DV was treated with palliative chemotherapy and entered into the Efficacy and Safety of Palbociclib in Combination With Fulvestrant or Letrozole in Patients With HER2 Negative, ER+ Metastatic Breast Cancer (PARSIFAL) trial [7] in July 2017, where she was randomised to the palbociclib and letrozole arm. This evidence concerns the gene ERBB2 and breast cancer.