(HealthDay)—The 70-gene signature (GS) assay affects treatment decisions among physicians treating patients identified as being at intermediate risk with the 21-gene assay (21-GA), according to a study published online Oct. 26 in JAMA Oncology.

Michaela Tsai, M.D., from the Virginia Piper Cancer Center in Minneapolis, and colleagues conducted a study involving 840 patients with early-stage breast cancer and a 21-gene assay recurrence score of 18 to 30. Physicians were given the 70-GS result before adjuvant treatment, and the change in physician treatment decision was assessed before versus after receiving the result.

The researchers found that receiving the 70-GS classifications was correlated with a significant change in adjuvant treatment decision, with an odds ratio of 0.64 for all patients. Overall, 28.9 percent of low-risk patients had chemotherapy removed from the treatment recommendation, while 36.7 percent of high-risk patients had chemotherapy added. Results of the 70-GS were associated with the physician's adjuvant treatment recommendation; 87.8 percent of high-risk and 90.6 percent of low-risk patients were recommended to receive adjuvant chemotherapy or no chemotherapy, respectively. In 78.6 percent of cases, physicians reported having more confidence in their treatment recommendations based on 70-GS results.

"The 70-GS provides clinically actionable information regarding patients classified as intermediate risk by the 21-GA and was associated with a change in treatment decision in 282 of these patients (33.6 percent)," the authors write.

Several authors disclosed ties to biopharmaceutical companies, including Agendia Inc., which funded the study.

More information: Abstract/Full Text

Journal information: JAMA Oncology 

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