PracticeUpdateEndocrine Therapy With or Without Ribociclib After Progression on CDK4/6 Inhibition in Patients With HR+/HER2− Metastatic Breast Cancer

Improving Progression-Free Survival in Metastatic Breast Cancer: Switching Therapy with Ribociclib

A phase II trial revealed a significant benefit in progression-free survival (PFS) when patients with HR+/HER2- metastatic breast cancer switched endocrine therapy and received ribociclib, offering a new treatment choice after progression on palbociclib.

Key Points:

• A phase II trial called MAINTAIN evaluated the efficacy of switching endocrine therapy (ET) and continuing with the cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) ribociclib in patients with HR+, HER2- metastatic breast cancer who had previously progressed on ET and a CDK4/6i.
• 86.5% of the patients had previously progressed on palbociclib, another CDK4/6i.
• The study showed a statistically significant difference in median progression-free survival (PFS) between patients who received switched ET plus ribociclib (5.29 months) and those who received switched ET plus placebo (2.76 months).

Additional Points:

• CDK4/6 inhibitors are commonly used in combination with ET for HR+/HER2- metastatic breast cancer.
• When patients progress on CDK4/6i and ET, various treatment options are available, including fulvestrant plus alpelisib, elacestrant, PARP inhibitors, and everolimus plus ET.
• Switching ET and continuing a CDK4/6i has been an appealing option for patients who previously had long-term control on treatment.
• The MAINTAIN trial provides evidence for the benefit of switching ET and receiving ribociclib in patients who progressed on ET plus palbociclib.
• Other trials did not demonstrate a benefit of continuing palbociclib after progression on palbociclib.
• The available data are from small, randomized phase II trials, with larger phase III trial data pending.

Conclusion:

• The MAINTAIN trial demonstrated a significant progression-free survival benefit for patients with HR+/HER2- metastatic breast cancer who switched endocrine therapy and received ribociclib compared to those who received placebo after previous CDK4/6i and different endocrine therapy.

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Did You Know?
Endocrine therapy is estimated to reduce the risk of breast cancer recurrence by approximately 40-50% in hormone receptor-positive breast cancer patients, making it a vital treatment strategy for long-term disease control.