In the multivariate analysis for grade ≥ 3 neutropenia, ribociclib use (OR: 0.46, 95% CI: 0.25–0.84, p = 0.011), aromatase inhibitor therapy (OR: 0.51, 95% CI: 0.27–0.96, p = 0.048), and higher LUC levels (OR: 0.49, 95% CI: 0.27–0.88, p = 0.017) were independently associated with a lower risk of developing grade ≥ 3 neutropenia (Table 5). Here, CYP19A1 is linked to neutropenia.