Introduction

Palliative radiotherapy aims to reduce symptoms, but not achieve cure, and results in pain relief in 60–80% of patients, ^{Reference Chow, Zeng, Salvo, Dennis, Tsao and Lutz1} with one-third of those with bone metastases experiencing complete relief of pain. ^{Reference Ejima, Ishihara, Miyawaki and Onal2} Single fields (one beam delivering the whole prescription) or parallel opposed pairs (two beams along the same axis) are widely used to deliver palliative radiotherapy, as they are quicker to position and plan, meaning patients spend less time on the treatment couch and there is less of a wait for treatment. The large volume of healthy tissue irradiated ^{Reference Jones and Simone3,Reference Maranzano, De Angelis and Pergolizzi4} coupled with high doses per fraction (8 Gy per fraction or 20 Gy in 5 fractions) for bone metastases ⁵ radiotherapy-induced nausea and vomiting (RINV) is a common side effect of palliative radiotherapy to the upper abdomen, as it causes swelling of the epithelial and stromal tissue. ^{Reference Maranzano, De Angelis and Pergolizzi4,Reference McKenzie, Zaki and Raman6–Reference Enblom, Bergius, Steineck, Hammar and Börjeson8} Patients may also experience side effects such as pain flare and others depending on the site; however, the focus of this study is on RINV. Nausea and vomiting can either occur in an acute phase within 24 hours of the treatment or in a delayed phase up to 10 days after radiotherapy, ^{Reference Feyer, Maranzano, Molassiotis, Roila, Clark-Snow and Jordan9} this study was focussed on the acute phase. Evidence ^{Reference i Garau, Calduch and López10} demonstrates 100% incidence of ‘very severe’ vomiting in patients receiving 6–8 Gy, with an onset of less than 30 minutes after exposure. Patients receiving 4–6 Gy also experienced a 100% incidence, yet the vomiting was ‘severe’ and the onset was under an hour. Some individual-level, patient-related risk factors for RINV have been suggested, such as patient age, sex, previous alcohol use and previous experiences of nausea and vomiting. ^{Reference McKenzie, Zaki and Raman6} Nonetheless, evidence for this is limited and international guidelines ^{Reference Feyer, Maranzano, Molassiotis, Roila, Clark-Snow and Jordan9} only cite concomitant chemotherapy as an individual risk factor. Research has shown that field sizes over 400 cm² significantly increased the risk of RINV. ^{Reference Maranzano, De Angelis and Pergolizzi4} Despite this, current guidelines/or local practice do not specify a field size threshold for which an anti-emetic is considered. Table 1 summarises the current tumour sites deemed to be at high or moderate risk.

Table 1. Emetogenic risk for treatment sites ^{Reference Feyer, Maranzano, Molassiotis, Roila, Clark-Snow and Jordan9}

Single fraction (SF), palliative radiotherapy to some sites is particularly associated with a high or moderate risk of causing RINV, and it is common practice to prescribe these patients prophylactic antiemetic medication before treatment. Published evidence suggests, however, that protocols and practice vary considerably between clinical sites. Evidence indicates that between 50 and 80% of patients receiving radiotherapy suffer from RINV. ^{Reference Feyer, Maranzano, Molassiotis, Roila, Clark-Snow and Jordan9} Despite this, antiemetics are only given to a small number of patients, with a 2010 study ^{Reference Maranzano, De Angelis and Pergolizzi4} reporting that 17% of patients receiving radiotherapy were prescribed antiemetics and only 12·4% prophylactically. Due to the high number of patients experiencing RINV and the negative impact on the patient’s quality of life (QOL), ^{Reference Yee, Drost, Zhang and Wan11} it is imperative that the importance of sufficient prophylactic treatment is recognised. Inadequately controlled nausea and vomiting can cause patients to delay or refuse subsequent treatment, therefore affecting treatment outcomes. ^{Reference Feyer, Maranzano, Molassiotis, Roila, Clark-Snow and Jordan9} Additional impact on patient’s QOL ^{Reference Pirri, Bayliss and Trotter12} arises from the resulting negative impact on social functioning and sleep and an increase in cancer distress.

Published guidelines ^{Reference Roila, Molassiotis and Herrstedt13} can help staff decide whether a patient requires an antiemetic, with the literature recommending a range of 5-HT3 receptor antagonists as appropriate for the control of RINV. ^{Reference Ettinger, Armstrong and Barbour14–Reference Ruhlmann, Jahn and Jordan16} Other antiemetics (outlined in Table 2) are also available and may be used by other centres. It has also been suggested that these patients could be offered proton pump inhibitors or H2 blocker therapy along with the patient eating smaller and more frequent meals instead of larger ones before treatment. ^{Reference Koontz7} Treatments with a high emetogenic risk may also indicate concurrent use of dexamethasone to achieve control. ^{Reference Ettinger, Armstrong and Barbour14} Unfortunately, research around RINV is limited and much less common than that on chemotherapy-induced nausea and vomiting (CINV). Despite the findings in this limited evidence, there is little clarity on which patients should receive medication. Research has shown under half of qualified consultants are aware of antiemetic guidance, ^{Reference Dennis, Zhang and Lutz17} and therefore, the following audit was performed at a major clinical department in order to measure adherence to the prescription of prophylactic antiemetics protocol. The aim of the audit was to assess the extent to which prophylactic antiemetics are being prescribed to patients who are receiving SF radiotherapy to an area classed as a high or moderate emetogenic risk.

Table 2. Types of antiemetic that can be used for RINV ^{Reference Ettinger, Armstrong and Barbour14,Reference Andrews and Sanger18,19}