Genetic test identifies ultralow-risk breast cancers
medwireNews: The 70-gene MammaPrint assay can identify women who have an ultralow risk for death from breast cancer in the long term, potentially allowing their physicians to choose less aggressive treatment, say researchers.
They write: “We have used a molecular classifier to demonstrate long-term indolent tumor behavior. Such tools, if integrated into screening, treatment, and trials, can prevent inadvertent overtreatment and enable excellent outcomes with less toxic effects.”
As even clinically low-risk tumors carry a recurrence risk, the team used the US Food and Drug Administration-approved MammaPrint test to identify an ultralow-risk threshold below which there were no breast cancer-related deaths among node-negative patients over a 15-year period in the absence of systemic therapy.
This ultralow-risk threshold was validated in the current study, involving 652 postmenopausal women with node-negative tumors no larger than 3 cm who were randomly assigned to receive adjuvant tamoxifen or no systemic therapy in the Swedish STO-3 trial conducted from 1976 to 1990.
The risk for breast cancer-specific mortality differed significantly by the MammaPrint risk category, such that patients with high- and low-risk disease had an increased long-term risk relative to those classified as ultralow risk, with adjusted hazard ratios of 4.73 and 4.54, respectively.
Among the 15% of participants in the ultralow-risk category, there were no breast cancer-specific deaths at 15 years for tamoxifen-treated patients. And the 20-year breast cancer-specific survival rates were 97% in the tamoxifen group and 94% for those who did not receive any systemic therapy.
Laura Esserman (University of California–San Francisco, USA) and study co-authors write in JAMA Oncology that “[w]omen who have a tumor that is an ultralow-risk tumor by 70-gene signature can be reassured that their long-term outcome is expected to be excellent, with or without endocrine therapy.”
They add: “With the updated American Society of Clinical Oncology guidelines of 10 years of adjuvant endocrine therapy for patients with hormone receptor–positive breast cancers, 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.”
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