Study Validates Test to Predict Breast Cancer Risk

A recent study confirmed that the MammaPrint diagnostic test could identify women with ultralow risk breast cancer, which will allow them to be treated less aggressively, leading to fewer toxic side effects.

MammaPrint is a prognostic and predictive diagnostic test for early-stage breast cancer patients that assesses the risk that a tumor will metastasize to other parts of the body. The test uses RNA isolated from tumor samples and run on custom glass microarray slides in order to determine the expression of a 70-gene signature. The expression profile is then used in a proprietary algorithm to categorically classify the patient as being at either high or low risk of breast cancer recurrence.

The MammaPrint test gives a binary result, high risk or low risk classification, and helps physicians determine whether or not a patient will benefit from chemotherapy. Women with a low risk result can safely forego chemotherapy without decreasing likelihood of disease free survival. MammaPrint is part of the personalized medicine portfolio marketed by Agendia (Amsterdam, The Netherlands).

Investigators at the University of California, San Francisco (USA) collaborated with the Stockholm breast cancer study group (STO) to use the MammaPrint test to evaluate breast cancer patients who had been tracked for decades and were part of a randomized clinical trial of tamoxifen vs no systemic therapy. The STO-3 low-risk trial included 1,780 lymph-node-negative patients with tumors less than or equal to three centimeters in diameter, randomized to two years of adjuvant tamoxifen versus no adjuvant treatment.

The results obtained during the study suggested that in an unscreened population, 15% of women would have ultralow risk tumors. With widespread screening, approximately 25% of postmenopausal women would be diagnosed with ultralow risk breast cancer that would rarely be associated with recurrence or death. For ultralow risk elderly women over age 75 who have other conditions and face a life expectancy of less than a decade, simple excision may be sufficient. Therefore, the 70-gene test could be used to help physicians and patients determine their treatment course, and to inform choice of systemic therapy as well as local therapy.

"This is an important step forward for personalizing care for women with breast cancer," said first author Dr. Laura J. Esserman, professor of surgery and radiology at the University of California, San Francisco. "We can now test small node-negative breast cancers, and if they are in the ultralow risk category, we can tell women that they are highly unlikely to die of their cancers and do not need aggressive treatment, including radiation after lumpectomy. There are breast cancers that pose little or no systemic risk. Women who have a tumor that is classified as ultralow risk by 70-gene signature can be reassured that their long-term outcome is expected to be excellent, with or without endocrine therapy. Having a test that accurately identifies a population of women, who have very little risk to begin with, should be welcomed by patients and clinicians alike. These tools will enable doctors to better personalize therapy to safely minimize treatment and reassure women if a cancer is ultralow risk."

The study was published in the June 29, 2017, online edition of the journal JAMA Oncology.

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