Abstract
Pelvic radiotherapy is the key treatment for pelvic malignancies, usually including pelvic primary tumour lesions and lymphatic drainage areas in the pelvic region. Therefore, the intestinal tract in the radiation field is inevitably damaged, a phenomenon clinically referred to as radiation enteritis, and diarrhoea is the most common clinical symptom of radiation enteritis. Therefore, it is necessary to study the mechanism of radiation-induced diarrhoea. It has been found that the gut microbiome plays an important role in the development of diarrhoea in response to pelvic radiotherapy, and the species and distribution of intestinal microbiota are significantly altered in patients after pelvic radiotherapy. In this study, we searched for articles indexed in the Cochrane Library, Web of Science, EMBASE and PubMed databases in English and CNKI, Wanfang data and SINOMED in Chinese from their inception dates through 13 March 2020 to collect studies on the gut microbiome in pelvic radiotherapy patients. Eventually, we included eight studies: one study report on prostatic carcinoma, five studies on gynaecological carcinoma and two papers on pelvic carcinomas. All studies were designed as self-controlled studies, except for one that compared toxicity to nontoxicity. The results from all the studies showed that the diversity of intestinal flora decreased during and after pelvic radiotherapy, and the diversity of intestinal flora decreased significantly in patients with diarrhoea after radiotherapy. Five studies observed that the community composition of the gut microbiota changed at the phylum, order or genus level before, during, and after pelvic radiotherapy at different time points. In addition, the composition of the gut microbiota before radiotherapy was different between patients with postradiotherapy diarrhoea and those without diarrhoea in five studies. However, relevant studies have not reached consistent results regarding the changes in microbiota composition. Changes in the intestinal flora induced by pelvic radiotherapy and their relationship between changes in intestinal flora and the occurrence of radiation-induced diarrhoea (RID) are discussed in this study, providing a theoretical basis for the causes of RID after pelvic radiotherapy.
Highlights
IntroductionIn patients undergoing pelvic radiotherapy, damage to normal organs and tissues in the pelvic region is inevitable during treatment
More than 50% of cancer patients receive radiotherapy for cancer treatment [1, 2]
Forty-nine articles were subsequently excluded after reviewing the full text, three of which were articles on changes in the intestinal microbiota caused by nonpelvic radiotherapy
Summary
In patients undergoing pelvic radiotherapy, damage to normal organs and tissues in the pelvic region is inevitable during treatment. Among these normal organs, the intestinal bowel is one of the most radiationsensitive organs, and radiation injury inevitably occurs in the intestine in the radiation field. In the large EORTC 22,921 trial that investigated preoperative and postoperative therapies for rectal cancer, the incidence of grade 2 or higher diarrhoea was 17% in patients receiving preoperative radiation therapy (45 Gy in 25 fractions) and 34% in patients receiving concurrent infusion of 5-fluorouracil(5FU) [6]. In the RTOG1203 study, acute toxicity and health-related quality of life were compared between patients with cervical and endometrial cancer reported during treatment to standard pelvic radiotherapy or intensity-modulated radiotherapy (IMRT). RID further impairs quality of life and leads to interruption and delays in the radiotherapy process, resulting in suboptimal treatment
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