Dietary fibre for the prevention of recurrent colorectal adenomas and carcinomas

Yibo Yao; Tao Suo; Roland Andersson; Yongqing Cao; Chen Wang; Jingen Lu; Evelyne Chui

doi:10.1002/14651858.CD003430.pub2

Fibra dietética para prevenir a recorrência de adenomas e carcinomas colorretais

Appendices

Appendix 1. Cochrane Library search strategy

#1 MeSH descriptor: [Cereals] explode all trees

#2 MeSH descriptor: [Dietary Fiber] explode all trees

#3 MeSH descriptor: [Dietary Carbohydrates] explode all trees

#4 (wholemeal$ or whole meal$ wholegrain$ or whole grain$ or cereal$ or grain$ or starch or high‐fiber or fibre or fiber or dietary intervention or dietary carbohydrate$ or roughage$ or wheat bran$)

#5 (#1 or #2 or #3 or #4)

#6 MeSH descriptor: [Colorectal Neoplasms] explode all trees

#7 MeSH descriptor: [Colonic Polyps] explode all trees

#8 ((colorect$ or colon$ or rect$ or anal$ or anus$ or intestin$ or bowel$) near/3 (carcinom$ or neoplas$ or adenocarcinom$ or cancer$ or tumor$ or tumour$ or sarcom$ or polyp$ or adenom$))

#9 (#6 or #7 or #8)

#10 (#5 and #9)

Appendix 2. MEDLINE search strategy

1. exp Cereals/

2. exp Dietary Fiber/

3. exp Dietary Carbohydrates/

4. (wholemeal$ or whole meal$ wholegrain$ or whole grain$ or cereal$ or grain$ or starch or high‐fiber or fibre or fiber or dietary intervention or dietary carbohydrate$ or roughage$ or wheat bran$).mp.

5. 1 or 2 or 3 or 4

6. exp Colorectal Neoplasms/

7. exp Colonic Polyps/

8. ((colorect$ or colon$ or rect$ or anal$ or anus$ or intestin$ or bowel$) adj3 (carcinom$ or neoplas$ or adenocarcinom$ or cancer$ or tumor$ or tumour$ or sarcom$ or polyp$ or adenom$)).mp.

9. 6 or 7 or 8

10. 5 and 9

11. randomized controlled trial.pt.

12. controlled clinical trial.pt.

13. randomized.ab.

14. placebo.ab.

15. clinical trial as topic.sh.

16. randomly.ab.

17. trial.ti.

18. 11 or 12 or 13 or 14 or 15 or 16 or 17

19. exp animals/ not humans.sh.

20. 18 not 19

21. 10 and 20

Appendix 3. Embase search strategy

1. *cereal/

2. *dietary fiber/

3. *carbohydrate diet/

4. (wholemeal$ or whole meal$ wholegrain$ or whole grain$ or cereal$ or grain$ or starch or high‐fiber or fibre or fiber or dietary intervention or dietary carbohydrate$ or roughage$ or wheat bran$).m_titl.

5. 1 or 2 or 3 or 4

6. exp large intestine tumor/

7. ((colorect$ or colon$ or rect$ or anal$ or anus$ or intestin$ or bowel$) and (carcinom$ or neoplas$ or adenocarcinom$ or cancer$ or tumor$ or tumour$ or sarcom$ or polyp$ or adenom$)).m_titl.

8. 6 or 7

9. 5 and 8

10. CROSSOVER PROCEDURE.sh.

11. DOUBLE‐BLIND PROCEDURE.sh.

12. SINGLE‐BLIND PROCEDURE.sh.

13. (crossover* or cross over*).ti,ab.

14. placebo*.ti,ab.

15. (doubl* adj blind*).ti,ab.

16. allocat*.ti,ab.

17. trial.ti.

18. RANDOMIZED CONTROLLED TRIAL.sh.

19. random*.ti,ab.

20. 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18 or 19

21. (exp animal/ or exp invertebrate/ or animal.hw. or nonhuman/) not (exp human/ or human cell/ or (human or humans or man or men or wom?n).ti.)

22. 20 not 21

23. 9 and 22

Appendix 4. Criteria for judging risk of bias in the 'Risk of bias' assessment tool

Random sequence generation Selection bias (biased allocation to interventions) due to inadequate generation of a randomised sequence.
Criteria for a judgement of ‘low risk’ of bias	The investigators describe a random component in the sequence generation process such as: referring to a random number table; using a computer random number generator; coin tossing; shuffling cards or envelopes; throwing dice; drawing of lots; minimisation. Minimisation may be implemented without a random element, and this is considered to be equivalent to being random.
Criteria for the judgement of ‘high risk’ of bias	The investigators describe a non‐random component in the sequence generation process. Usually, the description would involve some systematic, non‐random approach, for example: sequence generated by odd or even date of birth; sequence generated by some rule based on date (or day) of admission; sequence generated by some rule based on hospital or clinic record number. Other non‐random approaches happen much less frequently than the systematic approaches mentioned above and tend to be obvious. They usually involve judgement or some method of non‐random categorisation of participants, for example: allocation by judgement of the clinician; allocation by preference of the participant; allocation based on the results of a laboratory test or a series of tests; allocation by availability of the intervention.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information about the sequence generation process to permit judgement of ‘low risk’ or ‘high risk’
Allocation concealment Selection bias (biased allocation to interventions) due to inadequate concealment of allocations prior to assignment.
Criteria for a judgement of ‘low risk’ of bias	Participants and investigators enrolling participants could not foresee assignment because one of the following, or an equivalent method, was used to conceal allocation: central allocation (including telephone, web‐based and pharmacy‐controlled randomisation); sequentially numbered drug containers of identical appearance; sequentially numbered, opaque, sealed envelopes.
Criteria for the judgement of ‘high risk’ of bias	Participants or investigators enrolling participants could possibly foresee assignments and thus introduce selection bias, such as allocation based on: using an open random allocation schedule (e.g. a list of random numbers); assignment envelopes were used without appropriate safeguards (e.g. if envelopes were unsealed or nonopaque or not sequentially numbered); alternation or rotation; date of birth; case record number; any other explicitly unconcealed procedure.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information to permit judgement of ‘low risk’ or ‘high risk’. This is usually the case if the method of concealment is not described or not described in sufficient detail to allow a definite judgement – for example if the use of assignment envelopes is described, but it remains unclear whether envelopes were sequentially numbered, opaque and sealed.
Blinding of participants and personnel Performance bias due to knowledge of the allocated interventions by participants and personnel during the study.
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: no blinding or incomplete blinding, but the review authors judge that the outcome is not likely to be influenced by lack of blinding; blinding of participants and key study personnel ensured, and unlikely that the blinding could have been broken.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: no blinding or incomplete blinding, and the outcome is likely to be influenced by lack of blinding; blinding of key study participants and personnel attempted, but likely that the blinding could have been broken, and the outcome is likely to be influenced by lack of blinding.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: insufficient information to permit judgement of ‘low risk’ or ‘high risk’; the study did not address this outcome.
Blinding of outcome assessment Detection bias due to knowledge of the allocated interventions by outcome assessors.
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: no blinding of outcome assessment, but the review authors judge that the outcome measurement is not likely to be influenced by lack of blinding; blinding of outcome assessment ensured, and unlikely that the blinding could have been broken.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: no blinding of outcome assessment, and the outcome measurement is likely to be influenced by lack of blinding; blinding of outcome assessment, but likely that the blinding could have been broken, and the outcome measurement is likely to be influenced by lack of blinding.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: insufficient information to permit judgement of ‘low risk’ or ‘high risk’; the study did not address this outcome.
Incomplete outcome data Attrition bias due to amount, nature or handling of incomplete outcome data.
Criteria for a judgement of ‘low risk’ of bias	Any one of the following: no missing outcome data; reasons for missing outcome data unlikely to be related to true outcome (for survival data, censoring unlikely to be introducing bias); missing outcome data balanced in numbers across intervention groups, with similar reasons for missing data across groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk not enough to have a clinically relevant impact on the intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes not enough to have a clinically relevant impact on observed effect size; missing data have been imputed using appropriate methods.
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: reason for missing outcome data likely to be related to true outcome, with either imbalance in numbers or reasons for missing data across intervention groups; for dichotomous outcome data, the proportion of missing outcomes compared with observed event risk enough to induce clinically relevant bias in intervention effect estimate; for continuous outcome data, plausible effect size (difference in means or standardised difference in means) among missing outcomes enough to induce clinically relevant bias in observed effect size; ‘as‐treated’ analysis done with substantial departure of the intervention received from that assigned at randomisation; Potentially inappropriate application of simple imputation.
Criteria for the judgement of ‘unclear risk’ of bias	Any one of the following: insufficient reporting of attrition/exclusions to permit judgement of ‘Low risk’ or ‘High risk’ (e.g. number randomized not stated, no reasons for missing data provided); the study did not address this outcome.
Selective reporting Reporting bias due to selective outcome reporting.
Criteria for a judgement of ‘low risk’ of bias	Any of the following: the study protocol is available and all of the study’s pre‐specified (primary and secondary) outcomes that are of interest in the review have been reported in the pre‐specified way; the study protocol is not available but it is clear that the published reports include all expected outcomes, including those that were pre‐specified (convincing text of this nature may be uncommon).
Criteria for the judgement of ‘high risk’ of bias	Any one of the following: not all of the study’s pre‐specified primary outcomes have been reported; one or more primary outcomes is reported using measurements, analysis methods or subsets of the data (e.g. subscales) that were not pre‐specified; one or more reported primary outcomes were not pre‐specified (unless clear justification for their reporting is provided, such as an unexpected adverse effect); one or more outcomes of interest in the review are reported incompletely so that they cannot be entered in a meta‐analysis; the study report fails to include results for a key outcome that would be expected to have been reported for such a study.
Criteria for the judgement of ‘unclear risk’ of bias	Insufficient information to permit judgement of ‘low risk’ or ‘high risk’. It is likely that the majority of studies will fall into this category.
Other bias Bias due to problems not covered elsewhere in the table.
Criteria for a judgement of ‘low risk’ of bias	The study appears to be free of other sources of bias.
Criteria for the judgement of ‘high risk’ of bias	There is at least one important risk of bias. For example, the study: had a potential source of bias related to the specific study design used; or has been claimed to have been fraudulent; or had some other problem.
Criteria for the judgement of ‘unclear risk’ of bias	There may be a risk of bias, but there is either: insufficient information to assess whether an important risk of bias exists; or insufficient rationale or evidence that an identified problem will introduce bias.

Figure 1

Study flow diagram

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Figure 2

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Figure 3

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Analysis 1.1

Comparison 1 Dietary fibre (all study interventions) versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 1.2

Comparison 1 Dietary fibre (all study interventions) versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 1.3

Comparison 1 Dietary fibre (all study interventions) versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 1.4

Comparison 1 Dietary fibre (all study interventions) versus control, Outcome 4 Number of participants diagnosed with colorectal cancer.

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Analysis 2.1

Comparison 2 Wheat bran fibre versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 2.2

Comparison 2 Wheat bran fibre versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 2.3

Comparison 2 Wheat bran fibre versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 3.1

Comparison 3 Wheat bran fibre and low fat diet versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 4.1

Comparison 4 Wheat bran fibre with or without low fat diet versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 4.2

Comparison 4 Wheat bran fibre with or without low fat diet versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 4.3

Comparison 4 Wheat bran fibre with or without low fat diet versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 5.1

Comparison 5 Comprehensive dietary intervention versus control, Outcome 1 Number of participants with at least one recurrent adenoma (4 years).

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Analysis 5.2

Comparison 5 Comprehensive dietary intervention versus control, Outcome 2 Number of participants with at least one recurrent adenoma (8 years).

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Analysis 5.3

Comparison 5 Comprehensive dietary intervention versus control, Outcome 3 Number of participants with more than one adenoma (4 years).

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Analysis 5.4

Comparison 5 Comprehensive dietary intervention versus control, Outcome 4 Number of participants with more than one adenoma (8 years).

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Analysis 5.5

Comparison 5 Comprehensive dietary intervention versus control, Outcome 5 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 6.1

Comparison 6 Ispaghula husk versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 6.2

Comparison 6 Ispaghula husk versus control, Outcome 2 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 6.3

Comparison 6 Ispaghula husk versus control, Outcome 3 Number of participants with at least one adverse effect.

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Analysis 7.1

Comparison 7 Sensitivity analysis 1. Dietary fibre (all study interventions) versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 7.2

Comparison 7 Sensitivity analysis 1. Dietary fibre (all study interventions) versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 7.3

Comparison 7 Sensitivity analysis 1. Dietary fibre (all study interventions) versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 7.4

Comparison 7 Sensitivity analysis 1. Dietary fibre (all study interventions) versus control, Outcome 4 Number of participants diagnosed with colorectal cancer.

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Analysis 8.1

Comparison 8 Sensitivity analysis 2. Wheat bran fibre versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 8.2

Comparison 8 Sensitivity analysis 2. Wheat bran fibre versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 8.3

Comparison 8 Sensitivity analysis 2. Wheat bran fibre versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 9.1

Comparison 9 Sensitivity analysis 3. Wheat bran fibre and low fat diet versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 10.1

Comparison 10 Sensitivity analysis 4. Wheat bran fibre with or without low fat diet versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 10.2

Comparison 10 Sensitivity analysis 4. Wheat bran fibre with or without low fat diet versus control, Outcome 2 Number of participants with more than one adenoma.

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Analysis 10.3

Comparison 10 Sensitivity analysis 4. Wheat bran fibre with or without low fat diet versus control, Outcome 3 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 11.1

Comparison 11 Sensitivity analysis 5. Comprehensive dietary intervention versus control, Outcome 1 Number of participants with at least one recurrent adenoma (4 years).

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Analysis 11.2

Comparison 11 Sensitivity analysis 5. Comprehensive dietary intervention versus control, Outcome 2 Number of participants with at least one recurrent adenoma (8 years).

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Analysis 11.3

Comparison 11 Sensitivity analysis 5. Comprehensive dietary intervention versus control, Outcome 3 Number of participants with more than one adenoma (4 years).

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Analysis 11.4

Comparison 11 Sensitivity analysis 5. Comprehensive dietary intervention versus control, Outcome 4 Number of participants with more than one adenoma (8 years).

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Analysis 11.5

Comparison 11 Sensitivity analysis 5. Comprehensive dietary intervention versus control, Outcome 5 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 12.1

Comparison 12 Sensitivity analysis 6. Ispaghula husk versus control, Outcome 1 Number of participants with at least one recurrent adenoma.

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Analysis 12.2

Comparison 12 Sensitivity analysis 6. Ispaghula husk versus control, Outcome 2 Number of participants with at least one adenoma 1 cm or greater.

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Analysis 12.3

Comparison 12 Sensitivity analysis 6. Ispaghula husk versus control, Outcome 3 Number of participants with at least one adverse effect.

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Summary of findings for the main comparison. Dietary fibre (all study interventions) versus control for the prevention of colorectal adenomas and carcinomas

Dietary fibre (all study interventions) versus control for the prevention of colorectal adenomas and carcinomas
Patient or population: people with a history of colorectal adenomas Settings: out‐patient setting Intervention: dietary fibre (all study interventions) versus control
Outcomes	*Illustrative comparative risks (95% CI)**		Relative effect (95% CI)	No of participants (studies)	Quality of the evidence (GRADE)	Comments
	Assumed risk	Corresponding risk
	Control	Dietary fibre (all study interventions) versus control
Number of participantswith at least one recurrent adenoma Follow‐up: 2 to 4 years	Study population		RR 1.04 (0.95 to 1.13)	3641 (5 studies)	⊕⊕⊝⊝ low^a,b
	349 per 1000	363 per 1000 (332 to 395)
	Moderate
	295 per 1000	307 per 1000 (280 to 333)
Number of participantswith more than one adenoma Follow‐up: 3 to 4 years	Study population		RR 1.06 (0.94 to 1.20)	2542 (2 studies)	⊕⊕⊝⊝ low^a,b
	250 per 1000	265 per 1000 (235 to 300)
	Moderate
	340 per 1000	360 per 1000 (320 to 408)
Number of participantswith at least one adenoma 1 cm or greater Follow up: 3 to 4 years	Study population		RR 0.99 (0.82 to 1.20)	3224 (4 studies)	⊕⊕⊝⊝ low^a,b
	102 per 1000	101 per 1000 (84 to 122)
	Moderate
	60 per 1000	59 per 1000 (49 to 72)
Number of participantsdiagnosed with colorectal cancer Follow‐up: 3 to 4 years	Study population		RR 2.70 (1.07 to 6.85)	2794 (2 studies)	⊕⊕⊝⊝ low^a,c	The incidence of colorectal cancer is very low, so when risk was calculated by risk difference (RD), the difference between groups was very small. RD = 0.01, 95% CI 0.00 to 0.01
	4 per 1000	12 per 1000 (4 to 14)
	Moderate
	5 per 1000	14 per 1000 (5 to 16)
The basis for the assumed risk* (e.g. the median control group risk across studies) is provided in footnotes. The corresponding risk (and its 95% confidence interval) is based on the assumed risk in the comparison group and the relative effect of the intervention (and its 95% CI). CI: Confidence interval; RD: Risk difference; RR: Risk ratio
GRADE Working Group grades of evidence High quality: Further research is very unlikely to change our confidence in the estimate of effect. Moderate quality: Further research is likely to have an important impact on our confidence in the estimate of effect and may change the estimate. Low quality: Further research is very likely to have an important impact on our confidence in the estimate of effect and is likely to change the estimate. Very low quality: We are very uncertain about the estimate.
^a Risk of bias: downgraded by one level due to high risk of detection/performance bias and attrition bias. ^b Indirectness: downgraded by one level as adenoma was a surrogate outcome for CRC. ^c Imprecision: downgraded by one level as the data was under powered and the sample size was below the optimal information size.

Summary of findings for the main comparison. Dietary fibre (all study interventions) versus control for the prevention of colorectal adenomas and carcinomas

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Comparison 1. Dietary fibre (all study interventions) versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	5	3641	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.95, 1.13]

2 Number of participants with more than one adenoma Show forest plot	2	2542	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.94, 1.20]

3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	4	3224	Risk Ratio (M‐H, Fixed, 95% CI)	0.99 [0.82, 1.20]

4 Number of participants diagnosed with colorectal cancer Show forest plot	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

4.1 One‐ year data	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.98 [0.36, 10.77]
4.2 Up to 4 years	2	2794	Risk Ratio (M‐H, Fixed, 95% CI)	2.70 [1.07, 6.85]

Comparison 1. Dietary fibre (all study interventions) versus control

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Comparison 2. Wheat bran fibre versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	2	1195	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.87, 1.18]

2 Number of participants with more than one adenoma Show forest plot	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.11 [0.97, 1.29]

3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.83, 1.31]

Comparison 2. Wheat bran fibre versus control

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Comparison 3. Wheat bran fibre and low fat diet versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	1	165	Risk Ratio (M‐H, Fixed, 95% CI)	1.19 [0.64, 2.18]

Comparison 3. Wheat bran fibre and low fat diet versus control

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Comparison 4. Wheat bran fibre with or without low fat diet versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	3	1360	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.88, 1.19]

2 Number of participants with more than one adenoma Show forest plot	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.11 [0.97, 1.29]

3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	2	943	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.81, 1.27]

Comparison 4. Wheat bran fibre with or without low fat diet versus control

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Comparison 5. Comprehensive dietary intervention versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma (4 years) Show forest plot	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.90, 1.12]

2 Number of participants with at least one recurrent adenoma (8 years) Show forest plot	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.78, 1.20]

3 Number of participants with more than one adenoma (4 years) Show forest plot	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.83, 1.24]

4 Number of participants with more than one adenoma (8 years) Show forest plot	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	0.89 [0.64, 1.24]

5 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.60, 1.28]

Comparison 5. Comprehensive dietary intervention versus control

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Comparison 6. Ispaghula husk versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	1.45 [1.01, 2.08]

2 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	1.80 [0.55, 5.87]

3 Number of participants with at least one adverse effect Show forest plot	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.18, 4.40]

Comparison 6. Ispaghula husk versus control

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Comparison 7. Sensitivity analysis 1. Dietary fibre (all study interventions) versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	5		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	5	3641	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.95, 1.13]
1.2 Best case scenario	5	4536	Risk Ratio (M‐H, Fixed, 95% CI)	0.61 [0.57, 0.66]
1.3 Worst case scenario	5	4536	Risk Ratio (M‐H, Fixed, 95% CI)	1.73 [1.60, 1.88]
2 Number of participants with more than one adenoma Show forest plot	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

2.1 Completers only	2	2542	Risk Ratio (M‐H, Fixed, 95% CI)	1.06 [0.94, 1.20]
2.2 Best case scenario	2	3508	Risk Ratio (M‐H, Fixed, 95% CI)	0.43 [0.38, 0.47]
2.3 Worst case scenario	2	3508	Risk Ratio (M‐H, Fixed, 95% CI)	2.48 [2.23, 2.77]
3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	4		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

3.1 Completers only	4	3224	Risk Ratio (M‐H, Fixed, 95% CI)	0.99 [0.82, 1.20]
3.2 Best case scenario	4	4335	Risk Ratio (M‐H, Fixed, 95% CI)	0.22 [0.19, 0.26]
3.3 Worst case scenario	4	4335	Risk Ratio (M‐H, Fixed, 95% CI)	4.15 [3.56, 4.85]
4 Number of participants diagnosed with colorectal cancer Show forest plot	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

4.1 One‐ year data ‐ completers only	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.98 [0.36, 10.77]
4.2 One‐ year data ‐ best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.04 [0.02, 0.11]
4.3 One‐ year data ‐ worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	41.70 [10.28, 169.08]
4.4 Up to 4 years ‐ completers only	2	2794	Risk Ratio (M‐H, Fixed, 95% CI)	2.70 [1.07, 6.85]
4.5 Up to 4 years ‐ best case scenario	2	3508	Risk Ratio (M‐H, Fixed, 95% CI)	0.05 [0.03, 0.08]
4.6 Up to 4 years ‐ worst case scenario	2	3508	Risk Ratio (M‐H, Fixed, 95% CI)	62.30 [27.32, 142.04]

Comparison 7. Sensitivity analysis 1. Dietary fibre (all study interventions) versus control

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Comparison 8. Sensitivity analysis 2. Wheat bran fibre versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	2	1195	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.87, 1.18]
1.2 Best case scenario	2	1819	Risk Ratio (M‐H, Fixed, 95% CI)	0.40 [0.35, 0.46]
1.3 Worst case scenario	2	1819	Risk Ratio (M‐H, Fixed, 95% CI)	2.46 [2.15, 2.80]
2 Number of participants with more than one adenoma Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

2.1 Completers only	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.11 [0.97, 1.29]
2.2 Best case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.28, 0.36]
2.3 Worst case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	3.34 [2.90, 3.85]
3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

3.1 Completers only	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.04 [0.83, 1.31]
3.2 Best case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	0.21 [0.17, 0.25]
3.3 Worst case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	4.78 [3.95, 5.79]

Comparison 8. Sensitivity analysis 2. Wheat bran fibre versus control

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Comparison 9. Sensitivity analysis 3. Wheat bran fibre and low fat diet versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	1	165	Risk Ratio (M‐H, Fixed, 95% CI)	1.19 [0.64, 2.18]
1.2 Best case scenario	1	201	Risk Ratio (M‐H, Fixed, 95% CI)	0.57 [0.33, 0.95]
1.3 Worst case scenario	1	201	Risk Ratio (M‐H, Fixed, 95% CI)	2.45 [1.46, 4.09]

Comparison 9. Sensitivity analysis 3. Wheat bran fibre and low fat diet versus control

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Comparison 10. Sensitivity analysis 4. Wheat bran fibre with or without low fat diet versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	3		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	3	1360	Risk Ratio (M‐H, Fixed, 95% CI)	1.03 [0.88, 1.19]
1.2 Best case scenario	3	2020	Risk Ratio (M‐H, Fixed, 95% CI)	0.41 [0.36, 0.47]
1.3 Worst case scenario	3	2020	Risk Ratio (M‐H, Fixed, 95% CI)	2.45 [2.16, 2.79]
2 Number of participants with more than one adenoma Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

2.1 Completers only	1	637	Risk Ratio (M‐H, Fixed, 95% CI)	1.11 [0.97, 1.29]
2.2 Best case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	0.31 [0.28, 0.36]
2.3 Worst case scenario	1	1429	Risk Ratio (M‐H, Fixed, 95% CI)	3.34 [2.90, 3.85]
3 Number of participants with at least one adenoma 1 cm or greater Show forest plot	2		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

3.1 Completers only	2	943	Risk Ratio (M‐H, Fixed, 95% CI)	1.02 [0.81, 1.27]
3.2 Best case scenario	2	1819	Risk Ratio (M‐H, Fixed, 95% CI)	0.20 [0.17, 0.24]
3.3 Worst case scenario	2	1819	Risk Ratio (M‐H, Fixed, 95% CI)	4.81 [4.00, 5.78]

Comparison 10. Sensitivity analysis 4. Wheat bran fibre with or without low fat diet versus control

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Comparison 11. Sensitivity analysis 5. Comprehensive dietary intervention versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma (4 years) Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.00 [0.90, 1.12]
1.2 Best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.81 [0.73, 0.90]
1.3 Worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	1.23 [1.11, 1.37]
2 Number of participants with at least one recurrent adenoma (8 years) Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

2.1 Completers only	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	0.97 [0.78, 1.20]
2.2 Best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.60 [0.50, 0.72]
2.3 Worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	1.52 [1.26, 1.84]
3 Number of participants with more than one adenoma (4 years) Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

3.1 Completers only	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	1.01 [0.83, 1.24]
3.2 Best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.64 [0.54, 0.77]
3.3 Worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	1.54 [1.28, 1.84]
4 Number of participants with more than one adenoma (8 years) Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

4.1 Completers only	1	1932	Risk Ratio (M‐H, Fixed, 95% CI)	0.91 [0.66, 1.27]
4.2 Best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.38 [0.29, 0.50]
4.3 Worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	2.05 [1.56, 2.70]
5 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

5.1 Completers only	1	1905	Risk Ratio (M‐H, Fixed, 95% CI)	0.88 [0.60, 1.28]
5.2 Best case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	0.32 [0.23, 0.44]
5.3 Worst case scenario	1	2079	Risk Ratio (M‐H, Fixed, 95% CI)	2.39 [1.75, 3.25]

Comparison 11. Sensitivity analysis 5. Comprehensive dietary intervention versus control

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Comparison 12. Sensitivity analysis 6. Ispaghula husk versus control

Outcome or subgroup title	No. of studies	No. of participants	Statistical method	Effect size
1 Number of participants with at least one recurrent adenoma Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

1.1 Completers only	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	1.45 [1.01, 2.08]
1.2 Best case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	0.78 [0.58, 1.05]
1.3 Worst case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	2.23 [1.59, 3.14]
2 Number of participants with at least one adenoma 1 cm or greater Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

2.1 Completers only	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	1.80 [0.55, 5.87]
2.2 Best case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	0.20 [0.10, 0.42]
2.3 Worst case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	8.40 [3.04, 23.20]
3 Number of participants with at least one adverse effect Show forest plot	1		Risk Ratio (M‐H, Fixed, 95% CI)	Subtotals only

3.1 Completers only	1	376	Risk Ratio (M‐H, Fixed, 95% CI)	0.90 [0.18, 4.40]
3.2 Best case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	0.08 [0.02, 0.25]
3.3 Worst case scenario	1	437	Risk Ratio (M‐H, Fixed, 95% CI)	9.65 [2.99, 31.09]

Comparison 12. Sensitivity analysis 6. Ispaghula husk versus control

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Fibra dietética para prevenir a recorrência de adenomas e carcinomas colorretais

Appendices

Appendix 1. Cochrane Library search strategy

Appendix 2. MEDLINE search strategy

Appendix 3. Embase search strategy

Appendix 4. Criteria for judging risk of bias in the 'Risk of bias' assessment tool

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Appendices

Appendix 1. Cochrane Library search strategy

Appendix 2. MEDLINE search strategy

Appendix 3. Embase search strategy

Appendix 4. Criteria for judging risk of bias in the 'Risk of bias' assessment tool

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