Implementation Study to Describe and Compare Retention Rate and Adherence to Adjuvant Therapy With Ribociclib With and Without Usage of Mobile Application in Patients With HR+ HER2-negative Stage II and III Breast Cancer in Real-world Practice

This study is comparing whether using a mobile app alongside standard hormone-blocking treatment (ribociclib plus aromatase inhibitor) helps people with hormone-receptor-positive, HER2-negative breast cancer stay on their medications longer and adhere more consistently. **You may be eligible if...** - You have been diagnosed with stage II or III hormone-receptor-positive, HER2-negative breast cancer - You have had curative surgery for your cancer - You are 18 or older - You have been prescribed ribociclib within the past 28 days or are about to start it - You can provide written informed consent **You may NOT be eligible if...** - You are currently enrolled in another interventional clinical trial - You are receiving treatment for a different active cancer at the time of enrollment Talk to your doctor to see if this trial is right for you.