Abemaciclib plus endocrine therapy in high-risk, node-positive early breast cancer in Italian practice: interim analysis of prospective observational IT-PATH study

Background Abemaciclib plus endocrine therapy (ET) is an established adjuvant treatment for hormone receptor (HR)-positive, human epidermal growth factor receptor 2 (HER2)-negative, node-positive, high-risk early breast cancer (EBC), based on monarchE trial. Prospective real-world data on persistence, adherence, dose management, and patient-reported outcomes (PROs) remain lacking. IT-PATH was designed to address these gaps. Methods IT-PATH is a prospective, multicenter, noninterventional study enrolling patients with HR-positive, HER2-negative high-risk EBC treated with adjuvant abemaciclib + ET at 18 Italian sites. This preplanned interim analysis reports data from the first 100 patients reaching 6-month follow-up. Primary outcome: 6-month treatment persistence and discontinuation rate. Secondary outcomes: adherence [modified medication possession ratio (mMPR)], dose management, safety. Exploratory endpoints (PROs): health-related quality of life (HRQoL), sexual health, and work productivity. Results Patients were 100% female, with a mean age of 55.4 years; 89.6% had Eastern Cooperative Oncology Group Performance Status 0. Treatment persistence at 3 months was 100% and at 6 months was 98% (median follow-up, 5.6 months). Discontinuation occurred in 2% due to adverse events (AEs). Reductions occurred in 52%; high adherence (mMPR ≥0.8 in 89.8%). AEs ≥ grade 3 were reported in 29% (no grade 4/5). Diarrhea (85%), asthenia (38%), and neutropenia (34%) were the most frequent AEs (any grade). No clinically meaningful changes from baseline were observed across all PROs. Conclusions This interim analysis provides prospective real-world evidence that, in routine clinical practice, adjuvant abemaciclib + ET demonstrates feasibility and manageable tolerability with high treatment persistence and no clinically meaningful changes in HRQoL during the first 6 months of therapy. These findings support the value of proactive and personalized dose management to sustain treatment exposure and patient well-being.