Characteristics, treatment patterns and survival of patients with high-risk early hormone receptor-positive breast cancer in French real-world settings: an exploratory study of the CANTO cohort

Background: Patients with hormone receptor-positive, human epidermal growth factor receptor 2 (HER2)-negative breast cancer (HR+ BC) with unfavorable features have an increased risk of relapse and are currently candidate for additional treatment strategies. We evaluated the real-world clinicopathological characteristics, treatment patterns and survival outcomes of these patients within the CANcer TOxicities study (CANTO, NCT01993498). Patients and methods: This is a retrospective analysis of the prospective data collected within CANTO between 2012 and 2022. Patients with high-risk HR+ BC were defined either by the identification of at least four positive axillary lymph nodes (LNs) or one to three positive axillary LNs with a tumor size ≥5 cm or histologic grade 3 (cohort 1). The definition 1-3 positive LNs with Ki-67 ≥20% was also considered (cohort 2). The Kaplan–Meier method was used for survival analysis. Results: Patients with high-risk HR+ BC represented 15.0%-19.6% of HR+ BC (cohort 1 and 2, respectively) in the CANTO cohort. Of the 1266 patients in cohort 1, 617 patients (49.0%) had ≥4 LNs, 327 (26.0%) had tumor ≥5 cm and 727 (57.6%) had grade III tumors. 79.9% had a favorable Charlson comorbidity score and 88.1% stage II/IIIA. Patients with ≥10 LNs accounted for 11.8%. (Neo)adjuvant chemotherapy was administered in 94.2%. Endocrine therapy was prescribed in 97.3%, mostly with aromatase inhibitors and discontinued in 34.3%, mainly for adverse events. Patients enrolled at least 6 years before data extraction had a 5-year invasive disease-free survival and 5-year distant relapse-free survival of 79.9% [95% confidence interval (CI) 77.2% to 82.4%] and 83.5% (95% CI 80.9% to 85.7%), respectively. Conclusions: This real-world study confirms that patients with HR+ BC and unfavorable clinicopathological features are at risk of relapse early in their adjuvant treatment trajectory, despite (neo)adjuvant chemotherapy. It is imperative to implement innovative treatment approaches for high-risk patients, ideally adding them as early as possible to the adjuvant treatment.