Efficacy of Olanzapine for Prophylaxis of Delayed Chemotherapy-Induced Nausea and Vomiting in Patients with Breast Cancer Receiving Dose-Dense AC with a Steroid-sparing Regimen: A Single-Center Pilot Study

Purpose This study examined the feasibility of a steroid-sparing approach in a dose-dense AC regimen in breast cancer patients, while integrating olanzapine to manage chemotherapy-induced nausea and vomiting (CINV). Methods A prospective, single-center study was conducted with 30 patients diagnosed with Stage I–III breast cancer who underwent treatment with a dose-dense AC regimen. Patients were given prophylactic olanzapine from days 1 to 4 along with the standard three-drug combination antiemetic regimen, excluding dexamethasone on days 2 and 3. Nausea, vomiting, and drowsiness were evaluated using a validated 4-point Likert scale. The main outcome measured was the complete response (CR) rate in the delayed phase. Results The CR rates were 73% and 63% in the acute and delayed phases, respectively. The total control and complete control rates in the acute phase were 60% and 73%, respectively, while in the delayed phase, they were 36.6% and 63%. Moderate-to-severe daytime sleepiness was observed in 40% of the patients. The mean nausea score on the EORTC QLQ-C30 remained within the minimal important difference threshold for all four treatment cycles. Conclusion This study suggests that olanzapine administration enables steroid reduction without compromising CINV control in patients receiving dose-dense AC. A steroid-sparing regimen may mitigate steroid-related adverse effects while maintaining antiemetic efficacy. Further large-scale studies are warranted to validate these findings and optimize steroid-sparing strategies in antiemetic protocols.