Types of studies

Only randomised controlled trials (RCTs) of parallel study design , where the allocation of concealment is adequate or not reported will be eligible for inclusion in this review. Quasi‐randomised trials will be decided for their inclusion or exclusion for this review subject to editorial and peer review decision.

Types of participants

RCTs involving adults (18 years and over) presented clinically with large bowel obstruction secondary to colorectal cancer confirmed radiologically will be included irrespective of race, sex and associated medical conditions undergoing either colonic stent placement or surgical interventions.

Types of interventions

Studies reporting the following comparisons will be eligible for inclusion in this review. Studies will be included irrespective of the methods used for colonic stent deployment either through endoscope or through fluoroscopic radiology guided or through endoscope and fluoroscopic guided.

• Colonic stent compared with stoma creation for malignant colonic obstruction as palliative procedure

• Colonic stent compared with stoma creation for malignant colonic obstruction as a bridge to a definitive surgical procedure

• One type of colonic stents compared with another type of colonic stent for malignant colonic obstruction

Types of outcome measures

For the purpose of this review, studies which will report the following outcomes will be eligible for the inclusion.

Electronic searches

We will search the following databases:

• Cochrane Colorectal Cancer Specialised Register (30/04/2008);

• Cochrane Central Register of Controlled Trials (CENTRAL); 2008 issue 3

• Ovid MEDLINE (1950 to May 2008);

• Ovid EMBASE (1970 to May 2008);

• Ovid CINAHL (1970 to May 2008).

We will apply a filter to identify RCTs for all databases except the Colorectal Cancer Group Specialised Register and CENTRAL, using the strategy described in the Cochrane Handbook (Higgins 2008).

The databases used for the literature search will include MEDLINE, EMBASE and Cochrane Controlled Trials Register. These are considered the relevant bibliographic databases in this subject area.

The resulting search results will be uploaded in the reference manager file through reference manager version 11.

Searching other resources

We will consider all the relevant studies irrespective of language and publication status for the review. The reference lists in the identified studies will also be searched in order to identify further studies. We will search to identify any ongoing or completed trials.

Selection of studies

The authors will independently assess the titles and abstracts of the identified studies. We will obtain full articles for all studies that potentially meet the inclusion criteria and will include all those that meet the inclusion criteria. Any differences in opinion between authors at this stage will be resolved by discussion.

Data extraction and management

The authors will independently extract data for the outcomes listed and will independently assess the methodological quality of each trial, without masking of author names. In addition, we will extract the following data for each study using a custom designed extraction form:

• Language of publication

• Country where study conducted

• Baseline characteristics of participants by group

• Type of interventions ‐ colonic stent/surgery

• Type of stents

• Details of the comparison intervention

• Co‐interventions (by group)

• Duration of follow up

• Inclusion and exclusion criteria.

We will contact the study authors regarding any unclear or missing information. We will identify any studies that potentially share the same patients, and in such cases, we will contact the authors of the studies to clarify this issue.

Assessment of risk of bias in included studies

Assessment of risk of bias in the trial will be based on guidelines in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2008). If information won't be available in the published study, we will contact the authors in order to assess the trials correctly.

The elements of risk of bias assessment will be generation of allocation sequence, allocation concealment, blinding, incomplete data outcomes, selective data reporting, and other bias (early stopping, baseline imbalance, source of funding):

(1) Generation of the allocation sequence

• Adequate (A), if the allocation sequence is generated by a computer or random number table. Drawing of lots, tossing of a coin, shuffling of cards, or throwing dice will be considered as adequate if a person who is not otherwise involved in the recruitment of participants performed the procedure.

• Unclear (B), if the trial is described as randomised, but the method used for the allocation sequence generation is not described.

• Inadequate (C), if a system involving dates, names, or admittance numbers is used for the allocation of patients. These studies are known as quasi‐randomised and will be excluded from the review.

(2) Allocation concealment

• Adequate (A), if the allocation of patients involves a central independent unit, on‐site locked computer, or sealed envelopes.

• Unclear (B), if the trial is described as randomised, but the method used to conceal the allocation is not described.

• Inadequate (C), if the allocation sequence is known to the investigators who assign participants or if the study is quasi‐randomised.

(3) Blinding of participant

• Adequate (A), if the participant is described as blinded and the method of blinding is described.

• Unclear (B), if the participant is described as blinded, but the method of blinding is not described.

• Not performed (C), if there is no blinding at all.

(4) Blinding of care‐provider

• Adequate (A), if the care provider is described as blinded and the method of blinding is described.

• Unclear (B), if the care provider is described as blinded, but the method of blinding is not described.

• Not performed (C), if there is no blinding at all.

(5) Blinding of outcome assessor

• Adequate (A), if the outcome assessor was described as blinded and the method of blinding was described.

• Unclear (B), if the outcome assessor was described as blinded, but the method of blinding was not described.

• Not performed (C), if there was no blinding at all.

(6) Incomplete data outcomes

• Adequate (A), if there are no post‐randomisation drop‐outs or withdrawals or if the post‐randomisation drop‐outs are balanced in both groups or reasons for missing data unlikely to be related to true outcome (for example, patient does not need either surgery or stent due to resolution of bowel obstruction).

• Unclear (B), if it is not clear whether there are any drop‐outs or withdrawals or if the reasons for these drop‐outs are not clear.

• Inadequate (C), if the reasons for missing data likely to be related to true outcomes, "as‐treated" analysis is performed, potentially inappropriate application of simple imputation, potential for patients with missing outcomes to induce clinically relevant bias in effect estimate or effect size.

(7) Selective outcome reporting

• Adequate (A), if all the important outcomes are reported or if the study protocol is available and all of the study’s pre‐specified (primary and secondary) outcomes that are of interest in the review are reported in the pre‐specified way.

• Unclear (B), if there is insufficient information to assess whether the risk of selective outcome reporting is present.

• Inadequate (C), if not all the pre‐specified outcomes are reported or if the primary outcomes are changed or if some of the important outcomes are incompletely reported.

(8) Other biases

(a) Early stopping

• Adequate (A), if sample size calculations are reported and the trial is not stopped early by formal or informal stopping rules.

• Unclear (B), if sample size calculations are not reported and it is not clear whether the trial is not stopped early.

• Inadequate (C), if the trial is stopped early.

Measures of treatment effect

We will use the software package RevMan 5.0 provided by The Cochrane Collaboration. For dichotomous variables, we will calculate the risk ratio (RR) with 95% confidence interval. For continuous outcomes we plan to enter the mean and standard deviation data into RevMan and calculate the weighted mean difference.

Unit of analysis issues

The unit of allocation is individual participants. We will not consider cluster‐randomised trials for inclusion.

Dealing with missing data

We plan to use an "available case analysis" i.e. whether participants are analysed in the groups to which they are originally randomised (Hollis 1999; Higgins 2008) without imputing any data for the patients for whom the outcomes are not reported. In case, the authors have not report the standard deviation for continuous outcomes (and if we are unable to obtain this information from authors), we plan to impute the standard deviation from standard error, confidence intervals, or p‐values using formulae given in the Cochrane handbook (Higgins 2008). If it is not possible to impute the standard deviation from these measures, we plan to use the maximum standard deviation for the same measure in other trials (Higgins 2008). When medians are reported without the means, we will not include the median as a substitute for mean in the meta‐analysis (see also "Sensitivity analysis") . However, if there are no post‐randomisation drop‐outs or withdrawals from the trials included in this review, we may have to consider this as "intention‐to‐treat analysis".

Assessment of heterogeneity

We will explore heterogeneity using I² and p‐value from the chi‐squared test.

Assessment of reporting biases

Data synthesis

We will perform the meta‐analyses according to the recommendations of The Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2008). We will use the Mantel‐Haenzel's methods to perform the meta‐analysis. We will use a random‐effects model (DerSimonian 1986) and a fixed‐effect model (Demets 1987). In case of discrepancy between the two models we will report both results; otherwise we will report only the results from the fixed‐effect model

Subgroup analysis and investigation of heterogeneity

It we find more than one trial, we will perform subgroup analyses to explore the effects of aspects of trials with adequate, unclear or inadequate risks of bias. We will also perform a subgroup analysis of different varieties of stents. For the subgroup analysis, we intend to use the inverse‐variance method of meta‐analysis and use the chi‐squared test for identifying subgroup differences (Higgins 2008). We also plan to use meta‐regression to investigate heterogeneity using factors such as type of stents and prophylactic antibiotic use (antibiotic used, route, duration) if there are enough trials.

Sensitivity analysis

We intend to perform a sensitivity analysis using medians directly in the meta‐analysis and determine if this changes the results of the meta‐analysis. In case if we find 'zero‐event' trials (i.e., zero event in both groups) in statistically significant outcomes, we plan to perform a sensitivity analysis by adding up to 4 in each arm to numerator and denominator (to obtain a risk rate of 4 per 100) (Higgins 2008).