Dr O'Shaughnessy on MammaPrint H1 vs H2 Status on 3-year RFS in HR+, HER2– Breast Cancer

Joyce O'Shaughnessy, MD, chair, Breast Cancer Research, chair, Breast Cancer Prevention Research, Baylor-Sammons Cancer Center, discusses the impact of MammaPrint High 1 (H1) and High 2 (H2) status on 3-year relapse-free survival (RFS) in patients with early-stage hormone receptor (HR)–positive, HER2-negative breast cancer who received adjuvant chemotherapy with either a taxane plus cyclophosphamide (TC) or anthracycline plus a taxane and cyclophosphamide (ATC).

The prospective, observational FLEX registry trial (NCT03053193) focused on patients with early-stage, HR-positive, HER2-negative breast cancer with MammaPrint H1 or H2 disease, O'Shaughnessy begins. Patients were not randomized; rather, a chemotherapy regimen of TC or ATC was selected by their physicians based on clinical judgment, she adds.

Findings presented at the 2024 ASCO Annual Meeting showed that patients with MammaPrint H1 disease experienced similar 3-year RFS whether they were treated with TC or ATC, O'Shaughnessy say. Patients treated with ACT (n = 184) achieved a 3-year RFS rate of 95.3% (95% CI, 91.8%-98.8%) compared with 97.1% (9%% CI, 95.1%-99.2%) for thos given TC (n = 346). In contrast, patients with MammaPrint H2 disease experienced improved 3-year RFS outcomes when treated with ACT compared with TC, she notes. The 3-year RFS rates in this population were 97.7% (95% CI, 93.4%-100%) for ACT (n = 44) compared with 86.4% (95% CI, 74.2%-100%) for TC (n = 40). This suggests that anthracycline-containing regimens may be particularly important for patients with H2 disease, she notes.

For patients with MammaPrint H2 disease, O'Shaughnessy says these data lean her toward recommending anthracycline-containing regimens based on the RFS improvement seen in the FLEX trial. However, for MammaPrint H1 patients, she says the data do not currently support fully backing away from anthracycline use in this patient population, and she notes it is important to consider all individual clinical and pathological features available to make treatment decisions, including H1 or H2 status.