On the basis of the studies described above, palonosetron was approved by the FDA in July 2003 for the prevention of acute N&V associated with initial and repeat courses of moderately and highly emetogenic cancer chemotherapy and for the prevention of delayed N&V associated with initial and repeat courses of moderately emetogenic cancer chemotherapy. One randomized, double-blind, phase III trial compared palonosetron plus dexamethasone with granisetron plus dexamethasone for the prevention of CINV in patients receiving highly emetogenic chemotherapy. Palonosetron was equivalent to granisetron in the acute phase (first 24 hours) and better than granisetron in the delayed phase (24–120 hours), with a comparable safety profile for the two treatments.[Level of evidence: I]
Comparison of agents
Clinicians should note that studies suggest that there are no major differences in efficacy or toxicity of the three first-generation 5-HT3 receptor antagonists (dolasetron, granisetron, and ondansetron) in the treatment of acute CINV. These three agents are equivalent in efficacy and toxicity when used in appropriate doses.;[45,46,47][Level of evidence: I] Although these agents have been shown to be effective in the first 24 hours postchemotherapy (acute phase), they have not been demonstrated to be effective in days 2 to 5 postchemotherapy (delayed phase).[29,48,49]
Palonosetron, the second-generation 5-HT3 receptor antagonist, has been approved for the control of delayed emesis for patients receiving moderately emetogenic chemotherapy.;[Level of evidence: I]
Despite the use of both first-generation and second-generation 5-HT3 receptor antagonists, the control of acute CINV, and especially delayed N&V, is suboptimal, and there is considerable opportunity for improvement with either the addition or substitution of new agents in current regimens.[Level of evidence: II];[Level of evidence: I][48,49]
Substance P Antagonists (NK-1 Receptor Antagonists)
The initial clinical studies using the NK-1 receptor antagonists [51,52,53][Level of evidence: I] demonstrated that the addition of an NK-1 receptor antagonist (CP-122,721, CJ-11,794, MK-0869 [aprepitant]) to a 5-HT3 receptor antagonist plus dexamethasone prior to cisplatin chemotherapy improved the control of acute emesis compared with a 5-HT3 receptor antagonist plus dexamethasone and improved the control of delayed emesis compared with placebo. In addition, as a single agent, aprepitant (MK-0869) had an effect similar to that of ondansetron on cisplatin-induced acute emesis but was superior in the control of delayed emesis. Subsequent studies [55,56][Level of evidence: I] showed that the combination of aprepitant and dexamethasone was similar to a 5-HT3 receptor antagonist plus dexamethasone in controlling acute emesis but was inferior in controlling acute emesis compared with triple therapy (aprepitant, 5-HT3 receptor antagonist, and dexamethasone). These studies also confirmed the improvement of delayed emesis with the use of aprepitant compared with placebo. Two studies [31,57][Level of evidence: I] have also shown an improvement in cisplatin-induced delayed emesis with the combination of aprepitant and dexamethasone compared with dexamethasone alone, with the improvement maintained over repeat cycles of cisplatin chemotherapy.