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.

Exploratory analysis suggests benefit may be most pronounced in patients with ESR1 wild-type tumors.

AbbreviationsQuick

CDK4/6i, cyclin-dependent kinase 4/6 inhibitor; CI, confidence interval; ctDNA, circulating tumor DNA; ECOG PS, Eastern Cooperative Oncology Group performance status; ET, endocrine therapy; HER2–, human epidermal growth factor receptor 2–negative; HR, hazard ratio; HR+, hormone receptor–positive; MBC, metastatic breast cancer; PFS, progression-free survival.

Bibliography1

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. doi: 10.1200/JCO.22.02392 (DOI: 10.1200/JCO.22.02392 | link)

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