Experimental radiotherapy-induced enteritis: a probiotic interventional study

The role of bacteria and its derived biomaterials in cancer radiotherapy

Bacteria-mediated anti-tumor therapy has received widespread attention due to its natural tumor-targeting ability and specific immune-activation characteristics. It has made significant progress in breaking the limitations of monotherapy and effectively eradicating tumors, especially when combined with traditional therapy, such as radiotherapy. According to their different biological characteristics, bacteria and their derivatives can not only improve the sensitivity of tumor radiotherapy but also protect normal tissues. Moreover, genetically engineered bacteria and bacteria-based biomaterials have further expanded the scope of their applications in radiotherapy. In this review, we have summarized relevant researches on the application of bacteria and its derivatives in radiotherapy in recent years, expounding that the bacteria, bacterial derivatives and bacteria-based biomaterials can not only directly enhance radiotherapy but also improve the anti-tumor effect by improving the tumor microenvironment (TME) and immune effects. Furthermore, some probiotics can also protect normal tissues and organs such as intestines from radiation via anti-inflammatory, anti-oxidation and apoptosis inhibition. In conclusion, the prospect of bacteria in radiotherapy will be very extensive, but its biological safety and mechanism need to be further evaluated and studied.

Bacteria−Based Synergistic Therapy in the Backdrop of Synthetic Biology

Although the synergistic effect of traditional therapies combined with tumor targeting or immunotherapy can significantly reduce mortality, cancer remains the leading cause of disease related death to date. Limited clinical response rate, drug resistance and off-target effects, to a large extent, impede the ceilings of clinical efficiency. To get out from the dilemmas mentioned, bacterial therapy with a history of more than 150 years regained great concern in recent years. The rise of biological engineering and chemical modification strategies are able to optimize tumor bacterial therapy in highest measure, and meanwhile avoid its inherent drawbacks toward clinical application such as bacteriotoxic effects, weak controllability, and low security. Here, we give an overview of recent studies with regard to bacteria-mediated therapies combined with chemotherapy, radiotherapy, and immunotherapy. And more than that, we review the bacterial detoxification and targeting strategies via biological reprogramming or chemical modification, their applications, and clinical transformation prospects.

Coenzyme Q10 attenuates inflammation and fibrosis implicated in radiation enteropathy through suppression of NF-kB/TGF-β/MMP-9 pathways

Radiation enteropathy is one the most common clinical issue for patients receiving radiotherapy for abdominal/pelvic tumors which severely affect the quality of life of cancer patients due to dysplastic lesions (ischemia, ulcer, or fibrosis) that aggravate the radiation damage. Herein, this study demonstrated the prophylactic role of coenzyme Q10 (CoQ10), a powerful antioxidant, against radiotherapy-induced gastrointestinal injury. Male Sprague Dawley rats were divided into four groups: group 1 was defined as control, and group 2 was the irradiated group. Group 3 and 4 were CoQ10 control and radiation plus CoQ10 groups, respectively. CoQ10 (10 mg/kg) was orally administered for 10 days before 10 Gy whole-body radiation and was continued for 4 days post-irradiation. CoQ10 administration protected rats delivered a lethal dose of ϒ-radiation from changes in crypt-villus structures and promoted regeneration of the intestinal epithelium. CoQ10 attenuated radiation-induced oxidative stress by decreasing lipid peroxidation and increasing the antioxidant enzyme catalase activity and reduced glutathione level. CoQ10 also counteracts inflammatory response mediated after radiation exposure through downregulating intestinal NF-ĸB expression which subsequently decreased the level of inflammatory cytokine IL-6 and the expression of COX-2. Radiation-induced intestinal fibrosis confirmed via Masson's trichrome staining occurred through upregulating transforming growth factor (TGF)-β1 and matrix metalloproteinase (MMP)-9 expression, while CoQ10 administration significantly diminishes these effects which further confirmed the anti-fibrotic property of CoQ10. Therefore, CoQ10 is a promising radioprotector that could prevent intestinal complications and enhance the therapeutic ratio of radiotherapy in patients with pelvic tumors through suppressing the NF-kB/TGF-β1/MMP-9 signaling pathway.

Role and significance of traditional Chinese medicine in regulating gastrointestinal microecology to prevent and treat gastrointestinal cancer

Recent studies have shown that gastrointestinal microecology is closely related to the occurrence and development of gastrointestinal cancers and anti-tumor treatment efficacy, so effective regulation of gastrointestinal microecology plays an important role in the prevention and treatment of gastrointestinal cancers. Traditional Chinese medicine, adopting oral administration, can directly regulate gastrointestinal microecology. Traditional Chinese medicine can improve the precancerous condition and enhance the clinical efficacy of anti-tumor treatment via multiple mechanisms, such as improving the microecological structure of the gastrointestinal tract, protecting the gastrointestinal mucosal barrier, preventing the translocation of the flora, and enhancing the immune function of the gastrointestinal mucosa. Some research has shown that the imbalance of gastrointestinal microecology is closely related to spleen deficiency syndrome and damp-heat syndrome. The therapeutic principles of traditional Chinese medicine can be Jianpi Hewei and Qingre Qushi following the concept of "combination of disease and syndrome". It is of great significance to prevent and cure gastrointestinal tumors from a new perspective of regulating intestinal microecology. We hope of providing new strategies for the anti-tumor research of traditional Chinese medicine.

Food Supplements to Mitigate Detrimental Effects of Pelvic Radiotherapy

Pelvic radiotherapy has been frequently reported to cause acute and late onset gastrointestinal (GI) toxicities associated with significant morbidity and mortality. Although the underlying mechanisms of pelvic radiation-induced GI toxicity are poorly understood, they are known to involve a complex interplay between all cell types comprising the intestinal wall. Furthermore, increasing evidence states that the human gut microbiome plays a role in the development of radiation-induced health damaging effects. Gut microbial dysbiosis leads to diarrhea and fatigue in half of the patients. As a result, reinforcement of the microbiome has become a hot topic in various medical disciplines. To counteract GI radiotoxicities, apart from traditional pharmacological compounds, adjuvant therapies are being developed including food supplements like vitamins, prebiotics, and probiotics. Despite the easy, cheap, safe, and feasible approach to protect patients against acute radiation-induced toxicity, clinical trials have yielded contradictory results. In this review, a detailed overview is given of the various clinical, intestinal manifestations after pelvic irradiation as well as the role of the gut microbiome herein. Furthermore, whilst discussing possible strategies to prevent these symptoms, food supplements are presented as auspicious, prophylactic, and therapeutic options to mitigate acute pelvic radiation-induced GI injury by exploring their molecular mechanisms of action.

Purified PEGylated human glucagon-like peptide-2 reduces the severity of irradiation-induced acute radiation enteritis in rats

Radiation-induced acute intestinal injury after abdominal and pelvic irradiation is a common and serious problem in the clinical setting. Glucagon-like peptide-2 (GLP-2), a 33-amino acid peptide, exerts diverse effects related to the regulation of gastrointestinal growth and function. However, GLP-2 is relatively unstable in vivo. The aim of the present study was to improve GLP-2 stability in vivo and to evaluate its therapeutic effect on acute radiation enteritis. We generated long-lasting intestinal protection peptides by conjugating human GLP-2 (hGLP-2) peptides to polyethyleneglycol (PEG) to produce mPEGylation hGLP-2 (Mono-PEG-hGLP-2) through an enzymatic site-specific transglutamination reaction. Mono-PEG-hGLP-2 synthesized under optimal reaction conditions and separated by one-step ion-exchange chromatography was found to be resistant to degradation in vitro. Pretreatment with Mono-PEG-hGLP-2 reduced the severity of radiation-induced intestinal injury, oxidative stress, and the expression of NF-κB in rats with irradiation-induced acute radiation enteritis. The enhanced biological potency of Mono-PEG-hGLP-2 highlights its potential as a therapeutic agent for intestinal diseases.

The Microbiome and Radiation Induced-Bowel Injury: Evidence for Potential Mechanistic Role in Disease Pathogenesis

Radiotherapy has played a major role in both the curative and palliative treatment of cancer patients for decades. However, its toxic effect to the surrounding normal healthy tissue remains a major drawback. In cases of intra-abdominal and/or pelvic malignancy, healthy bowel is inevitably included in the radiation field, causing undesirable consequences that subsequently manifest as radiation-induced bowel injury, which is associated with significant morbidity and mortality. The pathophysiology of radiation-induced bowel injury is poorly understood, although we now know that it derives from a complex interplay of epithelial injury and alterations in the enteric immune, nervous, and vascular systems in genetically predisposed individuals. Furthermore, evidence supporting a pivotal role for the gut microbiota in the development of radiation-induced bowel injury has been growing. In this review, we aim to appraise our current understanding of radiation-induced bowel injury and the role of the microbiome in its pathogenesis as well as prevention and treatment. Greater understanding of the relationship between the disease mechanism of radiation-induced bowel injury and gut microbiome might shed light on potential future prevention and treatment strategies through the modification of a patient's gut microbiome.

Rebamipide alleviates radiation-induced colitis through improvement of goblet cell differentiation in mice

BACKGROUND AND AIM

Radiation-induced colitis is a common clinical problem associated with radiotherapy and accidental exposure to ionizing radiation. Goblet cells play a pivotal role in the intestinal barrier against pathogenic bacteria. Rebamipide, an anti-gastric ulcer drug, has the effects to promote goblet cell proliferation. The aim of this study was to investigate whether radiation-induced colonic injury could be alleviated by rebamipide.

METHODS

This study orally administered rebamipide for 6 days to mice, which were subjected to 13 Gy abdominal irradiation, to evaluate the therapeutic effects of rebamipide against radiation-induced colitis. To confirm the effects of rebamipide on irradiated colonic epithelial cells, this study used the HT29 cell line.

RESULTS

Rebamipide clearly alleviated the acute radiation-induced colitis, as reflected by the histopathological data, and significantly increased the number of goblet cells. The drug also inhibited intestinal inflammation and protected from bacterial translocation during acute radiation-induced colitis. Furthermore, rebamipide significantly increased mucin 2 expression in both the irradiated mouse colon and human colonic epithelial cells. Additionally, rebamipide accelerated not only the recovery of defective tight junctions but also the differentiation of impaired goblet cells in an irradiated colonic epithelium, which indicates that rebamipide has beneficial effects on the colon.

CONCLUSIONS

Rebamipide is a therapeutic candidate for radiation-induced colitis, owing to its ability to inhibit inflammation and protect the colonic epithelial barrier.

The Potential Role of Probiotics in Cancer Prevention and Treatment

The human gut microbiota has a significant effect on many aspects of human physiology such as metabolism, nutrient absorption, and immune function. Imbalance of the microbiota has been implicated in many disorders including inflammatory bowel disease, obesity, asthma, psychiatric illnesses, and cancers. As a kind of functional foods, probiotics have been shown to play a protective role against cancer development in animal models. Clinical application of probiotics indicated that some probiotic strains could diminish the incidence of postoperative inflammation in cancer patients. Chemotherapy or radiotherapy-related diarrhea was relieved in patients who were administered oral probiotics. The present review summarizes the up-to-date studies on probiotic effects and the underlying mechanisms related to cancer. At present, it is commonly accepted that most commercial probiotic products are generally safe and can improve the health of the host. By modulating intestinal microbiota and immune response, some strains of probiotics can be used as an adjuvant for cancer prevention or/and treatment.

The effect of probiotics for preventing radiation-induced morphological changes in intestinal mucosa of rats

Radiation therapy is an important treatment modality for abdominal or pelvic cancer, but there is a common and serious complication such as radiation-induced enteritis. Probiotics is reported to have positive effects against radiation-induced enteropathy. In this study, morphological changes of bowel mucosa were analyzed in rats to presume the effect of probiotics on radiation-induced enteritis and its correlation with radiation dose. A total of 48 adult male Sprague-Dawley rats were randomly assigned to two groups and received a solution containing 1.0×10(8) colony-forming units of Lactiobacillus acidophilus or water once daily for 10 days. Each of two groups was divided into three subgroups and abdomino-pelvic area of each subgroup was irradiated with 10, 15, and 20 Gy, respectively on the seventh day of feeding the solutions. All rats were sacrificed 3 days after irradiation and the mucosal thickness and villus height of jejunum, ileum and colon were measured. The morphological parameters of the small intestine represented significant differences between two solution groups irradiated 10 or 15 Gy, except for villus height of jejunum in 15 Gy-subgroup (P=0.065). There was no significant morphometric difference between two groups irradiated with 20 Gy of radiation. Probiotics appear to be effective for the morphological shortening of small intestinal mucosa damaged by radiation less than or equal to 15 Gy.

Microbiota and radiation-induced bowel toxicity: lessons from inflammatory bowel disease for the radiation oncologist

New gastrointestinal symptoms are frequent after pelvic radiotherapy and can greatly affect the quality of life of cancer survivors. The effect of radiation on the intestinal microbiota, and the clinical implications of a modified microbial balance after radiotherapy are now beginning to emerge. In this Personal View, we show the importance of the microbiota for intestinal homoeostasis, and discuss the similarity between inflammatory bowel disease, which has been extensively researched, and radiation-induced gastrointestinal toxicity. By use of microbiota profiles for risk assessment and manipulation of the intestinal flora for prevention and treatment of radiation, enteropathy could become a reality and would be of substantial relevance to the increasing numbers of long-term cancer survivors.

Radiation enteritis

Radiation enteritis continues to be a major health concern in recipients of radiation therapy. The incidence of radiation enteritis is expected to continue to rise during the coming years paralleling the unprecedented use of radiotherapy in pelvic cancers. Radiation enteritis can present as either an acute or chronic syndrome. The acute form presents within hours to days of radiation exposure and typically resolves within few weeks. The chronic form may present as early as 2 months or as long as 30 years after exposure. Risk factors can be divided into patient and treatment-related factors. Chronic radiation enteritis is characterized by progressive obliterative endarteritis with exaggerated submucosal fibrosis and can manifest by stricturing, formation of fistulae, local abscesses, perforation, and bleeding. In the right clinical context, diagnosis can be confirmed by cross-sectional imaging, flexible or video capsule endoscopy. Present treatment strategies are directed primarily towards symptom relief and management of emerging complications. Recently, however, there has been a shift towards rational drug design based on improved understanding of the molecular basis of disease in an effort to limit the fibrotic process and prevent organ damage.

The effect of synbiotics on acute radiation-induced diarrhea and its association with mucosal inflammatory and adaptive responses in rats

BACKGROUND

Previous clinical studies advocated that probiotics beneficially affect acute radiation-induced diarrhea. These encouraging results were attributed to the restoration of the intestinal flora; however, there is lack of evidence if and how probiotics influence the underlying pathophysiological mechanisms.

AIMS

The present study was conducted to investigate the potential supporting role of a synbiotic preparation (combination of pro- and pre-biotics) on experimentally-induced acute radiation diarrhea from the perspective of mucosal inflammation and histological injury.

METHODS

Ninety adult Wistar rats were randomly assigned into six groups. Group A (non-irradiated), group B (non-irradiated/synbiotic supplemented), group C (irradiated), and group D (irradiated/synbiotic supplemented) were followed up to a week after the beginning of the experiment. Group E (irradiated) and group F (irradiated/synbiotic supplemented) were followed up for four days. On the last day of the experiments tissues were harvested for structural and molecular assessments.

RESULTS

Synbiotic administration could not avert the occurrence of diarrhea, but significantly attenuated its severity. This effect was associated with the significant downregulation of neutrophil accumulation and lipid peroxidation during the acute phase. During the subacute phase, synbiotic treatment significantly improved both the histological profile and radiation mucositis. These mechanisms significantly contributed to the rehabilitation of the intestinal absorptive function as further indicated from the significantly reduced weight loss.

CONCLUSIONS

Given the optimization of the intestinal flora exerted by synbiotics, the resolution of diarrhea relies on the suppression of the "reactive" and the augmentation of "regenerative" components of acute radiation-induced intestinal response.

Probiotic bacteria in cancer patients undergoing chemotherapy and radiation therapy

BACKGROUND

Probiotics are live microorganisms, which as drugs or food supplements help to maintain health beneficial microbial balance in the digestive tract of a human or other host. Probiotics by their properties may help strengthen homeostasis and thus reduce side effects associated with cancer treatment. Experimental evidence suggests that probiotics might have beneficial effect on the toxicity of anticancer therapy.

METHODS

A computer-based literature search was carried out using PubMed (keywords: "probiotic" and "lactic acid bacteria" in association with the search terms "cancer" or "oncology" or "chemotherapy" or "radiation"); data reported at international meetings were included.

RESULTS

Probiotics might have beneficial effects on some aspects of toxicity related to anticancer treatment especially radiation therapy. However, reported trials vary in utilized probiotic strains, dose of probiotics and vast majority of them are small trials with substantial risk of bias. Despite limited data, it seems that probiotic bacteria as live microorganisms could be safely administered even in the setting of neutropenia.

CONCLUSIONS

Current evidence supporting probiotic use as adjunctive therapy to anticancer treatment is limited, especially in cancer patients treated with chemotherapy. Well designed clinical trials are needed to find true role of probiotics in oncology.

Changes in biologic markers of oxidative stress and plasma endotoxin levels in gynecologic cancer patients treated with pelvic radiotherapy: a pilot study

Objective

We conducted a pilot study to evaluate the effects of pelvic radiotherapy on biologic markers of oxidative stress and plasma endotoxin levels, and to assess the relationship between the changes of such factors and radiotherapy-related complications.

Methods

Twelve gynecologic cancer patients who were treated via pelvic radiotherapy with or without concurrent chemotherapy were enrolled in this study. Biologic markers of oxidative stress, such as glutathione (GSH) and oxidized glutathione (GSSG), as well as endotoxin levels, were measured weekly during treatment. Subjective symptoms were assessed using the Korean version of the EORTC QLQ-C30 at the baseline and on the 5th week of radiotherapy.

Results

No changes were noted in the level of GSH in whole blood, but the GSH/GSSG ratio was reduced dramatically after the initiation of radiotherapy. The mean plasma endotoxin for all patients tended to increase and persisted during radiotherapy, and the number of patients who evidenced clinically significant endotoxin levels (defined as >0.005 EU/mL) also increased. Nausea/vomiting and diarrhea were significantly changed (p=0.019 and p<0.001, respectively). A significant relationship was noted to exist between the changes in the endotoxin level and nausea/vomiting (p=0.001). However, such symptoms did not correlate with the changes of oxidative stress markers.

Conclusion

Pelvic radiotherapy oxidized the GSH redox system and increased plasma endotoxin. Further investigations containing interventional and longitudinal studies will be required to assess the effects of the changes in oxidative stress markers and endotoxin on radiotherapy-related adverse events.

Antioxidant properties of probiotics and their protective effects in the pathogenesis of radiation-induced enteritis and colitis

Radiation therapy has become one of the most important treatment modalities for human malignancy, but certain immediate and delayed side-effects on the normal surrounding tissues limit the amount of effective radiation that can be administered. After exposure of the abdominal region to ionizing radiation, nearly all patients experience transient symptoms of irradiation of the bowel. Acute-phase symptoms may persist for a short time, yet long-term complications can represent significant clinical conditions with high morbidity. Data from both experimental studies and clinical trials suggest the potential benefit for probiotics in radiation-induced enteritis and colitis. On the other hand, it is well evidenced that both useful and harmful effects of therapeutic applications of ionizing radiation upon living systems are ascribed to free-radical production. Therefore, the hypothesis that probiotics reinforce antioxidant defense systems of normal mucosal cells exposed to ionizing radiation may explain to an extent their beneficial action. The aim of this review is threefold: First, to make a short brief into the natural history of radiation injury to the intestinal tract. Second, to describe the primary interaction of ionizing radiation at the cellular level and demonstrate the participation of free radicals in the mechanisms of injury and, third, to try a more profound investigation into the antioxidant abilities of probiotics and prebiotics based on the available experimental and clinical data.

Microbial influences on the small intestinal response to radiation injury

PURPOSE OF REVIEW

Injury to the small bowel from ionizing radiation occurs commonly in patients undergoing cancer therapy and less commonly in instances of accidental radiation overexposure. Several lines of evidence now suggest that dynamic interactions between the host's enteric microbiota and innate immune system are important in modulating the intestinal response to radiation. Here, we will review recent developments in the area of acute radiation enteropathy and examine the current state of knowledge regarding the impact of host-microbial interactions in the process.

RECENT FINDINGS

There is promise in the development and testing of new clinical biomarkers including serum citrulline. Toll-like receptor agonists and innate immune system signaling pathways including nuclear factor-kappa B profoundly alter intestinal epithelial cell apoptosis and crypt survival after radiation exposure. Germ-free conditions, probiotics and antibiotics are each identified as modifiers of disease development and course. A human study suggested that luminal microbiota composition may influence the host's intestinal response to radiation and may change in those developing postradiation diarrhea.

SUMMARY

New knowledge implies that investigations aimed at deciphering the microbiome-host interactions before and after small bowl radiation injury may eventually allow prediction of disease course and offer opportunities for the development of novel therapeutic or prophylactic strategies.

Preventive effect of pentoxifylline on acute radiation damage via antioxidant and anti-inflammatory pathways

PURPOSE

The aim of the present study was to investigate whether pentoxifylline (PTX) treatment could protect against induced acute radiation enteritis.

METHOD

Rats received 100 mg/kg/day PTX for 7 days before irradiation and continued on treatment for 3 days after irradiation. The intestinal myeloperoxidase (MPO) activities and malondialdehyde (MDA), glutathione (GSH), prostaglandin E2, and thromboxane B2 levels were determined. Terminal ileum tissue was evaluated for morphological changes. Also, nuclear factor kappa (NF-kappa), tumor necrosis factor-alpha (TNF-alpha), and intercellular adhesion molecule 1 (ICAM-1) expressions were analyzed with immunohistochemisty methods.

RESULTS

PTX treatment was associated with increased GSH levels and decreased MPO activity and MDA, prostaglandin E2, and thromboxane B2 levels. Histopathologic examination showed that intestinal mucosal structure was preserved in the PTX-treated group while having significant decreases in NF-kappaB, TNF-a, and ICAM-1 expression.

CONCLUSIONS

PTX appears to have a protective effect against radiation damage. This protective effect is mediated in part by decreasing both inflammatory reactions and oxidative stress.

Endotoxin-binding affinity of sevelamer: a potential novel anti-inflammatory mechanism

Chronic inflammation is highly prevalent in patients with chronic kidney disease (CKD), and is associated with increased cardiovascular morbidity and mortality. There are numerous causes of inflammation in CKD, including the potential exposure to bacterial lipopolysaccharide (LPS) in the bloodstream from the intestinal tract as a result of uremia-related increases in intestinal permeability. Sevelamer, a commonly prescribed non-calcium, non-metal-based phosphate binder in CKD, also possesses putative anti-inflammatory properties, as its use has been associated with a reduction in systemic markers of inflammation. Emerging studies have provided direct evidence that sevelamer shows in vitro LPS-binding properties. Indirect clinical evidence suggests that sevelamer might also limit translocation of LPS from the intestinal lumen into the bloodstream. This review focuses on bacterial LPS as a source of chronic inflammation in CKD, and proposes that sevelamer might possess novel anti-inflammatory properties as a result of LPS binding in the intestinal tract. The proposed hypothesis that intestinal LPS-binding by sevelamer may lower circulating LPS, and in turn systemic inflammation, requires further evaluation in a clinical trial.

Probiotic therapy in radiation-induced intestinal injury and repair

Intestinal injury from ionizing radiation is a clinically important entity, as enteritis symptoms occur commonly after radiotherapy for pelvic malignancies. Preventative or therapeutic options for radiation enteritis are mostly unsatisfactory; however, available data suggests that probiotic bacteria--those which confer health benefit--may have therapeutic value. Previous reports from both human trials and animal models have evaluated various end points for probiotic usage in limiting radiation-associated intestinal damage. Newer data suggests that particular probiotics and/or their secreted or derived bacterial products may have unique radioprotective properties. We will review the area with a focus on new developments surrounding probiotic therapy in radiation-induced intestinal injury and repair.

Effects of probiotics for the prevention and treatment of radiation-induced diarrhea

BACKGROUND AND AIMS

Probiotic supplementation seems to provide beneficial effects in the prevention and treatment of radiation-induced diarrhea. We performed a systematic review and meta-analysis to estimate the efficacy of probiotic supplementation for prevention and treatment of radiation-induced diarrhea.

METHODS

Two reviewers independently searched PubMed, EMBASE, Cochrane Library, Google Scholar and on-line clinical trials registers (up to January 2009) for randomized controlled trials that evaluated the efficacy of probiotic supplementation for the prevention and treatment of radiation-induced diarrhea. Each clinical trial was separately evaluated for study characteristics, methodologic quality and outcomes. Results of the randomized controlled trials were pooled in a meta-analysis.

RESULTS

Four randomized controlled trials were included. Three clinical trials, with a total of 632 subjects, evaluated the preventive effects of probiotic supplementation and 1 study evaluated the therapeutic role. Random effects meta-analysis of the preventive trials did not show significant differences between probiotic supplementation and control groups (odds ratio 0.47; 95% confidence interval: 0.13-1.67). However, the few available trials and the presence of significant clinical and statistical heterogeneity limited the analysis. Similarly, the therapeutic clinical trial did not show significant differences between active and placebo groups. No major adverse events owing to probiotic supplementation were reported in any study.

CONCLUSIONS

Probiotic supplementation showed beneficial effect in the prevention and treatment of radiation-induced diarrhea in experimental animal studies. Encouraging results have been observed in humans; however, the few available clinical studies do not allow firm conclusions. More well-performed, randomized placebo-controlled studies are needed.