow-up, 10.2 years.
- 10-year IBTR rate was higher with accelerated PBI vs WBI (4.6% vs 3.9%; HR, 1.22; 90% CI, 0.94-1.58), with an absolute difference of 0.7%.
- Accelerated PBI missed primary endpoint for noninferiority, defined as 90% CI between 0.667 and 1.5 for HR.
- 10-year recurrence-free survival was lower with accelerated PBI (91.9% vs 93.4%; HR, 1.33; P=.02).
- Accelerated PBI and WBI were similar with respect to:
- Distant disease-free interval at 10 years (96.7% vs 97.1%; P=.15).
- OS (90.6% vs 91.3%; P=.35).
- Accelerated PBI yielded more grade 3 (9.6% vs 7.1%) and grade 4-5 (0.5% vs 0.3%) toxicity.
- QoL and cosmetic data not captured.