Radiation-induced emesis: a problem with many open questions.

Abstract

Radiation-induced emesis (RIE) is often considered to be less frequent and less severe than nausea/vomiting encountered in patients receiving chemotherapy, although the issue has only been addressed in a few studies. It is possible that radiation oncologists undervalue the clinical relevance of RIE. If untreated, sickness produces an adverse effect on the patient's quality of life and may cause interruption of the treatment with possible unfavorable effects on tumor control. A prospective observational trial on RIE has recently been published by the Italian Group for Antiemetic Research in Radiotherapy (IGARR). The study evidenced that the overall cumulative incidence of vomiting and nausea occurred in about 40% of patients undergoing radiotherapy, and that the irradiated site, radiation field size, and previous chemotherapy were significant risk factors. Patients submitted to abdominal radiotherapy were at major risk of vomiting and nausea (71%), followed by those treated on the thorax, brain, head and neck, and pelvis (49%, 40%, 40%%, and 39%, respectively). Few small randomized clinical trials have evaluated the efficacy of various antiemetic drugs in preventing RIE. Generally, patients who entered these trials were those submitted to total body irradiation, half body irradiation or upper abdomen irradiation because of the greater risk of developing nausea and/or vomiting. The few controlled trials published have shown that dopamine receptor antagonists were effective in only about 50% of patients, whereas 5-hydroxytryptamine antagonists were more effective. Clinical practice guidelines for the use of antiemetics have recently been published by MASCC (Multinational Association of Supportive Care in Cancer) and ASCO (American Society of Clinical Oncology). Unfortunately, their recommendations were quite different, when classifying radiation emetogenic risk categories and when giving indications for the use of antiemetic drugs. However, MASCC and ASCO recommendations both suggested a prophylaxis with a 5-hydroxytryptamine antagonist and a corticosteroid for patients submitted to high emetogenic radiotherapy. There is evidence about the effectiveness of oral dexamethasone alone in fractionated upper abdomen radiotherapy and the use of a rescue antiemetic treatment as a possible alternative to the prophylaxis. Many questions remain open, and other prospective controlled trials on RIE are needed to answer them. Considering that radiotherapy to the abdomen, pelvis and thorax presents the most frequent problems in radiation oncology clinical practice, future trials on RIE should deal with these irradiated sites. The IGARR is carrying out a double-blind randomized clinical trial comparing prophylactic ondansetron plus dexamethasone versus ondansetron and dexamethasone given as a rescue treatment in patients undergoing fractionated radiotherapy to the upper abdomen.