Breast cancer illustration showing one breast with cancerous tissue fluorescing
Credit: ROGER HARRIS/ Getty Images

Women with breast cancer who have a certain genetic signature may be able to avoid radiotherapy after breast conserving surgery, suggests research from the University of Gothenburg.

Different types of surgery are available for breast cancer patients, but women with breast cancer are increasingly opting to have breast conserving surgery as the less radical option. These patients are normally advised to have radiation therapy as well as surgery to reduce the risk of cancer recurrence.

“However, many patients will not experience a local recurrence even without radiation therapy,” said Per Karlsson, a professor of oncology at the Sahlgrenska Comprehensive Cancer Center and the University of Gothenburg in Sweden, who presented the research at the at the San Antonio Breast Cancer Symposium.

“Currently, we do not have any reliable predictive classifiers to identify patients who might be able to skip radiation therapy. Since radiation therapy can be associated with problematic side effects in some patients, it is of clinical importance to identify those patients for whom radiation therapy can be safely omitted.”

In the study, Karlsson and colleagues assessed the value of using a genetic score known as POLAR (Profile for the Omission of Local Adjuvant Radiotherapy), including 16 genes linked to breast cancer risk and prognosis, to assess the need for additional radiotherapy.

They carried out a meta-analysis of three trials—the Swedish SweBCG91RT trial, the Scottish Conservation Trial, and a trial from the Princess Margaret Hospital in Canada—of 623 patients with lymph node-negative, estrogen receptor-positive, HER2-negative breast cancer.

Gene expression in tumor samples was used to create a POLAR score for the participants and the impact of radiation therapy was assessed. In the 429 patients with high POLAR scores, radiation therapy appeared to be beneficial. Overall, 20% of those who did not have radiotherapy had recurrence at 10 years vs. seven percent who did have radiotherapy after surgery.

In contrast, individuals with a low POLAR score (194 patients) experienced little difference in outcome whether or not they had radiotherapy after surgery. At 10 years post-surgery, those who had radiotherapy had a five percent local recurrence vs 7 percent of those who just had surgery.

Karlsson and colleagues now want to test this profile in more patients and further validate their findings so they might be used in the clinic at a future date.

“Although only a minority of patients experience severe side effects to breast radiation, this adds up to a fair number of patients once you consider how prevalent breast cancer is,” he commented. “The POLAR gene profile may, therefore, help mitigate toxicities and improve quality of life for many patients.”

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