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. 2022 Mar;33(3):310-320.
doi: 10.1016/j.annonc.2021.11.014. Epub 2021 Dec 1.

Outcome without any adjuvant systemic treatment in stage I ER+/HER2- breast cancer patients included in the MINDACT trial

J M N Lopes Cardozo  1 , D Byng  2 , C A Drukker  3 , M K Schmidt  4 , M A Binuya  5 , L J van 't Veer  6 , F Cardoso  7 , M Piccart  8 , C H Smorenburg  9 , C Poncet  10 , E J T Rutgers  11
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Free article

Outcome without any adjuvant systemic treatment in stage I ER+/HER2- breast cancer patients included in the MINDACT trial

J M N Lopes Cardozo et al. Ann Oncol. 2022 Mar.
Free article

Abstract

Background: Adjuvant systemic treatments (AST) reduce mortality, but have associated short- and long-term toxicities. Careful selection of patients likely to benefit from AST is needed. We evaluated outcome of low-risk breast cancer patients of the EORTC 10041/BIG 3-04 MINDACT trial who received no AST.

Patients and methods: Patients with estrogen receptor-positive, HER2-negative, lymph node-negative tumors ≤2 cm who received no AST were matched 1 : 1 to patients with similar tumor characteristics treated with adjuvant endocrine therapy (ET), using propensity score matching and exact matching on age, genomic risk (70-gene signature) and grade. In a post hoc analysis, distant metastasis-free interval (DMFI) and overall survival (OS) were assessed by Kaplan-Meier analysis and hazard ratios (HR) by Cox regression. Cumulative incidences of locoregional recurrence (LRR) and contralateral breast cancer (CBC) were assessed with competing risk analyses.

Results: At 8 years, DMFI rates were 94.8% [95% confidence interval (CI) 92.7% to 96.9%] in 509 patients receiving no AST, and 97.3% (95% CI 95.8% to 98.8%) in 509 matched patients who received only ET [absolute difference: 2.5%, HR 0.56 (95% CI 0.30-1.03)]. No statistically significant difference was seen in 8-year OS rates, 95.4% (95% CI 93.5% to 97.4%) in patients receiving no AST and 95.6% (95% CI 93.8% to 97.5%) in patients receiving only ET [absolute difference: 0.2%, HR 0.86 (95% CI 0.53-1.41)]. Cumulative incidence rates of LRR and CBC were 4.7% (95% CI 3.0% to 7.0%) and 4.6% (95% CI 2.9% to 6.9%) in patients receiving no AST versus 1.4% (95% CI 0.6% to 2.9%) and 1.5% (95% CI 0.6% to 3.1%) in patients receiving only ET.

Conclusions: In patients with stage I low-risk breast cancer, the effect of ET on DMFI was limited, but overall significantly fewer breast cancer events were observed in patients who received ET, after the relatively short follow-up of 8 years. These benefits and side-effects of ET should be discussed with all patients, even those at a very low risk of distant metastasis.

Keywords: breast cancer recurrence; endocrine therapy; low-risk breast cancer; no adjuvant systemic treatment.

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Conflict of interest statement

Disclosure LJvV reports being shareholder in and part-time employed by Agendia NV, the commercial company that markets the 70-gene signature as MammaPrint. FC has received personal fees from Amgen, Astellas/Medivation, AstraZeneca, Celgene, Daiichi-Sankyo, Eisai, GE Oncology, Genentech, GlaxoSmithKline, Macrogenics, Medscape, Merck-Sharp, Merus BV, Mylan, Mundipharma, Novartis, Pfizer, Pierre-Fabre, prIME Oncology, Roche, Samsung Bioepis, Sanofi, Seagen and Teva outside the submitted work. MP reports grants from Radius, Synthon and Servier; grants and personal fees from AstraZeneca, Lilly, MSD (Merck-Sharp & Dohme), Novartis, Odonate, Pfizer, Roche-Genentech, Menarini and Immunomedics; and personal fees from Camel-IDS, Debiopharm, Seattle Genetics, Oncolytics and Immutep, all outside the submitted work. EJTR reports personal fees from Guerbet. All other authors have declared no conflicts of interest.

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