Would you keep treating with CDK4/6 inhibitors and just switch endocrine therapy after failing first line ET+CDK4/6 inhibitor? This trial says YES.
Cyclin-dependent kinase 4/6 inhibitor (CDK4/6i) with endocrine therapy (ET) improves progression-free survival (PFS) and overall survival (OS) in hormone receptor–positive (HR+), human epidermal growth factor receptor 2–negative (HER2–) metastatic breast cancer (MBC). Although preclinical and clinical data demonstrate a benefit in changing ET and continuing a CDK4/6i at progression, no randomized prospective trials have evaluated this approach.
In this investigator-initiated, phase II, double-blind placebo-controlled trial in patients with HR+/HER2– MBC whose cancer progressed during ET and CDK4/6i, participants switched ET (fulvestrant or exemestane) from ET used pre-random assignment and randomly assigned 1:1 to the CDK4/6i ribociclib versus placebo. PFS was the primary end point, defined as time from random assignment to disease progression or death. Assuming a median PFS of 3.8 months with placebo, we had 80% power to detect a hazard ratio (HR) of 0.58 (corresponding to a median PFS of at least 6.5 months with ribociclib) with 120 patients randomly assigned using a one-sided log-rank test and significance level set at 2.5%.
Of the 119 randomly assigned participants, 103 (86.5%) previously received palbociclib and 14 participants received ribociclib (11.7%). There was a statistically significant PFS improvement for patients randomly assigned to switched ET plus ribociclib (median, 5.29 months; 95% CI, 3.02 to 8.12 months) versus switched ET plus placebo (median, 2.76 months; 95% CI, 2.66 to 3.25 months) HR, 0.57 (95% CI, 0.39 to 0.85); P = .006. At 6 and 12 months, the PFS rate was 41.2% and 24.6% with ribociclib, respectively, compared with 23.9% and 7.4% with placebo.
In this randomized trial, there was a significant PFS benefit for patients with HR+/HER2– MBC who switched ET and received ribociclib compared with placebo after previous CDK4/6i and different ET.
The INSEMA trial showed that for early stage, T1-T2 clinically node negative breast cancer, sentinel lymph node biopsies should not be mandatory, and best clinical judgement can be used.
Imlunestrant (novel oral SERD) was active in patients with an ESR1 mutations, but otherwise did not offer a benefit in this population of women with ER+ HER2-neg MBC. Overall survival (OS) data is pending with further follow up.
Yet another combination to consider after CDK4/6i + ET in HR+ MBC!
Another trial with neoadjuvant immunotherapy showing improved results over chemotherapy alone. (12% higher PCR 48% vs 36%).
Dato-DXd is now approved in HR+, HER2-neg, metastatic breast cancer after prior therapy with endocrine-based therapy and chemotherapy. There was an impressive reduction in the risk of death or progression with an HR of 0.63. Watch out for ocular and pulmonary toxicity. HER2-ultra low testing will be burdensome but must be done for drug approval.
FCS Hematology Oncology Review creates a platform for our physician network to observe the most recent articles and studies available in the oncology and hematology world. By sharing these articles we are building our wealth of knowledge of new observations and treatments as they come available.
