Originally published March 26.
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.
RASTER investigators also gauged whether physicians' decision to treat patients with chemo would have changed if another prognostic test, called Adjuvant!Online, was used instead of MammaPrint, and found that the gene expression test placed 20 percent more patients in the low-risk category.
Adjuvant!Online helps physicians decide whether cancer patients are at risk of relapse and should be treated with adjuvant chemotherpy, factoring in patients' age, tumor size, nodal involvement, and histologic grade. Although Adjuvant!Online wasn't used to guide treatment decisions in RASTER, the data show that the two tests were discordant for 35 percent of patients.
For patients whose disease prognosis was low risk by MammaPrint but high risk by Adjuvant!Online, 43 percent received endocrine therapy and 24 percent received chemotherapy. These patients experienced 98 percent DDFS. When Adjuvant!Online gauged patients to be at low risk but Mammaprint determined them to be at high risk, 78 percent received endocrine therapy and 57 percent received chemotherapy. The DDFS for this group was 95 percent.
MammaPrint's US Food and Drug Administration-cleared label indicates the test for use "by physicians as a prognostic marker only, along with other clinicopathological factors."
According to the company, it does not plan to use the RASTER data to get a predictive indication on the label for the test. However, the trial is still ongoing. Van der Baan noted that the company will continue to follow patients for their 10-year disease free survival data.
"We will continue to do research that supports the clinical claims of our products and improves the clinical utility," a company spokesperson told PGx Reporter.
Prospectively designed outcomes trials are expensive and take a long time to complete. As such, few companies in the personalized medicine space have been able to gather prospectively collected validation data on genomic tests, presenting a hurdle when it comes to convincing payors to reimburse for them.
The "findings [from RASTER] are important both for quality of life and for cutting down unnecessary healthcare costs," Linn said in a statement.
Agendia was unable to provide a cost estimate for the prospectively designed trial. RASTER was funded by the Dutch health insurance board CVZ, which determines how standard care is reimbursed in the Netherlands, where the company is headquartered..
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