The following article features coverage from the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting. Click here to read more of Cancer Therapy Advisor‘s conference coverage.

A novel genomic signature can identify breast cancer patients with a low risk of locoregional recurrence (LRR) who may forgo adjuvant radiotherapy, according to study results presented at the 2021 American Society of Clinical Oncology (ASCO) Annual Meeting.

The signature, called POLAR (Profile for the Omission of Local Adjuvant Radiation), can also identify patients who are likely to benefit from radiotherapy, said Martin Sjöström, MD, of the University of San Francisco in California, who presented the study at the meeting.

The study was conducted using data from the SweBCG91-RT trial, in which patients with node-negative, stage I-II breast cancer were randomly assigned to receive adjuvant whole-breast radiotherapy or no radiotherapy following breast-conserving surgery.

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Dr Sjöström and colleagues divided patients into a training cohort (n = 243) and a validation cohort (n = 354). Both cohorts included only patients with estrogen receptor-positive, HER2-negative tumors that had not been treated with adjuvant systemic therapy.

The researchers used the training cohort to identify genes and gene sets that were associated with LRR in patients who did not receive radiotherapy. This led to the development of a 16-gene signature, POLAR, that was then tested in the validation cohort.

In a multivariable analysis adjusted for age, grade, tumor size, and subtype (luminal A vs luminal B), POLAR was prognostic for LRR (hazard ratio [HR], 1.7; 95% CI, 1.2-2.3; P <.001).

Radiotherapy did not confer a significant benefit in LRR among patients categorized as low risk by POLAR (HR, 1.1; 95% CI, 0.38-3.3; P =.83) but did confer a significant benefit in patients who were high risk by POLAR (HR, 0.43; 95% CI, 0.24-0.78; P =.0053).

Among low-risk patients, the 10-year LRR rate was 5% with radiotherapy and 7% without it. In high-risk patients, the 10-year LRR rate was 8% and 19%, respectively.

“[O]ur data indicate that the novel POLAR genomic signature might identify patients that have a low risk of low-grade recurrence without adjuvant radiotherapy after breast-conserving surgery and . . . are therefore candidates for radiotherapy omission,” Dr Sjöström concluded.

Disclosures: This research was supported by PFS Genomics and others. Some study authors declared affiliations with biotech, pharmaceutical, and/or device companies. Please see the original reference for a full list of disclosures.

Read more of Cancer Therapy Advisor’s coverage of the 2021 ASCO Annual Meeting by visiting the conference page.


Sjöström M, Chang SL, Hartman L, et al. Discovery and validation of a genomic signature to identify women with early-stage invasive breast cancer who may safely omit adjuvant radiotherapy after breast-conserving surgery. J Clin Oncol. 2021;39:(suppl 15; abstr 512). doi:10.1200/JCO.2021.39.15_suppl.512