By Turna Ray

A study involving Agendia's MammaPrint test has shown that physicians may be able to use the test results alongside other clinical data to withhold chemotherapy for patients with a low risk of recurrence without impacting their five-year survival.

According to Agendia, the study marks the first prospectively designed outcomes trial to gauge whether the use of a molecular diagnostic can impact breast cancer survival by avoiding unnecessary and toxic treatment. Past data on MammaPrint and other breast cancer recurrence diagnostics have shown that such tests impact treatment decisions and can impact survival, but in those investigations, researchers performed genomic analysis retrospectively on samples from patients previously enrolled in large studies.

Data from the Microarray Prognostics in Breast Cancer, or RASTER, study showed that the use of MammaPrint led to a 20 percent reduction in adjuvant chermotherapy use in patients whom the test determined to be at low risk of recurrence.

"Based on our data, the use of the genomic test could lead to a reduction of nearly 30 percent in the use of adjuvant chemotherapy without compromising patient outcomes," lead study investigator Sabine Linn of the Netherlands Cancer Institute said in a statement. In clinical practice, "this percentage may vary somewhat due to different guidelines used in different countries."

In RASTER, between 2004 and 2006, researchers collected fresh tumor samples from 427 women who were younger than 61 years and had breast cancer that hadn't yet spread to the lymph nodes. The researchers then analyzed these samples with MammaPrint, a microarray-based test that measures the expression of 70 genes.

Those patients deemed by MammaPrint to be at high risk of cancer recurrence were provided adjuvant chemotherapy. In the case of patients deemed to be at low risk, physicians considered both the MammaPrint results and clinical factors to decide whether they could avoid receiving such treatment. After patients were treated, study investigators followed them for five years to gauge outcomes.

Within the 219 patients in the low-risk group, 85 percent avoided chemotherapy while the remainder received it because their clinical factors suggested they might benefit from it, Bastiaan van der Baan, VP of sales and marketing at Agendia, told PGx Reporter.

In the high-risk group, meanwhile, 81 percent of 208 patients received chemotherapy.

The low risk group experienced a five-year distant disease-free survival rate of 96 percent versus a DDFS rate of 90 percent in the high-risk group.

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Prospective Outcomes Trial Shows Agendia's MammaPrint Safely Reduces Chemo Use in Low-Risk Patients