CDK4/6 inhibitor meta-analysis: overall survival benefit differed by agent

Evidence before this study

We searched PubMed, Web of Science, the Cochrane Library, and Scopus from inception to June 2, 2025, to identify published trials, systematic reviews and meta-analyses on CDK4/6 inhibitors in hormone receptor-positive, HER2-negative advanced breast cancer. We used a combination of MeSH terms and free-text keywords related to “breast cancer”, “CDK4/6 inhibitors”, and “endocrine therapy”. Previous meta-analyses showed significant progression-free survival benefits. However, these studies had several methodological limitations: most relied on aggregate summary statistics rather than patient-level data; several included early-phase or adjuvant trials; subgroup analyses stratified by endocrine-sensitivity status or by individual CDK4/6 agent were either absent or underpowered; and none assessed secondary endpoints such as chemotherapy-free survival, time to first chemotherapy, and duration of response. For overall survival, individual phase 3 trials showed a clear overall survival benefit with ribociclib, abemaciclib had mixed results, and palbociclib did not reach statistical significance. Additionally, comparative pooled estimates across agents and relevant subgroups were not formally evaluated.

Added value of this study

To the best our knowledge, this is the most comprehensive meta-analysis to date assessing CDK4/6 inhibitors plus endocrine therapy in hormone receptor-positive, HER2-negative advanced breast cancer. We reconstructed individual patient data from 11 phase 3 trials involving 6035 patients treated with one of the following CDK4/6 inhibitors: abemaciclib, ribociclib, palbociclib, or dalpiciclib. Use of an reconstruction approach to generate individual patient data enabled granular time-to-event analyses beyond the scope of previous meta-analyses. Our results show that adding a CDK4/6 inhibitor to endocrine therapy significantly improves progression-free survival and overall survival across both endocrine-sensitive and endocrine-resistant populations, with consistent benefits across key subgroups stratified by age, ethnicity, progesterone receptor status, menopausal status, Eastern Cooperative Oncology Group performance status, bone-only disease, and visceral metastasis. However, overall survival benefits were agent-specific: abemaciclib and ribociclib significantly improved overall survival, whereas palbociclib did not reach statistical significance, and data for dalpiciclib remain immature.

Implications of all the available evidence

Collectively, these findings confirm that CDK4/6 inhibitors plus endocrine therapy represent the standard of care for hormone receptor-positive, HER2-negative advanced breast cancer, providing meaningful improvements in both disease control and overall survival. The consistent benefits across key clinical subgroups support the broad applicability of these agents. Importantly, our data confirm differences in long-term survival effects among individual CDK4/6 inhibitors. Guideline recommendations might benefit from acknowledging ribociclib and abemaciclib as preferred first-line options, given their observed overall survival benefits, whereas palbociclib could be used primarily for disease control or when other agents are less suitable. Future research should focus on head-to-head comparative trials, identifying biomarkers of response and resistance, clarifying optimal treatment sequencing strategies, and evaluating patient-reported outcomes and toxicity profiles to refine individualised care.

Source: The Lancet Oncology