Older patients who took palbociclib plus an aromatase inhibitor lived longer than those who took an aromatase inhibitor alone. Older patients who took palbociclib plus an aromatase inhibitor also lived longer without their cancer getting worse and started chemotherapy later than those who took an aromatase inhibitor alone. These results support using palbociclib plus an aromatase inhibitor as the first treatment for patients aged 75 years or older with HR+/HER2- metastatic breast cancer.