Adherence and Safety of Ribociclib Plus Aromatase Inhibitors in Patients With Early Stage, HR+ and HER2- Breast Cancer

Breast cancer is the most common malignancy in women, with HR+/HER2- early breast cancer accounting for approximately 70% of cases. Although adjuvant endocrine therapy substantially reduces the risk of recurrence, a clinically meaningful proportion of patients, particularly those with intermediate- and high-risk disease, still experience relapse. The addition of CDK4/6 inhibitors such as ribociclib to endocrine therapy has demonstrated significant improvement in invasive disease-free survival (iDFS) and is now part of standard adjuvant treatment for selected patients. However, the real-world effectiveness of prolonged oral therapy depends heavily on patient adherence, which may be negatively affected by treatment duration, adverse events, and the absence of immediate perceived benefit. Evidence regarding adherence to adjuvant ribociclib therapy in routine clinical practice remains limited. This study therefore aims to evaluate whether a structured adherence-support intervention can improve treatment adherence during ribociclib therapy and to explore the relationship between adherence and long-term clinical outcomes, including iDFS.