The GIM 13-AMBRA project is a longitudinal cohort investigation designed to report on treatment patterns and associated outcome metrics in 939 patients with HER2-negative metastatic breast cancer (MBC). In both Luminal (30.2%) and TNBC (33.3%) groups, first-line care most often involved taxane-based therapy, either alone or with targeted agents—most commonly Bevacizumab. The median PFS1 reached 12.5 months (95% CI 16.79-19.64), showing no subtype-related differences. In contrast, the median TTC1 was markedly shorter in the TNBC cohort (7.7 months, 95% CI 5.7-9.2) compared with Luminal A (13.2 months, 95% CI 11.7-15.1) and Luminal B (11.8 months, 95% CI 10.3-12.8). PFS2 was also reduced in TNBC (5.5 months, 95% CI 4.3-6.5) versus Luminal A (9.4 months, 95% CI 8.1-10.7) and Luminal B (7.7 months, 95% CI 6.8-8.2; F-ratio 4.30, p = 0.014). TTC2 followed the same pattern, with shorter intervals observed in TNBC. Median OS1 for Luminal A patients was 35.2 months (95% CI 30.8-37.4), surpassing Luminal B (28.9 months, 95% CI 26.2-31.2) and TNBC (18.5 months, 95% CI 16-20.1; F-ratio 7.44, p = 0.0006). As one of the most extensive Italian datasets, GIM 13-AMBRA provides valuable real-world evidence concerning timing outcomes across multiple chemotherapy lines in HER2- MBC.
