- For estrogen receptor-positive (ER+) early breast cancer, endocrine therapy (ET) with whole breast irradiation (WBI) offers superior DFS vs ET alone.
- Results are from the 10-year Austrian Breast and Colorectal Cancer Study Group 8A trial.
- OS results were similar between groups, but the omission of WBI predicted poorer local recurrence-free survival (LRFS).
Why this matters
- Results suggest that WBI is the best choice for this low-risk group.
- 10-year outcomes of a randomized controlled trial (N=869).
- After breast-conserving surgery, comparison between ET without and with WBI (mean dose, 51±4 Gy, standard fractionation, followed by a tumor bed boost at a mean dose of 10±2 Gy).
- Funding: AstraZeneca.
- Median follow-up, 9.89 years.
- 10-year LRFS:
- 97.5% with WBI vs 92.5% without (P=.0004).
- Translated into higher DFS: 94.5% vs 88.4% (P=.0156).
- Distant metastases-free survival did not differ (96.7% vs 96.4%), and neither did OS (86.6% vs 87.6%).
- Negative predictors of LRFS:
- No WBI (vs WBI): HR, 0.27 (P=.0006).
- Higher tumor grade (Gx vs G1): HR, 3.76 (P=.028).
- Open-label design.