ASCO issues guidelines on use of antiemetics

The American Society of Clinical Oncology (ASCO) recently issued updated evidence-based practice guidelines for the use of antiemetics in patients who are receiving chemotherapy or radiation. Chemotherapy-induced emesis can negatively affect a patient's quality of life and may have an impact on compliance with future treatments. Approximately 70% to 80% of all cancer patients receiving chemotherapy experience emesis.

The 2006 guidelines serve as updates to the 1999 guidelines and are based on a literature review of published, randomized controlled trials and systematic reviews and meta-analysis of published phase II and III studies. "Since the previous guidelines, new antiemetics have been introduced. The ASCO guidelines better define how to use these new agents," said James Trovato, Pharm.D., MBA, BCOP, associate professor at University of Maryland School of Pharmacy.

The ASCO guidelines recommend the use of a serotonin (5-HT₃) receptor antagonist such as dolasetron (Anzemet, Sanofi-Aventis), granisetron (Kytril, Roche), ondansetron (Zofran, GlaxoSmithKline), palonosetron (Aloxi, MGI PHARMA/Helsinn Healthcare), or tropisetron, dexamethasone, and aprepitant (Emend, Merck) prior to the administration of high emetic risk antineoplastics, which are agents that have a greater than 90% frequency of emesis in the absence of antiemetic prophylaxis. The committee did not select a preferred 5-HT₃ receptor antagonist. Rather, it stated that for the prevention of acute emesis, 5-HT₃ receptor antagonists have equivalent safety and efficacy and can be used interchangeably.

Antineoplastics considered to have a high emetic risk include cisplatin, mechlorethamine (Mustargen, Ovation), streptozocin (Zanosar, Sicor Pharmaceuticals), carmustine (BiCNU, Bristol-Myers Squibb), dacarbazine, dactinomycin (Cosmegen, Ovation), and cyclophosphamide 1500 mg/m² or more. "Using these three agents is appropriate because they have different mechanisms of action and this will allow us to be more successful in controlling nausea and vomiting," stated Trovato.

"The guidelines differ from the previous ones due to the introduction of aprepitant," Trovato said. However, there are still some questions about the use of aprepitant. "For example, can aprepitant be used with lower-risk emetic agents or with low-dose cisplatin?" Aprepitant is an NK1 receptor antagonist that prevents the binding of substance P to the NK1 receptor in the central nervous system.

"The ASCO guidelines also recommend the use of 5-HT₃ receptor antagonists, dexamethasone, and aprepitant in patients receiving an anthracycline in combination with cyclophosphamide-the AC regimen," added Trovato. For patients receiving other moderate emetic risk (30% to 90%) antineoplastics, the committee recommended a combination of a 5-HT₃ receptor antagonist in combination with dexamethasone. This is a recommendation from the 1999 guidelines that has remained unchanged with the exception of patients receiving the AC regimen.

For low emetic potential (10% to 30%) antineoplastics, the committee suggested giving dexamethasone 8 mg, and for minimal emetic risk (<10%) antineoplastics, it is suggested that no antiemetic be routinely administered before chemotherapy. There are no trials that specifically address the optimal antiemetics for low emetic risk chemotherapy. For patients receiving total-body radiation, a 5-HT₃ receptor antagonist is recommended before each fraction of radiation and for at least 24 hours afterwards.