Relevance Rating: High
- This study describes a clinical trial on a combined therapy for metastatic breast cancer. It is directly relevant for metastatic breast cancer patients.
- It is currently clinically applicable. Palbociclib is currently approved for use with fulvestrant, based on the improvement in progression-free survival time (which has been previously reported). While overall survival was not increased, improvement in progression-free survival was significant.
- This treatment approach is useful for people with advanced or metastatic breast cancer that is ER-positive and HER2-negative who have progressed on previous endocrine therapy. The time until disease progression has been shown to be significantly longer with the addition of palbociclib to fulvestrant.
Scientific Strength: Medium-High
- This is a well-controlled prospective, randomized, double-blinded, placebo-controlled study.
- The intervention, treatment with either palbociclib and fulvestrant or placebo and fulvestrant, is clearly described.
- The analysis is sound and conclusions are justified. The authors of this study provide context for their results and interpretation.
- Although the number of participants in the study was sufficient to determine progression-free survival (its primary aim as published previously), this trial may have too few participants to address overall survival (OS), particularly in some of the stratified groups, a secondary aim of the study. This is the largest limitation of this study; it led to several questions about whether or not there are small but meaningful improvements in overall survival with the addition of palbociclib. The authors emphasize the numerical increase in OS, however the lack of statistical significance means that this increase may be due to chance and may not be repeatable (or it may be a true small difference). This study cannot determine which is the case.