The impact of palbociclib/paclitaxel combinations on glucose metabolism may be relevant in the clinic, considering that 18F-FDG PET/CT, largely used for both cancer staging and assessment of response to chemotherapy, has recently emerged as an useful tool for monitoring the response to palbociclib in ER-positive and HER2-negative metastatic BC patients, especially to select the patients with no clinical benefit34. This evidence concerns the gene ESR1 and breast cancer.