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Lymph node status in stage I hormone receptor-positive/HER2-negative breast cancer was not a good indicator of genetic-risk scores that would qualify older women for adjuvant chemotherapy, researchers found.

Slightly more women 70 years or older with these early breast cancers had chemo-qualifying Oncotype DX 21-gene recurrence scores (>26) if node positive than if node negative (14.7% vs 13.1%).

"There was a statistically significant difference, ... but the absolute difference between these two numbers is quite small," reported Katharine Yao, MD, of NorthShore University HealthSystem in Evanston, Illinois, and the University of Chicago, during a press briefing in advance of the annual meeting of the American Society of Breast Surgeons.

Their results suggest that positive lymph node status is not a reliable indicator of the need for adjuvant chemotherapy, and that sentinel node biopsy "may not be helpful for adjuvant chemotherapy decisions in this patient population," Yao said.

"It probably shouldn't be used to make adjuvant chemotherapy decisions," Yao said. "Perhaps an Oncotype test may be a better option, or even just looking at the clinical tumor factors and the patient's comorbidities and health status."

The Society of Surgical Oncology, in 2016, and the American Society of Breast Surgeons, 2 years later, adopted Choosing Wisely guidelines recommending against routine use of sentinel node biopsy in clinically node negative women ≥70 years of age with early-stage hormone receptive-positive, HER2-negative invasive breast cancer.

Despite these recommendations, Yao reported that a large majority of patients in her study's dataset have undergone sentinel node biopsy, increasing from 81.2% in 2012 to 88.5% in 2018.

"It should be noted that, when you read the statement, there is a provision that axillary staging can be individually considered if the results may impact adjuvant therapy decisions," Yao said. Thus, she and her team hypothesized that many surgeons continue to perform the procedure in order to make adjuvant chemotherapy decisions.

In this study, Yao and her colleagues used the National Cancer Data based to identify 28,338 patients ≥70 years old treated for hormone receptive-positive, HER2-negative breast cancers from 2010 to 2018. Of these patients, 80% were node-negative and the remaining were node-positive.

Yao and colleagues also conducted a multivariable analysis of known clinical factors associated with a high Oncotype score. They found:

• A tumor grade of 3 vs 1 was the strongest factor associated with a high score in both node-positive (OR 12.61, 95% CI 9.16-17.34) and node-negative patients (OR 18.00, 95% CI 15.57-20.81)
• The second strongest factor was negative progesterone receptor status (OR 6.53, 95% CI 4.98-7.71 for node-positive patients; OR 7.19, 95% CI 6.51-7.93 for node-negative)
• Tumor size (>2 cm vs <2 cm) was also associated with high scores, while the number of positive nodes (>1 vs 1) was not
• Compared with White patients, Hispanic patients were less likely to have the higher Oncotype score, whereas Black or Asian patients were not

Yao acknowledged certain limitations to the study, including significant selection bias. "Oncotype DX is ordered at the clinician's discretion," she said. "We do not know why clinicians ordered the Oncotype DX score. It is not ordered universally for all of these patients."

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