Same ol’ story.
The Study: This meta-analysis pooled individual patient data from seven trials that evaluated radiation therapy after lumpectomy in women with low-risk breast cancer. "Low-risk" was defined as ER/PR(+), HER2(-), ≤ cT2 tumors with no nodal involvement. They included women between ages 40 and 74 and also required the Oncotype DX score to be ≤ 18. Finally, all women had to be planning a course of endocrine therapy (but not chemo). Now, the data came from trials that didn't specifically randomize patients +/- radiation. For instance, TAILORx was one of the trials where radiation was dealer's choice, and two trials gave radiation to all women. So, as you'd expect, the women who received no radiation tended to be older and have smaller more favorable tumors. Still, omission of radiation was associated with a 2.5-fold increase in recurrence risk. That meant a 5% absolute increase in locoregional recurrence (1→ 6%) at 5 years and > 11% increase (3 → 15%) at 10 years. Also as expected, there were no differences in distant failure or breast cancer specific survival.
Bottom Line: After adding an Oncotype DX score into the mix, the omission of radiation in women with low-risk breast cancer is still associated with a consistently increased relative risk of locoregional recurrence. | Jayasekera, J Natl Cancer Inst 2018