[Ondansetron in the prevention of radiation-induced nausea and emesis in patients treated with single-fraction irradiation].

INTRODUCTION

Intensity and severity of radiation-induced nausea and emesis depend on a number of factors including irradiation site, irradiation dose, treatment field (width and length), and age of the patients. Although less intensive than that induced by chemotherapy, during protracted courses of fractionated radiotherapy discomfort can be substantial. As early as 1953, Court-Brown [2] described characteristic symptoms after a single-fraction radiotherapy as "acute irradiation syndrome": irradiation was followed by asymptomatic period of 40-90 minutes, after that the patient experienced an acute episode of emesis, usually without preceding nausea. After a period of relative stabilization, additional episodes of emesis occurred for six hours after irradiation, decreasing its intensity with time. Danjoux et al. [5] noted a higher incidence of radiation-induced emesis after the upper half-body irradiation (UHBI) than after the lower half-body irradiation (LHBI), lack of efficacy of antiemetics administered, and similar response to emesis after the lower or the upper half-body irradiation. These results suggested that critical area was the upper abdomen. Although the exact mechanism of occurrence of radiation-induced emesis is still unknown, recent studies revealed that serotonin released from the gastrointestinal tract also produced emesis through mechanisms of involvement of 5-hydroxytriptamines (5-HT3) receptors, visceral afferent fibers and chemoreceptor trigger zone. We have, therefore, used a new 5-HT3 antagonist, ondansetron, in prevention of radiation-induced emesis in patients treated with single-fraction radiotherapy.

MATERIAL AND METHODS

All patients included in the study had bone metastases treated for pain relief and in all of them, the entire or a part of the upper abdomen was enclosed in the treatment field. The patients' characteristics are given in Table 1. Patients in group I had vertebral lesions that required the central radiation field at Th8-L3 level. Patients in group II were treated with LHBI-the upper field border at crista illiaca; those in group III with UHBI-the lower field border at umbilicus, while those treated with mid-half-body irradiation had the lower field border at the floor of the pelvis. Patients in group I received 8 mg of ondansetron orally, three times a day, for 3-5 days after irradiation. Those in groups II-IV received 0.15 mg/kg of ondansetron intravenously 15 minutes before HBI, just on the day of irradiation. To verify patients' data we used a special questionnaire. Emetic episodes were defined as every emetic episode with minimal interval of 1 minute between separate episodes. Response to therapy was considered complete (no episodes within 24 hours), major response (with only 1-2 episodes), minor (3-5 episodes) and no response (more than 5 episodes of emesis or administration of additional new antiemetics).

RESULTS

In group I, 93% of patients had complete response within 24 hours, while 7% had major response of emesis. Regarding nausea, 89% had complete lack of nausea, while 11% had moderate nausea. In the next 5 days, 96-100% of patients had complete response or major response. At the same time, nausea was controlled in more than 80% of patients. In group II, there was a 100% response rate regarding nausea and emesis lasting for 5 days after radiation therapy. Patients in groups III and IV had also a 100% response rate regarding both nausea and vomiting. Side-effects of ondansetron administration were not observed.

DISCUSSION

The results of this pilot study showed the excellent effect of the new 5-HT3 antagonist, ondansteron, in prevention of radiation-induced nausea and emesis. They confirmed results of the other authors [9, 10, 11] that used this antiemetic in the control of radiation-induced emesis. These studies included a variety of radiotherapeutic time-dose fractionation schedules, and some of them [11] included results of the total body irradiation. (ABSTRACT TRUN