In the two phase 3 trials of palbociclib, grade 3/4 ALT elevations occurred in 2% of the palbociclib group (19/789 patients with advanced breast cancer) with no grade 3/4 ALT elevations (0/394) in the comparator (endocrine monotherapy) group (p = 0.001) [1], despite the fact that baseline liver metastases were somewhat more common in the comparator group [22]. This evidence concerns the gene GPT and breast cancer.