(ChemotherapyAdvisor) – A prospective community-based observational study has confirmed the additional prognostic value of a genomic signature test to determine which patients with breast cancer need adjuvant systemic therapy following surgery, according to a presentation during the 8th European Breast Cancer Conference in Vienna, Austria, on March 22.

Five-year distant disease-free survival and distant recurrence-free survival rates showed concordance between that predicted by the 70-gene signature (MammaPrint) test and risk predicted by Adjuvant! Online, which was previously assessed.

“If in a comparable cohort diagnosed today the 70-gene signature would be added to standard guidelines used to select patients for adjuvant systemic therapy, a reduction of 29% in the use of adjuvant chemotherapy would be seen,” Sabine Linn, MD, PhD, The Netherlands Cancer Institute, Amsterdam, The Netherlands and colleagues reported. “These findings are important both for quality of life and for cutting down unnecessary healthcare costs.”

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The researchers studied follow-up data from 427 patients with early breast cancer enrolled in the RASTER (MicroarRAy prognoSTics in breast cancER) study. The genomic test was used to predict which patients are at low and high risk of metastasis, enabling optimal patient selection for chemotherapy. The study assessed the feasibility of implementing the test in daily clinical practice in The Netherlands, as well as its effect on adjuvant systemic treatment decisions.

In the group classified as low risk by the genomic test, 15% of 219 patients received adjuvant chemotherapy vs. 81% (169/208) classified as high risk. The first group had a five-year distant disease-free survival rate of 96% vs. 90% in the high-risk group. Where the genomic test predicted a low risk and Adjuvant! Online a high risk, 43% of patients received endocrine therapy and 24%, chemotherapy; five-year distant disease-free survival rate was 98%. Where Adjuvant! Online predicted a low risk but the genomic test a high one, 78% received endocrine therapy and 57% chemotherapy. In this group, five-year distant disease-free survival rate was 95%.

The investigators noted that this is the first study where such a test has been incorporated in decision-making about adjuvant systemic therapy, and results are promising. “It is encouraging to be able to tell patients that we believe they will have just as good a chance of avoiding the recurrence of cancer by not having adjuvant chemotherapy as by having it,” said Dr. Linn.

The researchers will now study two further genomic tests to see whether they can further refine prognosis in the same group of patients with breast cancer. “We will also assess further the cost-effectiveness of the 70-gene signature in comparison with the standard guidelines used to decide whether or not to give adjuvant chemotherapy. We believe that our results already show that the use of genomic tests is feasible and effective in clinical practice, and can help in decision-making,” Dr. Linn concluded.

Abstract (Enter “Linn” in the author box to search for Abstract #207)