Radiation-induced emesis: effects of ondansetron.

The incidence, severity, and onset of radiation-induced emesis (RIE) are related to field size, site, and dose per fraction. Radiation-induced emesis can occur (1) within 2 to 3 weeks in approximately 50% of patients after conventional fractionated radiotherapy (200 cGy/fraction) to the upper abdomen, (2) acutely in more than 90% of patients receiving fractionated total body irradiation (TBI) for bone marrow transplantation, and (3) within 30 to 60 minutes in more than 80% of patients following single high-dose (> 500 cGy)/large field hemibody irradiation (HBI). The increased frequency of emesis associated with TBI and HBI has renewed the interest in the mechanism and treatment of RIE. A number of studies have reported a significant difference in the incidence of emesis following doses of > or = 500 cGy to the upper-mid (> 80%) and lower (20% to 40%) hemibody. The data suggested that the organ responsible for emetic response was in the upper abdomen. However, the mechanism of RIE is not well understood, although degradation products from normal tissues and tumor have been suggested. The introduction and effectiveness of the 5-hydroxytryptamine3 receptor antagonists in chemotherapy-induced emesis and the location of these receptors in the upper abdomen (possible site of the radiation-associated emetic response) suggested that this group of compounds may have a role in RIE. Lucraft and Palmer (Clin Radiol 33:621-622, 1982) reported no differences between levonantradol and chlorpromazine in preventing RIE in patients treated with single doses of more than 10 Gy to a small upper abdominal field. Priestman (Eur J Cancer Clin Oncol 25:529-533, 1989 [Suppl]) reported on a pilot and randomized study with ondansetron after single doses of 8 to 10 Gy to the upper abdomen. In the pilot study, ondansetron achieved major or complete control of vomiting in 77% to 90% of patients; subsequently, he reported a significant difference between ondansetron (97%) and metoclopramide (45%) in controlling RIE on the day of radiotherapy. Hewitt et al (Bone Marrow Transpl 7:431-433, 1991) reported a complete or major response on 93% of the days of ondansetron therapy during pretreatment therapy with cyclophosphamide and TBI for bone marrow transplantation. A preliminary analysis of 41 patients treated with HBI at the Rex Cancer Center confirms the role of ondansetron in RIE. Twenty-eight patients (upper-mid 16 patients/lower HBI 12 patients) did not receive pretreatment antiemetics (group A); seven received non-ondansetron pre-HBI (group B); and six received ondansetron (group C).(ABSTRACT TRUNCATED AT 400 WORDS)