Utility of the 70-Gene MammaPrint Assay for Prediction of Benefit From Extended Letrozole Therapy in the NRG Oncology/NSABP B-42 Trial

Priya Rastogi; Hanna Bandos; Peter C Lucas; Laura J van 't Veer; Jia-Perng J Wei; Charles E Geyer Jr; Louis Fehrenbacher; Stephen K L Chia; Adam M Brufsky; Janice M Walshe; Gamini S Soori; Shaker R Dakhil; Soonmyung Paik; Sandra M Swain; Andrea R Menicucci; M William Audeh; Norman Wolmark; Eleftherios P Mamounas

doi:10.1200/JCO.23.01995

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Utility of the 70-Gene MammaPrint Assay for Prediction of Benefit From Extended Letrozole Therapy in the NRG Oncology/NSABP B-42 Trial

Authors: Priya Rastogi ; Hanna Bandos ; Peter C Lucas ; Laura J van 't Veer ; Jia-Perng J Wei ; Charles E Geyer Jr ; Louis Fehrenbacher ; Stephen K L Chia ; Adam M Brufsky ; Janice M Walshe ; Gamini S Soori ; Shaker R Dakhil ; Soonmyung Paik ; Sandra M Swain ; Andrea R Menicucci ; M William Audeh ; Norman Wolmark ; Eleftherios P Mamounas

Citation: JOURNAL OF CLINICAL ONCOLOGY, Vol.42(30) : 3561-3569, 2024-10

Journal Title: JOURNAL OF CLINICAL ONCOLOGY

ISSN: 0732-183X

Issue Date: 2024-10

MeSH: Adult ; Aged ; Antineoplastic Agents / therapeutic use ; Aromatase Inhibitors / therapeutic use ; Breast Neoplasms* / drug therapy ; Breast Neoplasms* / pathology ; Disease-Free Survival ; Female ; Gene Expression Profiling ; Humans ; Letrozole* / administration & dosage ; Letrozole* / therapeutic use ; Middle Aged ; Nitriles* / therapeutic use ; Predictive Value of Tests ; Risk Assessment ; Triazoles* / administration & dosage ; Triazoles* / therapeutic use

Abstract: Purpose: MammaPrint (MP) determines distant metastatic risk and may improve patient selection for extended endocrine therapy (EET). This study examined MP in predicting extended letrozole therapy (ELT) benefit in patients with early-stage breast cancer (BC) from the NSABP B-42 trial.

Patients and methods: MP was tested in 1,866 patients randomly assigned to receive ELT or placebo. The primary end point was distant recurrence (DR). Secondary end points were disease-free survival (DFS) and BC-free interval (BCFI). Tumors were classified as MP high risk (MP-HR) or low risk (MP-LR). MP-LR tumors were further classified as ultralow risk (MP-UL) or low non-ultralow risk (MP-LNUL).

Results: There was no statistically significant difference in ELT benefit on DR between MP-HR and MP-LR (interaction P = .38). MP-LR tumors (n = 1,160) exhibited a statistically significant 10-year benefit of 3.7% for DR (hazard ratio [HR], 0.43 [95% CI, 0.25 to 0.74]; P = .002), whereas MP-HR tumors (n = 706) exhibited a nonsignificant 2.4% benefit (HR, 0.65 [95% CI, 0.34 to 1.24]; P = .19). The 10-year ELT benefit was significant for DFS (7.8%) and BCFI (7.0%) for MP-LR tumors, whereas MP-HR tumors did not significantly benefit (interaction DFS: P = .015, BCFI: P = .006). In exploratory analysis, the 10-year ELT benefit was significant and more pronounced in MP-LNUL (n = 908) tumors: 4.0% for DR, 9.5% for DFS, and 7.9% for BCFI; the benefit in MP-UL (n = 252) tumors was not significant: 3% for DR, 1.8% for DFS, and 4.1% for BCFI.

Conclusion: The primary hypothesis of predictive ability of MP on DR was not confirmed. However, the secondary outcomes demonstrated MP was predictive of ELT response and identified a subset of patients with early-stage hormone receptor-positive BC (MP-LR) with improved outcomes from ELT. These data could have important clinical implications in patient selection beyond clinical risk assessment for EET.