Abstract P4-01-01: RIBANNA 5th interim analysis: Matched-pair analysis of progression-free survival (PFS) across treatment cohorts and comparison of frontline ribociclib + endocrine therapy PFS data from RIBANNA vs MONALEESA trials, in HR+, HER2– ABC

Abstract Background: Ribociclib (RIB) plus endocrine therapy (ET) has demonstrated a statistically significant survival benefit across the three phase 3 MONALEESA (ML) trials, irrespective of menopausal status, line of therapy, or combination partner. RIBANNA (CLEE011ADE03), a prospective, noninterventional study assessing the efficacy and safety of RIB + ET, or ET monotherapy or chemotherapy (CT) in first-line (1L) setting in pre-, peri- and postmenopausal patients (pts) with hormone receptor–positive (HR+), human epidermal growth factor receptor-2–negative (HER2–) advanced breast cancer (ABC) is ongoing in Germany since October 2017 to gain insights into real-world scenario. In the 5th interim analysis (IA) from RIBANNA, a matched-pair analysis of 1L PFS data from the three treatment cohorts and comparison of 1L PFS data on RIB + ET from RIBANNA versus (vs) ML trials will be performed. Methods: Pre-, peri- and postmenopausal women receiving RIB + ET, ET monotherapy, or CT as 1L treatments for HR+, HER2– ABC, in accordance with German treatment guidelines, were included. Propensity score matched (PSM) analysis of PFS data from the 3 treatment cohorts will be conducted to reduce the bias due to confounding variables. In addition to safety analyses, comparison of 1L PFS data on RIB + ET from RIBANNA vs ML trials will be performed. Results: By the cutoff date of the 4th IA (October 11, 2021), data were available for 2187 pts, including 1849 (83.0%), 193 (78.1%), and 145 (73.6%) pts from the RIB + ET, ET monotherapy, and CT cohorts in 1L setting, respectively (Table 1). Of these 2187 pts, 1111 postmenopausal pts received 1L RIB + letrozole; 357 postmenopausal pts received 1L RIB + fulvestrant, and 158 pre- and perimenopausal pts received 1L RIB + anastrazole/letrozole. The unadjusted Kaplan–Meïer estimate for median PFS was 31.7 months (95% confidence interval [CI], 28.5–36.2) in the RIB + ET cohort, 25.7 months (95% CI, 18.0–not reached) in the ET monotherapy cohort, and 15.3 months (95% CI, 9.5–17.5) in the CT cohort. The most frequent treatment-emergent adverse events (grade 3 or 4) in the RIB + ET and ET monotherapy cohorts were neutropenia (14.8% and 6.6%, respectively) while that in CT cohort was general physical health deterioration (9.1%). Conclusions: In RIBANNA, a diverse pt population is being analyzed in a real-world setting; treatment with RIB + ET has been observed to be well adopted. The 5th IA is planned in October 2022 and data will be presented in SABCS 2022, which will include PSM analysis to compare 1L PFS data across treatment cohorts as well as comparison of 1L PFS data on RIB + ET from RIBANNA vs ML trials. The safety profile of RIB was found to be similar to those observed in ML trials. Table 1. Patient demographics and baseline clinical characteristics from the 4th IA. Citation Format: Christian Jackisch, Cosima Brucker, Thomas Decker, Anne Engel, Peter A. Fasching, Thomas Göhler, Jan Janssen, Andreas Köhler, Kerstin Lüdtke-Heckenkamp, Diana Lüftner, Marion van Mackelenbergh, Frederik Marmé, Arnd Nusch, Beate Rautenberg, Toralf Reimer, Marcus Schmidt, Rudolf Weide, Pauline Wimberger, Christian Roos, Achim Wöckel. RIBANNA 5th interim analysis: Matched-pair analysis of progression-free survival (PFS) across treatment cohorts and comparison of frontline ribociclib + endocrine therapy PFS data from RIBANNA vs MONALEESA trials, in HR+, HER2– ABC [abstract]. In: Proceedings of the 2022 San Antonio Breast Cancer Symposium; 2022 Dec 6-10; San Antonio, TX. Philadelphia (PA): AACR; Cancer Res 2023;83(5 Suppl):Abstract nr P4-01-01.