An analysis of outcomes from a cohort of 1,261 patients from the prospective FLEX study has shown that women with HR+/HER2- early-stage breast cancer who benefit the most from anthracycline-based chemotherapy are those with tumors classified as MammaPrint High Risk 2 and BluePrint Luminal B.
February 12, 2026.
Anthracycline-based chemotherapy is considered one of the most effective adjuvant treatments in early-stage breast cancer. However, its use raises uncertainty due to its short-term toxicity and potential long-term risks, such as cardiotoxicity and secondary leukemia. Therefore, accurately identifying which patients will derive real benefit is key to avoiding unnecessary exposure.
In this context, the NCCN Clinical Practice Guidelines in Oncology recognize in their latest update that MammaPrint® + BluePrint® can help identify a subset of patients with early-stage HR+/HER2- breast cancer who are more likely to benefit from anthracycline-based chemotherapy.
FLEX study results
In patients with tumors classified as MammaPrint High Risk 2 + BluePrint Luminal B, invasive disease-free survival (IDFS) at 3 years was significantly lower with the taxane and cyclophosphamide (TC) regimen, at 89.3%, compared with anthracycline- and taxane-based chemotherapy (AC-T), which reached 100%, representing an absolute benefit of 10.7% with the addition of anthracyclines.
In contrast, in patients with MammaPrint High Risk 1, no significant differences in 3-year IDFS were observed between AC-T (95.6%) and TC (94.6%), suggesting that this subgroup does not derive a clinically meaningful benefit from the addition of anthracyclines.
“I am delighted that oncologists finally have a way to identify HR+/HER2- early breast cancer patients who will benefit from anthracycline therapy,” said Joyce A. O’Shaughnessy, M.D., principal investigator for the FLEX Study. “I think the biologic rationale and the data underpinning the observation that High Risk 2 Luminal (by BluePrint) breast cancer patients benefit from anthracycline therapy are quite strong.”
These results reinforce the role of tumor biology as a central pillar in therapeutic decision-making. Genomic platforms such as MammaPrint® + BluePrint® help advance toward more personalized precision oncology by identifying which patients may truly benefit from anthracyclines and avoiding potentially unnecessary treatment in those unlikely to benefit.
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