Adjuvant ribociclib improves IDFS in early breast cancer

The addition of the CDK4/6 inhibitor ribociclib to adjuvant endocrine therapy improves invasive disease-free survival (IDFS) of patients with early-stage HR-positive/HER2-negative breast cancer, the results of the phase 3 NATALEE trial showed.

Although early breast cancer is treated with curative intent, a considerable risk of disease recurrence remains (27% to 37% for stage II and 46% to 57% for stage III HR-positive/HER2-negative breast cancer) [1]. In patients with advanced HR-positive/HER2-negative breast cancer, the addition of a CDK4/6 inhibitor to endocrine therapy has been shown to increase disease-free and overall survival, while maintaining quality of life [2].

The phase 3 NATALEE trial (NCT03701334) evaluated the addition of the CDK4/6 inhibitor ribociclib to endocrine therapy in 5,101 patients with early-stage HR-positive/HER2-negative breast cancer. Participants were randomised 1:1 to adjuvant treatment with ribociclib (400 mg/day for 3 years) plus endocrine therapy (for at least 5 years) or treatment with endocrine therapy alone. Dr Gabriel Hortobagyi (MD Anderson Cancer Center, TX, USA) presented final results on IDFS, which was the primary endpoint [3]. As of the data cut-off, the median follow-up was 34 months.

The trial met its primary endpoint, as the addition of ribociclib to adjuvant endocrine therapy significantly improved the 3-year IDFS rate: 90.7% versus 87.6% (HR 0.749; P=0.0006). The absolute IDFS benefit at 3 years follow-up was 3.1%. IDFS benefit was observed in all prespecified subgroups. The risk of invasive disease was reduced by 30.0% for stage II disease (3-year IDFS: 94.2% vs 92.6%; HR 0.700) and by 24.5% for stage III disease (3-year IDFS: 88.1% vs 83.8%; HR 0.755). In addition, the 3-year distant disease-free survival rate was significantly improved in patients treated with ribociclib: 92.9% versus 90.2% (HR 0.749; P=0.001). The overall survival data are not yet mature.

“These results further emphasise the significant IDFS benefit of ribociclib in a broad population of patients with HR-positive/HER2-negative early breast cancer at risk of recurrence,” Dr Hortobagyi concluded. However, to put this into perspective, about 30 patients have to be treated with ribociclib for 3 years to receive an IDFS benefit for 1 patient, one of the attendants remarked.

1. Pan H, et al. N Engl J Med 2017;377:1836-1846.
2. Harbeck N, et al. Ther Adv Med Oncol. 2020;12:1758835920943065.
3. Hortobagyi GN, et al. Ribociclib + nonsteroidal aromatase inhibitor as adjuvant treatment in patients with HR+/HER2− early breast cancer: final invasive disease-free survival analysis from the NATALEE trial. Abstract GS03-03, SABCS 2023, 5–9 December, San Antonio, TX, USA.

 

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Posted on 11 January 2024