Chemo-Free Regimen with Neoadjuvant CDK 4/6 Inhibition plus Endocrine Therapy Benefits Patients with High-Risk ER+ HER2- Early Breast Cancer

An interview with: Paul H Cottu MD PhD, Medical Oncologist and Associate Professor, Institute Curie, Paris, France

BERLIN, Germany—Patients with high-risk, hormone receptor positive, HER2 negative early breast cancers, who would typically be candidates for chemotherapy, had good clinical responses, high biological responses and good rates of surgery in a clinical trial using a chemotherapy-free neoadjuvant regimen consisting of letrozole hormone therapy plus abemaciclib CDK 4/6 inhibition.

Medical Oncologist Paul Cottu MD PhD from the Institute Curie in Paris, France, reported findings from RIBOLARIS trial at the 2025 Annual Congress of the European Society for Medical Oncology held in Berlin. At his poster during the conference he talked about the study findings with Audio Journal of Oncology reporter Peter Goodwin:

AUDIO JOURNAL OF ONCOLOGY Paul H Cottu MD PhD

IN: “[GOODWIN] I am at the European …..  OUT:  …I’m Peter Goodwin 7:56 secs

ESMO ABTRACT 296O:

“Risk of recurrence (ROR) after neoadjuvant ribociclib plus ET in clinically high-risk ER+/HER2− BC: Preliminary analysis of the SOLTI-RIBOLARIS trial”

Speaker: Paul H. Cottu (Paris, France)

Authors:

Paul H. Cottu (Paris, France) Aleix Prat (Barcelona, Spain) Tomás Pascual (Barcelona, Spain) Huilin Hu (East Hanover, United States of America) Estelle Roux (Basel, Switzerland, NJ) Francisco Javier Salvador Bofill (Seville, Spain) Joana M. Ribeiro (Villejuif, France) Isabel Blancas López-Barajas (Granada, Spain) Thomas Bachelot (Lyon, France) Jerome Lemonnier (Paris, France) Juan M. Ferrero-Cafiero (Barcelona, Spain) Pablo Tolosa Ortega (Madrid, Spain, Valencia) Antonio Mulero-Sánchez (Barcelona, Spain) Thayane Antoniolli Crestani (Brussels, Belgium) Roisin M. Connolly (Cork, Ireland, MD) Cynthia X. Ma (St. Louis, United States of America) Antonio C. Wolff (Baltimore, United States of America, MD) Guillermo Villacampa (Barcelona, Spain) Thibault De La Motte Rouge (Rennes, France) Joaquín Gavilá-Gregori (Valencia, Spain)

Background

The CDK4/6 inhibitors (CDK46/i) are approved for early-stage HR+/HER2− breast cancer (BC). The randomized neoadjuvant NeoPAL and CORALLEEN trials provided proof of concept that CDK4/6i in combination with endocrine therapy (ET) have similar activity to multi-agent chemotherapy in pts with luminal B-PAM50 based- BC subtype. The PAM50-derived ROR score was identified as an endpoint of interest after neoadjuvant CDK4/6i-ET. The RIBOLARIS trial was designed to evaluate whether pts with ROR-low disease following neoadjuvant ribociclib (RIB) and ET can safely omit adjuvant chemotherapy.

Methods

RIBOLARIS is an open-label, single-arm, multicenter trial in pts with primary operable stage II, grade 2/3, Ki67 ≥20%, HR+/HER2− BC who are candidates for adjuvant chemotherapy. The study evaluates safety and long-term efficacy of a non-chemo regimen (RIB-ET) in pts with tumors showing a ROR-low score after 6 neoadjuvant cycles of RIB-ET (600 mg/day 3 weeks ON/1 week OFF + ET: letrozol 2.5 mg/day) followed by surgery (within 10 days). Pts with ROR-med/high tumors will receive chemotherapy-based treatment followed by RIB-ET. This preplanned Interim Analysis analyzed safety and efficacy after 686 surgeries. We expected at least 40% of the pts to achieve a ROR-low score after neoadjuvant RIB-ET.

Results

Among the enrolled pts, baseline characteristics included: median age 57 (38-84), postmenopausal status 62%, tumor stage IIA 60%, node-negative 60%, and histological grade 2 74%. At data cut-off, 686 out of 1100 surgeries (62.4%) were performed. Interestingly, we observed that 361 pts (52.6%) achieved a ROR-low score (Mean 11.3, 95% CI 10.5-12.2), while 325 pts (47.4%) had a med/high ROR score (Mean 36.9, 95% CI 34.2-39.5). The most common grade 3-4 severity TEAEs were neutropenia (grade 3: 46.3%; grade 4: 3.5%) and transaminases increased (grade 3: 10.4%; grade 4: 1.5%).

Conclusions

These preliminary results from the RIBOLARIS trial confirm and extend the findings from CORALLEEN and NeoPAL trials, demonstrating that a subset of pts with early-stage HR+/HER2− BC achieve ROR-low disease after neoadjuvant RIB-ET and may be candidate to spare chemotherapy. There was no new safety signal.

Clinical trial identification

NCT05296746.