Breast Cancer Coverage From Every Angle
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Using Molecular Signature to Identify Indolent Breast Tumors

An ultralow-risk threshold of the MammaPrint 70-gene expression score seems to be capable of identifying patients with node-negative disease who have a low long-term systemic risk of death from breast cancer after surgery alone. Laura J. Esserman, MD, MBA, of Helen Diller Family Comprehensive Cancer Center, University of California, San Francisco, and colleagues reported the findings of their analysis in JAMA Oncology. Although the frequency of cancers with indolent behavior has increased with screening, the investigators stressed the importance of finding better tools to identify indolent tumors to avoid overtreatment.

This secondary analysis involved postmenopausal women with node-negative tumors up to 3 cm. Enrolled in the Stockholm tamoxifen (STO-3) trial, these women were randomized to receive tamoxifen or no adjuvant therapy after mastectomy or lumpectomy and radiation therapy. This study was conducted between 1976 and 1990—in the era before mammography screening.

Among the 652 women with MammaPrint scoring available, the risk level was high for 275 patients (42%), low for 377 patients (58%), and ultralow for 98 patients (15%). At 20 years, those with 70-gene high and low tumors—but not ultralow tumors—had a higher risk of disease-specific death. At 15 years, there were no deaths in the ultralow-risk tamoxifen-treated patients. At 20 years, the breast cancer–specific survival rate was 97% in these ultralow-risk tamoxifen recipients, compared with 94% in untreated patients.