MAINTAIN Trial: Ribociclib After Prior CDK4/6 Inhibitor Use

MAINTAIN Trial: Switching to Ribociclib

Source

Source: Kalinsky K, Accordino MK, Chiuzan C, et al. Randomized Phase II Trial of Endocrine Therapy With or Without Ribociclib After Progression on Cyclin-Dependent Kinase 4/6 Inhibition in Hormone Receptor–Positive, Human Epidermal Growth Factor Receptor 2–Negative Metastatic Breast Cancer: MAINTAIN Trial. J Clin Oncol. 2023.

First randomized evidence supporting the switch to Ribociclib with Endocrine Therapy after progression on prior CDK4/6 inhibitor treatment.

Study Architecture

Population (N=119)

HR+/HER2– metastatic breast cancer. Progressed on prior ET + CDK4/6i (86.5% prior palbociclib).

Study Design

Phase II, Randomized, Double-blind, Placebo-controlled. Median follow-up: 18.2 months.

Intervention

Arm A: Switch ET + Ribociclib
Arm B: Switch ET + Placebo

Primary Outcome

43%

Reduction in Risk of Progression/Death

HR 0.57 (95% CI, 0.39–0.85; P=.006)

Ribociclib Arm

5.29 mo

Median PFS

Placebo Arm

2.76 mo

Median PFS

Progression-Free Survival

12-Month Benefit

At 1 year, nearly 25% of Ribociclib patients remained progression-free vs <8% on placebo.

Safety Profile

Adverse Event (Grade 3)	Ribociclib	Placebo
Neutropenia	38%	0%
Febrile Neutropenia	3.3%	0%

Febrile neutropenia was rare (2 patients in Ribociclib arm).

Clinical Recommendation

For HR+/HER2– mBC patients progressing on prior CDK4/6i (specifically palbociclib), clinicians should consider switching the endocrine backbone and initiating Ribociclib. This strategy provides significant PFS benefit compared to switching ET alone.