Olanzapine as Antiemetic Prophylaxis in Moderately Emetogenic Chemotherapy: A Phase 3 Randomized Clinical Trial.

Importance: The role of olanzapine has not been adequately evaluated in moderately emetogenic chemotherapy (MEC) regimens with or without neurokinin-1 receptor antagonists. Objective: To evaluate whether addition of olanzapine to an MEC regimen reduces nausea, vomiting, and use of nausea rescue medications among patients with solid malignant tumors. Design, Setting, and Participants: This multicenter, open-label phase 3 randomized clinical trial included patients aged 18 years or older with solid malignant tumors who were receiving oxaliplatin-, carboplatin-, or irinotecan-based chemotherapy. The trial was conducted at 3 institutes in India from March 26, 2019, to August 26, 2023; the final cutoff date for analysis was September 10, 2023. Exposure: Patients were randomized 1:1 to dexamethasone, aprepitant, and palonosetron with olanzapine (experimental group) or without olanzapine (observation group). The experimental group received 10 mg of olanzapine orally once at night on days 1 through 3 of the chemotherapy regimen. Main Outcomes and Measures: The primary end point was complete response (CR), defined as the proportion of patients with no vomiting, no significant nausea (scored as <5 on a visual analog scale of 1 to 100), and no use of rescue medications for nausea. Secondary end points included the proportion of patients experiencing nausea and chemotherapy-induced nausea and vomiting (CINV), receiving rescue medications, and experiencing adverse events. Results: A total of 560 patients (259 [64%] male; median age, 51 years [range, 19-80 years]) were randomized. The analysis included 544 patients with evaluable data (274 assigned to olanzapine and 270 to observation). Baseline characteristics were evenly matched between the 2 groups. The proportion of patients with CR was significantly greater in the group with (248 [91%]) than without (222 [82%]) olanzapine in the overall 120-hour treatment period (P = .005). Likewise, there were significant differences between the olanzapine and observation groups for nausea control (264 [96%] vs 234 [87%]; P < .001) and CINV (262 [96%] vs 245 [91%]; P = .02) during the overall assessment period, and the proportion of patients receiving rescue medications significantly increased in the observation group (30 [11%]) compared with the olanzapine group (11 [4%]) (P = .001). Grade 1 somnolence was reported by 27 patients (10%) following administration of chemotherapy and olanzapine and by no patients in the observation group. Conclusions and Relevance: In this randomized clinical trial, the addition of olanzapine significantly improved CR rates as well as nausea and vomiting prevention rates in chemotherapy-naive patients who were receiving MEC regimens containing oxaliplatin, carboplatin, or irinotecan. These findings suggest that use of olanzapine should be considered as one of the standards of care in these chemotherapy regimens. Trial Registration: Clinical Trials Registry-India (CTRI) Identifier: CTRI/2018/12/016643.