Background: Neutropenia is a potentially serious side effect of chemotherapy and a major risk factor for infections, which can be life-threatening. It has been hypothesised that a low bacterial diet (LBD) can prevent the occurrence of infections and (infection-related) mortality in cancer patients receiving chemotherapy causing episodes of neutropenia, but much remains unclear.
Objectives: The primary objective was to determine the efficacy of an LBD versus a control diet in preventing the occurrence of infection and to decrease (infection-related) mortality in adult and paediatric cancer patients receiving chemotherapy causing episodes of neutropenia. Secondary objectives were to assess the time to first febrile episode, the need for empirical antibiotic therapy, diet acceptability and quality of life.
Search methods: We searched the following electronic databases: the Cochrane Central Register of Controlled Trials (CENTRAL) (The Cochrane Library, issue 3 2011), Database of Abstracts of Reviews of Effects (DARE) (The Cochrane Library, issue 3 2011), PubMed (from 1946 to 20 October 2011), EMBASE (from 1980 to 20 October 2011) and CINAHL (from 1981 to 20 October 2011). In addition, we searched several conference proceedings (from 2000 to either 2010 or 2011) and reference lists of relevant articles. To identify ongoing trials we contacted researchers working on this topic and we scanned the National Institute of Health Register and the ISRCTN Register (www.controlled-trials.com; searched May 2012).
Selection criteria: Randomised controlled trials (RCTs) comparing the use of an LBD with a control diet with regard to infection rate, (infection-related) mortality, time to first febrile episode, need for empirical antibiotic therapy, diet acceptability, and quality of life in adult and paediatric cancer patients receiving chemotherapy causing episodes of neutropenia.
Data collection and analysis: Two review authors independently performed the study selection, 'Risk of bias' assessment and data extraction. Analyses were performed according to the guidelines of the Cochrane Handbook for Systematic Reviews of Interventions.
Main results: We identified three RCTs assessing different intervention and control diets in 192 patients (97 randomised to intervention diet; 95 to control diet) with different types of malignancies. Co-interventions (e.g. protective environment, antimicrobial prophylaxis, central venous catheter care, oral care, hygiene practices and colony-stimulating factors) and outcome definitions also differed between studies. In all included studies it was standard policy to give empirical antibiotics (and sometimes also antimycotics) to (some of) the patients diagnosed with an infection. Two studies included adults and one study included children. In all studies only a scant description of treatment regimens was provided. All studies had methodological limitations. Pooling of results of included studies was not possible. In two individual studies no statistically significant difference in infection rate between the intervention and control diet was identified; another study showed no significant difference in the number of chemotherapy cycles with an infection between the treatment groups. None of the studies mentioned infection-related mortality, but in one study no significant difference in overall survival between the treatment groups was observed. Time from onset of neutropenia to fever, the duration of empirical antibiotics and antimycotics, diet acceptability (i.e. following the diet easily and following the diet throughout all chemotherapy cycles) and quality of life were all evaluated by only one study; for all outcomes no statistically significant differences between the treatment arms was observed.
Authors' conclusions: At the moment there is no evidence from individual RCTs in children and adults with different malignancies that underscores the use of an LBD for the prevention of infection and related outcomes. All studies differed with regard to co-interventions, outcome definitions, and intervention and control diets. Since pooling of results was not possible and all studies had serious methodological limitations, no definitive conclusions can be made. It should be noted that 'no evidence of effect', as identified in this review, is not the same as 'evidence of no effect'. Based on the currently available evidence, we are not able to give recommendations for clinical practice. More high-quality research is needed.