The following is a summary of “Development and Validation of a Genomic Profile for the Omission of Local Adjuvant Radiation in Breast Cancer,” published in the March 2023 issue of Oncology by Sjöström, et al.

For a study, researchers sought to identify women with early-stage invasive breast cancer who may not require adjuvant radiotherapy (RT) after breast-conserving surgery. 

The study involved two randomized trials of women with node-negative invasive breast cancer who underwent breast-conserving surgery and either received or did not receive RT: SweBCG91-RT (stage I-II, no adjuvant systemic therapy) and Princess Margaret (age 50 years or older, T1-T2, adjuvant tamoxifen). The researchers analyzed transcriptome-wide profiling data obtained through Affymetrix Human Exon 1.0 ST microarrays for patients with estrogen receptor–positive/human epidermal growth factor receptor 2–negative tumors. The study’s main objective was to develop a molecular-based approach to identify women with a low risk of recurrence who may not require RT after breast-conserving surgery. The SweBCG91-RT cohort was divided into training (N = 243) and validation (N = 354) cohorts. Using elastic net regression, they created a 16-gene signature named Profile for the Omission of Local Adjuvant Radiation (POLAR) to predict locoregional recurrence (LRR). They then validated POLAR in both the SweBCG91-RT and Princess Margaret cohorts. 

Patients categorized as POLAR low-risk who did not receive RT had a 10-year LRR of 6% (95% CI, 2 to 16) and 7% (0 to 27) in SweBCG91-RT and Princess Margaret cohorts, respectively. There was no significant benefit from RT in POLAR low-risk patients (hazard ratio [HR], 1.1 [0.39 to 3.4], P = .81, and HR, 1.5 [0.14 to 16], P = .74, respectively). On the other hand, patients categorized as POLAR high-risk had a significantly decreased risk of LRR with RT (HR, 0.43 [0.24 to 0.78], P = .0055, and HR, 0.25 [0.07 to 0.92], P = .038, respectively).

The study’s results suggested that the POLAR genomic signature may identify patients with a low risk of LRR who may not require RT after breast-conserving surgery. By sparing these patients from RT, they may avoid the potential side effects of the treatment while still receiving appropriate care for their condition. However, further research was needed to confirm the findings and determine the best way to integrate POLAR into clinical practice

Reference: ascopubs.org/doi/full/10.1200/JCO.22.00655