Background: Olanzapine has been found to have antiemetic properties due to its ability to inhibit multiple serotonergic, dopaminergic, alpha-1 adrenergic and histamine receptors. In 2016, a meta-analysis of 10 randomized controlled trials (RCTs) on olanzapine in the prophylactic setting found olanzapine to be more efficacious than other standard antiemetics in the prophylactic setting. However, since the review, many clinical trials using olanzapine for chemotherapy-induced nausea and vomiting (CINV) have been published-in many cases, contending that further trials would further help elucidate the efficacy of olanzapine for CINV given the continued paucity of literature. The primary aim of this study is to conduct a secondary, cumulative meta-analysis to assess the impact of the most recent trials on the published effect estimate of olanzapine and ultimately determine whether trials published since 2016 have significantly changed the summary estimate.
Methods: As reported previously, a literature search was conducted up until 2015, of Ovid Medline, Embase and the Cochrane Central Register of Controlled Trials; 10 RCTs with a total of over 1,000 patients were included, that compared olanzapine to other antiemetics in the prophylactic setting, which reported on at least one of two endpoints-no emesis and no nausea. The Mantel-Haenszel, random-effects analysis model was used to compute cumulative risk ratios (RR) and their accompanying 95% confidence intervals (CIs).
Results: For the endpoint of emetic control, the cumulative meta-analysis shows that the summary effect did not change noticeably with the inclusion of the most recent trials. In the acute phase, the RR shifted from 1.07 before 2011 to 1.10 after 2015, even after the inclusion of 7 trials. Similar small changes were noted in the delayed and overall phases. For the endpoint of nausea control, the cumulative meta-analysis does show a significant visual change in summary effect, except for nausea control in the acute phase. In the delayed phase, the RR shifts from 1.58 before 2011 to 1.50 after 2015. In the overall phase, the RR shifts from 1.642 before 2011 to 1.53 after 2015.
Conclusions: Olanzapine's efficacy for the prophylaxis of CINV has been sufficiently documented, with respect to emetic control. There is, however, more limited data supporting its efficacy with respect to nausea control.
Keywords: Olanzapine; antiemetic; chemotherapy-induced nausea and vomiting; meta-analysis; prophylaxis.