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NATALEE (gene-expression analysis) — Ribociclib + nonsteroidal aromatase inhibitor, adjuvant HR+/HER2− stage II/III early breast cancer

Abstract: 501 · Session: Breast Cancer — Oral Abstract Session, Sat May 30, 2026 (CT) · Presenter: NATALEE investigators (named presenter not yet confirmed) · Embargo: per ASCO 2026 release

At a glance

  • Sponsor: Novartis
  • PI / presenter: Dennis J. Slamon (NATALEE study chair); ASCO 2026 abstract presenter not yet confirmed
  • NCT ID: NCT03701334
  • Phase: III (this report = exploratory biomarker substudy)
  • Design: Randomized, open-label, adjuvant ribociclib (400 mg, 3-weeks-on/1-off, ×3 yr) + NSAI vs NSAI alone; this analysis correlates baseline tumor gene expression (PAM50 intrinsic subtype) with iDFS
  • N: 3,022 baseline surgical tumor samples profiled
  • Primary endpoint(s): Parent trial — invasive disease–free survival (iDFS). This analysis — prognostic/predictive value of baseline gene expression / PAM50 subtype
  • Comparator: NSAI alone
  • Indication: HR+/HER2− stage II/III early breast cancer (adjuvant)
  • Line: Adjuvant (post-surgery)

Headline result

In an exploratory analysis of 3,022 baseline surgical samples from the phase III NATALEE trial, adjuvant ribociclib iDFS benefit was consistent across all PAM50 intrinsic subtypes, with no subtype × treatment interaction. Subtype-specific hazard ratios were luminal A 0.77, luminal B 0.71, HER2-enriched 0.50, and basal-like 0.42 (range HR 0.42–0.77), all favoring ribociclib + NSAI. The investigators concluded that ribociclib benefit is not confined to any single intrinsic subtype, and that baseline gene-expression profiling may help refine prognostic risk stratification in HR+/HER2− early breast cancer rather than select for or against treatment.

Mechanism / class

Ribociclib is an oral selective CDK4/6 inhibitor that blocks Rb phosphorylation and induces cell-cycle (G1) arrest. Combined with endocrine therapy it is standard of care in HR+/HER2− advanced breast cancer (MONALEESA program) and, on the strength of NATALEE, is FDA-approved (Sep 2024) for adjuvant treatment of stage II/III HR+/HER2− early breast cancer at high risk of recurrence.

Practice-changing?

Pending / supportive rather than practice-changing on its own. The analysis reinforces broad use of adjuvant ribociclib across PAM50 subtypes (no subtype should be excluded from benefit) and positions baseline gene expression as a risk-stratification—not treatment-selection—tool. It does not change current eligibility, which remains clinical/anatomic.

  • AACR 2026: ../../aacr-2026/index.md
  • Other ASCO 2026 trials: see Breast track index
  • JPM 2026: ../../jpm-2026/index.md

Sources

  • ASCO Meeting Library: abstract 501, 2026 ASCO Annual Meeting (asco.org/abstracts)
  • Docwire News — "ASCO 2026: Baseline Gene Expression May Refine Risk Stratification in HR+/HER2− Early Breast Cancer": https://www.docwirenews.com/post/asco-2026-baseline-gene-expression-may-refine-risk-stratification-in-hr-her2%E2%88%92-early-breast-cancer
  • OncoDaily — "25 Posts Not To Miss From ASCO 2026 Day 2": https://oncodaily.com/not-to-miss/not-to-miss-asco-512178
  • OncLive — "Poll Results Highlight Breast Cancer Abstracts of Interest at ASCO 2026": https://www.onclive.com/view/poll-results-highlight-breast-cancer-abstracts-of-interest-at-asco-2026