Four trials presented at the San Antonio Breast Cancer Symposium (SABCS) 2022 showed favorable outcomes for patients with hormone receptor (HR)-positive, HER2-negative breast cancer.

The 4-year update of the phase 3 monarchE trial showed increasing benefits with abemaciclib plus endocrine therapy (ET) over ET alone as adjuvant treatment for patients with high-risk early breast cancer.1

The phase 2 RIGHT Choice trial demonstrated the superiority of ribociclib plus ET over chemotherapy in patients with aggressive, advanced breast cancer who had received no prior systemic treatment.2

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In the phase 3 CAPItello-291 trial, combining capivasertib with fulvestrant improved outcomes over fulvestrant alone in patients whose disease had progressed after first-line aromatase inhibitor therapy, with or without a CDK4/6 inhibitor.3 

In the phase 3 EMERALD trial, a longer duration of prior treatment with a CDK4/6 inhibitor was associated with a greater benefit from elacestrant in patients with estrogen receptor (ER)-positive, HER2-negative, advanced breast cancer.4

monarchE: Abemaciclib Provides Lasting Benefits

The 4-year update of the monarchE trial showed that the benefits of abemaciclib increase over time, according to study presenter Stephen R.D. Johnston, MD, PhD, of the Royal Marsden NHS Foundation Trust and the Institute of Cancer Research in London, UK.1

The phase 3 trial ( Identifier: NCT03155997) included 5637 patients with HR-positive, HER2-negative, node-positive, high-risk early breast cancer. Patients were allowed to have received prior (neo)adjuvant chemotherapy.

The patients were randomly assigned to receive ET alone for up to 10 years (n=2829) or ET for up to 10 years plus abemaciclib (150 mg twice daily) for 2 years (n=2808). 

In the preplanned 4-year landmark analysis, the invasive disease-free survival (IDFS) rate was 85.8% with abemaciclib plus ET and 79.4% with ET alone (hazard ratio, 0.664; 95% CI, 0.578-0.762; <.0001). The difference in IDFS favoring abemaciclib was 6.4% at 4 years, an increase from the 2.8% difference seen at 2 years and the 4.8% difference seen at 3 years.

At 4 years, the distant relapse-free survival (DRFS) rate was 88.4% with abemaciclib plus ET and 82.5% with ET alone (hazard ratio, 0.659; 95% CI, 0.567-0.767; P <.0001). The difference in DRFS favoring abemaciclib was 5.9% at 4 years, an increase from the 2.5% difference seen at 2 years and the 4.1% difference seen at 3 years. 

The benefits in IDFS and DRFS with abemaciclib were observed regardless of Ki-67 index.

Dr Johnston noted that overall survival (OS) data remain immature, but there were fewer deaths in the abemaciclib arm than in the ET-alone arm (157 vs 173; hazard ratio, 0.929; 95% CI, 0.748-1.153, P =.5027). He added that there were no new safety signals at 4 years.

“This [update] is the one that we’ve been waiting for,” study investigator Matthew P. Goetz, MD, of the Mayo Clinic in Rochester, Minnesota, said in an interview.

He noted that, although prior results from monarchE showed a benefit with abemaciclib, it wasn’t clear if that benefit would persist.5,6 The 4-year update shows a sustained benefit in IDFS and DRFS.1

“It looks like once you stop the drug, the hazard ratios, if anything, are getting larger, which is surprising, but it is also really good news for patients,” Dr Goetz said.

The updated results from monarchE were also published in The Lancet Oncology.7