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Breast Cancer Patients With Low Genomic Recurrence Risk May Eschew Chemotherapy

NEW YORK (GenomeWeb) – Women with early-stage breast cancer who are at high clinical risk of recurrence might not need adjuvant chemotherapy if they are at low genomic risk.

In a randomized phase 3 study, researchers from the Microarray in Node-negative and 1 to 3 positive lymph node Disease may Avoid ChemoTherapy (MINDACT) study assessed the clinical and genomic risk of disease recurrence in nearly 6,700 women with early-stage breast cancer. As Martine Piccart from Université Libre de Bruxelles and her colleagues reported this week in the New England Journal of Medicine, they gauged clinical risk in this population using Adjuvant! Online and genomic risk using Agendia's MammaPrint test.

Of the patients determined to be at high clinical risk, but low genomic risk, there was a slight difference in survival between the patients who received chemotherapy versus those who did not. "We found that chemotherapy with its attendant toxic effects could be avoided in these patients at high clinical risk, but low genomic risk at a cost of a risk of distant metastasis at five years that is 1.5 percentage points higher," Piccart and her colleagues wrote in their paper.

The consortium sought to gauge the clinical utility of Agendia's 70-gene signature test, MammaPrint, when added to standard clinical criteria for determining whether breast cancer patients should undergo adjuvant chemotherapy.

The study divvied the patients into different categories: those at both high clinical and genomic risk of recurrence; those at both low clinical and genomic risk of recurrence; and those who had discordant risk. The discordant patients — of whom there were nearly 2,200, or about a third of patients — where randomized to receive treatment based on either their clinical or genomic risk. That is, about half of the discordant patients received chemotherapy and half did not.

Among patients who had low clinical risk, but high genomic risk, those who received chemotherapy had a five-year rate of survival without distant metastasis of 95.8 percent. By comparison, patients who had low clinical risk but high genomic risk and didn't receive chemotherapy had a five-year rate of survival without distant metastasis of 95.0 percent.

Meanwhile, patients at high clinical risk but low genomic risk who did not receive chemotherapy had a rate of survival without distant metastasis of 94.4 percent, and those with high clinical risk but low genomic risk who did get chemotherapy had a rate of survival without distant metastasis of 95.9 percent. This, the researchers noted, is a 1.5-percentage-point difference between the groups.

The researchers presented a version of these results at the American Association for Cancer Research annual meeting in April.

These results, Piccart and her colleagues said, meant that if the gene signature were used to guide chemotherapy choice, there would be a reduction in the use of adjuvant chemotherapy in 46.2 percent of patients with only a small increase in recurrence risk. This suggested to the researchers that chemotherapy could be avoided for a number of patients who are at low genomic risk of recurrence.

"We understand that a risk-benefit assessment and decisions with respect to the use of adjuvant chemotherapy are highly variable and personalized among physicians and individual patients," Agendia Chief Medical Officer William Audeh said in a statement. "However, these findings provide clinical utility by demonstrating that MammaPrint's accuracy in helping to detect patients with a low risk of distant recurrence could be safely used in the management of over 100,000 women and potentially spare them from unnecessary chemotherapy."

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