Benefit Seen With Ribociclib in Most Breast Cancer Subtypes

In Clinical Studies News by Barbara Jacoby

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By: Andrea S. Blevins Primeau, PhD, MBA

From: cancertherapyadvisor.com

In an exploratory analysis of intrinsic breast cancer subtypes, ribociclib plus endocrine-based therapy was found to be effective against all subtypes except basal-like, according to the results of a retrospective analysis published in the Journal of Clinical Oncology.

Previous studies have suggested that intrinsic breast cancer subtypes are independently associated with survival and are prognostic in hormone receptor-positive, HER2-negative disease treated with endocrine therapy. However, “…the value of intrinsic subtypes in the context of endocrine therapy plus CDK4/6 inhibition is unclear,” according to this study’s authors.

The retrospective study analyzed data from 1160 tumors that had been treated with endocrine therapy plus ribociclib or placebo in the MONALEESA-2, -3, and -7 trials (ClinicalTrials.gov Identifier: NCT01958021, NCT02422615, and NCT02278120, respectively). PAM50 analysis was used to determine intrinsic tumor subtypes. The primary objective was to assess the association of PAM50-based intrinsic tumor subtypes with progression-free survival (PFS).

The intrinsic subtypes of the tumors sampled were luminal A (46.7%), luminal B (24.0%), normal-like (14.0%), HER2-enriched (12.7%), and basal-like (2.6%).

Regardless of treatment, intrinsic subtype was independently associated with PFS, with the longest PFS associated with the luminal A subtype (P =.0007), and the shortest PFS associated with HER2-enriched and basal-like subtypes (P <.001).

Except for the basal-like type, all other intrinsic subtypes demonstrated shorter PFS with ribociclib compared with placebo. For luminal A, the hazard ratio (HR) was 0.63 (95% CI, 0.49-0.83; P =.0007) for ribociclib compared with placebo. The HR for luminal B was 0.52 (95% CI, 0.38-0.72; P <.001), for HER2-enriched was 0.39 (95% CI, 0.25-0.60; P <.001), and for normal-like was 0.47 (95% CI, 0.30-0.72; P <.001). For the basal-like subtype, the HR was 1.15 (95% CI, 0.46-2.83; P =.77).

The study authors concluded that “…patients in the MONALEESA trials exhibited a consistent substantial PFS benefit from ribociclib across all subtypes except basal-like.” They added that “Following our results, the question remains whether intrinsic subtyping should guide the use of CDK4/6 inhibitors in [advanced breast cancer].”

Disclosure: Please see the original article for a link to the full list of authors’ affiliations.

Reference

Prat A, Chaudhury A, Solovieff N, et al. Correlative biomarker analysis of intrinsic subtypes and efficacy across the MONALEESA phase III studies. J Clin Oncol. Published online March 26, 2021. doi:org/10.1200/JCO.20.02977