A. They inhibit cyclin D1 overexpression. B. They inhibit p16 overexpression. C. They inhibit the cell cycle at the G1/S transition. D. They promote the formation of the Rb-E₂F complex.

A. To provide a treatment option for patients who develop resistance to endocrine therapy B. To provide a treatment option for patients who are intolerant to endocrine therapy adverse events C. To improve patients' tumor biomarker profiles D. To reverse patients' disease progression

A. The most common adverse event in all 3 agents was neutropenia, which occurred in about 80% of patients. B. The hazard ratios for progression-free survival (PFS) were 50% higher in the studies of second-line therapies than in the studies of first-line therapies. C. All of the women in these studies were postmenopausal. D. In the studies of second-line therapy, both abemaciclib and palbociclib increased PFS significantly compared with fulvestrant alone.

A. Stop the palbociclib and letrozole and switch to another CDK 4/6 inhibitor. B. Reduce her dose of palbociclib to 100 mg daily immediately and reassess her ANC on Day 1 of her next treatment cycle. C. Continue palbociclib to complete 21 days and continue to monitor her for fever or other signs/symptoms of infection. D. Hold the palbociclib until her ANC returns to normal and resume at the next lower dose (100 mg) in the next cycle.