Jayasekera J, et al. - Using gene expression profiling (GEP) information with pooled individual-level data, researchers assessed how recurrence and mortality are impacted by the omission of radiotherapy for women with low-risk breast cancer. Results of this study suggested that omitting radiotherapy in hormone-sensitive patients with low recurrence risk could result in a modest increase in locoregional recurrence event rates. However, it did not seem to increase the rate of distant recurrence or death.

Methods

• For this investigation, researchers considered trials that assessed or administered radiotherapy following lumpectomy in women with low-risk breast cancer.
• Included women had experienced lumpectomy and were treated with hormonal therapy for stage I, ER+ and/or PR+, HER2- breast cancer with Oncotype scores no greater than 18.
• Using adjusted Cox models, recurrence-free interval (RFI), type of RFI (locoregional or distant), and breast cancer–specific and overall survival were compared between no radiotherapy and radiotherapy.
• All statistical tests were two-sided in this analysis.

Results

• The final sample was comprised of 1,778 women from seven trials.
• Findings suggested an association of radiotherapy omission with an overall adjusted hazard ratio of 2.59 (95% confidence interval [CI] = 1.38 to 4.89, P=.003) for RFI.
• A statistically significant increase was observed in any first locoregional recurrence (P=.001), but not distant recurrence events (P=.90), or breast cancer–specific (P=.85) or overall survival (P=.61).
• It was noted that five-year RFI rate was high (93.5% for no radiotherapy vs 97.9% for radiotherapy; absolute reduction = 4.4%, 95% CI = 0.7% to 8.1%, P=.03).
• Data reported that the impacts of radiotherapy were different across subgroups, with lower RFI rates for those with Oncotype scores of less than 11 (vs 11–18), older (vs younger), and ER+/PR+ status (vs other).