title: Clinical risk factors for late intestinal toxicity after radiotherapy: a systematic review protocol.
abstract: BACKGROUND
  Late intestinal toxicity after radiotherapy (LITAR) not only limits the radiation dose, which subsequently leads to unfavorable clinical outcomes, but also significantly lowers the quality of life in an increasing number of cancer survivors. Therefore, identifying clinical risk factors for LITAR is important for establishing a predictive model in the clinical setting of decision-making for these patients. This review aims to systematically summarize and clarify the clinical factors that can be potentially associated with an increased risk of moderate/severe LITAR in patients with abdominal or pelvic malignancies.
  
  
  METHODS
  MEDLINE, EMBASE, Web of Science, Cochrane Central Register of Controlled Trials, Scopus, Google Scholar and Chinese BioMed will be systematically searched to identify appropriate studies. Citations of the retrieved studies and recent reviews will also be searched separately by case.The enrolled studies should at least have the following information: (1) a clear definition and information on the LITAR severity; (2) assess clinical factors for moderate/severe toxicity with adjusted risk estimates; (3) have a cohort, case-control, randomized controlled trial and controlled clinical trial study design.Two authors will independently review the abstract and full text of retrieved studies, extract data from eligible studies and assess the risk of bias. Disagreements will be discussed among reviewers until a consensus is reached. The effect of identified risk factors will be displayed in forest plots. If the information is sufficient, results will be synthesized by a meta-analysis with the random effects model to pool the estimate of risk posed by clinical factors. Subgroup and sensitivity analysis will be used to explore the sources of heterogeneity.
  
  
  CONCLUSIONS
  This review will summarize the evidence of clinical risk factors for moderate/severe LITAR. The results may help guide decision-making and minimize the side effects of therapeutic modalities in the clinical setting.
authors.affiliation: Department of Colorectal Surgery, Sixth Affiliated Hospital, Sun Yat-sen University, 26 Yuancun Er Heng Road, Guangzhou, 510655 Guangdong, PR China.
authors.forename: Qiyuan
authors.initials: Q
authors.lastname: Qin
authors.forename: Qingshan
authors.initials: Q
authors.lastname: Huang
authors.forename: Qinghua
authors.initials: Q
authors.lastname: Zhong
authors.forename: Xinjuan
authors.initials: X
authors.lastname: Fan
authors.forename: Dianke
authors.initials: D
authors.lastname: Chen
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
mesh_terms: D004751:Enteritis / Q000209:etiology*; D006801:Humans; D007422:Intestines / Q000528:radiation effects*; D015201:Meta-Analysis as Topic; D009369:Neoplasms / Q000150:complications / Q000532:radiotherapy*; D011832:Radiation Injuries / Q000209:etiology*; D011839:Radiation, Ionizing; D012107:Research Design; D012307:Risk Factors; D000078202:Systematic Reviews as Topic