Introduction: Olanzapine (OLZ) effectively reduces chemotherapy-induced nausea and vomiting (CINV), but standard doses can cause drowsiness.This study compared the efficacy and safety of low-dose vs standard-dose OLZ in breast cancer patients undergoing highly emetogenic chemotherapy (HEC).Materials and methods: This prospective observational study was conducted at a single center, where all patients received standard antiemetic therapy.Patients were randomly assigned to receive oral OLZ at doses of 2.5, 5, or 10 mg nightly on days 1-4 of each chemotherapy cycle.Primary endpoints included the rates of complete response (CR), complete control (CC), and total control (TC) during the acute phase (AP), delayed phase (DP), and overall phase (OP) of CINV.Secondary outcomes included quality of life (QoL)-related to emesis and assessment of adverse effects.Results: Between November 2022 and November 2023, 220 patients were screened, with 204 enrolled (68 in each treatment arm).The 5 mg OLZ dosage showed the highest rates of CR, CC, and tolerability (TC).The CR and CC rates were similar for the 2.5 and 10 mg groups, but the TC rate was better in the 10 mg group.The 5 mg OLZ achieved CR and CC rates of 94.1%, with TC rates of 86.8% in the acute and dependent phases, and 85.3% in the ongoing phase.Rescue medication use was lowest in the 5 mg group at 4.4%, compared with 7.4% in the 2.5 mg group and 10.3% in the 10 mg group.Additionally, 97.1% of patients in the 5 mg group reported improved QoL Functional Living Index Emesis (FLIE) score >108, compared with 92.6 and 89.7% in the other groups.Drowsiness (25%) and tiredness (38.2%) were the most noted adverse effects.Conclusion: Olanzapine is a well-tolerated antiemetic prophylactic when combined with standard therapies.The 5 mg dosage demonstrated superior response rates, while the 2.5 mg dosage was equally effective with less toxicity than the 10 mg dosage.
Verma et al. (Mon,) studied this question.