The cognitive debriefing results for the NFBSI-16 and PROMIS Physical Function Short Form 10b demonstrated that HR+/HER2- advanced breast cancer patients were able to complete and comprehend the questionnaires in ways consistent with developer and researcher expectations, and that overall, the concepts covered by the questionnaires are relevant to the patient experience of HR+/ HER2- advanced breast cancer. This evidence concerns the gene ERBB2 and breast cancer.