Effects of different weight loss programmes on oncological outcomes following curative resection of digestive tract cancers
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Authors
Niaz, O.S.
Seabrook, M.
Niaz, T.
Ahmed, I.
Parrott, R.
Rao, A.
Issue Date
2022
Type
Published Abstract
Language
Keywords
Research Subject Categories::MEDICINE::Dermatology and venerology,clinical genetics, internal medicine::Internal medicine::Gastroenterology
Alternative Title
Abstract
Effects of different weight loss programmes on oncological outcomes following curative resection of digestive tract cancers
Monitoring Editor: Cochrane Gynaecological, Neuro-oncology and Orphan Cancer Group, Osamah S Niaz,corresponding author Max Seabrook, Talha Niaz, Irfan Ahmed, Rebecca Parrott, and Ahsan Rao
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Objectives
This is a protocol for a Cochrane Review (intervention). The objectives are as follows:
To assess the effect of different weight loss programmes on oncological outcomes following curative resection of GI tract cancers.
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Background
The World Health Organization (WHO) defines the term 'overweight' as a body mass index (BMI) of 25 and over, and 'obesity' as a BMI of 30 and over. Obesity has been rising worldwide over the last several decades (WHO 2022). In the UK, approximately one‐quarter of men and women aged 16 and above were considered obese in 2012 (Health and Social Care Information 2016). This continues to be the case in the latest available data from the UK, with 26% of adults classified as obese, and a further 36.8% as overweight (House of Commons 2022). In the United States, over two‐thirds of the adult population are overweight or obese, with more than a third of the total population categorically considered obese (Flegal 2010). The latest data from the National Health and Statistics Reports revealed that 41.9% of the adult US population were obese (Stierman 2021). Many countries across the world are experiencing similar rising rates of obesity (Stevens 2012). In the last 30 to 40 years, rates of obesity have doubled globally (Ataey 2020). In 2016, the number of obese men and women were 31 and 69 million, respectively (NCD Risk Factor Collaboration 2017). The WHO reports that in 2016 39% of adults were overweight and a further 31% were obese across the world (WHO 2021). It is estimated that the proportion of worldwide obesity and overweight people will reach nearly 60% this year (WHO 2022). Globally in 2017, a BMI over 25 accounted for approximately 4.72 million deaths and 148 million attributable disability‐adjusted life‐years (DALYs) (GBD Collaborators 2018).
Obesity is associated with a variety of diseases, such as diabetes, hypertension, multiple cancers, and with an increased rate of all‐cause mortality (Flegal 2013). Higher BMIs are associated with an increased risk of a wide variety of cancers, including upper and lower gastrointestinal (GI), endometrial, thyroid, breast, leukaemias, and lymphomas (Renehan 2008). Furthermore, other parameters of obesity, such as abdominal obesity, have been shown to significantly increase the risk of certain cancers, including colon and rectal cancers (Dong 2017).
Obesity is a known risk factor for many GI cancers of varied origin (Karczewski 2019). Gastrointestinal cancers include oesophageal, stomach cardia, pancreas, gallbladder, liver, colon, and rectum. These cancers are 50% more prevalent in the overweight population (Lauby‐Secretan 2016). Moreover, the risk of cancer appears to increase in a dose‐dependent response, with the risk ratio of these GI cancers rising to 1.8 times in obese people (Lauby‐Secretan 2016). This dose‐response of cancer risk associated with an increasing BMI has also been shown in recent meta‐analyses involving multiple cancer types (Choi 2018).
Obesity poses a risk for people undergoing a cancer resection and has been shown to increase the risk of major complications, with an odds ratio of 2.1 (Euro Surg Collaborative 2018). Laparoscopic surgery may be more challenging from a surgical perspective, due to an increased difficulty manoeuvring instruments in people with higher BMIs, which in turn may increase the complexity of the operation (Fung 2017). Obese people undergoing lower‐GI cancer resections have also been shown to have a higher risk of postoperative complications, such as morbidity, infection, and anastomotic leak (Fung 2017).
An increased risk of recurrence, morbidity, and mortality has been shown amongst obese people following curative cancer resection (Mengardo 2018). This is further demonstrated by a higher risk of node metastasis in patients with high BMIs. (Fleming 2009). This leads to an approximately doubled risk of mortality following curative resections in pancreatic cancer (Fleming 2009).
In certain cancers, weight loss may reduce the risk of recurrence in obese people. There is increased support for weight loss programmes in obese people undergoing cancer resection. For example, bariatric surgery in people with breast cancer has shown to be well‐tolerated and may reduce recurrence (Zhang 2020). However, further studies are required to ascertain the long‐term benefits, overall and disease‐free survival of weight loss programmes after a cancer resection. Moreover, it is important to understand the impact on outcomes of different weight loss programmes for people following digestive tract cancer resection.
It has been hypothesised that long‐term weight loss strategies may provide improved morbidity and mortality outcomes for people who have undergone cancer resection surgery. This is in part due to the association between obesity and cancer (Anderson 2021). In a recent cohort study, lifestyle modifications have proven to be a viable avenue for weight loss in cancer survivors who have been shown to lose up to 3.9% of their body weight (Christie 2021). This suggests in theory improved outcomes when considering that an increased BMI has been shown to increase the risk of all‐cause morbidity in people undergoing rectal cancer resection within 30 days postoperatively (Hirpara 2021). However, not all studies show improved outcomes with lower BMI after GI cancer resections, and a higher BMI has been shown to have a protective effect (Rodrigues 2021). Whilst many studies suggest improved outcomes after intentional weight reduction, others have shown that bariatric surgery prior to colorectal cancer resection may not yield similar benefits (Bell 2019; Tao 2017). This illustrates the need for a literature review on the outcomes of digestive tract cancer resections and comparing the effects of different weight loss programmes.
The effect of obesity on lower GI cancers appears to contribute to a worse prognosis of these patients (Siegel 2010). It is estimated that there may be a 30% to 70% increased risk of certain lower GI cancers amongst men, whilst a less consistent association is seen with women (Bardou 2013). Moreover, obesity may be associated with poorer cancer outcomes, which may be related to less favourable metabolic profiles, such as decreased insulin resistance and metabolic syndrome (Bardou 2013). However, there is some controversy regarding upper GI cancer outcomes in obese patients, as there may be no significant difference in their oncological outcomes compared with those without obesity (Struecker 2017). The need therefore arises to investigate the effects of weight loss programmes in different GI cancers following curative resection, as there may be a greater benefit in certain GI cancer locations and types.
Weight loss and a reduction in BMI have shown improved outcomes for people following cancer resections. However, there are various methods of weight loss programmes, with no clear review of the literature comparing the different programmes available. In particular, the role of bariatric surgery has not been compared with the alternatives. There are numerous programmes utilised such as caloric restriction, dietary alterations, exercise programmes, pharmacological means, and bariatric surgery. A review is therefore essential to compare the effects of different weight loss programmes on outcomes for different digestive tract cancer resections.
Description of the condition
Recurrence rates of GI cancers after resection remain high (Böckelman 2015). For certain cancers, such as colorectal cancer, recurrence rates may be as high as 82% without adjuvant chemotherapy (Böckelman 2015). Other studies have shown the recurrence rate of colorectal cancer after an intended curative surgery to be approximately 45% (Wilhelmsen 2014). For oesophagogastric cancers, after an intended curative resection, the recurrence rate by five years has been shown to be up to 85%, with major contributing factors being age and severity of the cancer (Youn 2010). Liver and gallbladder cancers also show a high recurrence rate, for example in cholangiocarcinoma recurrence rates are between 49% and 64% after curative resection (Blechacz 2017).
There is significant morbidity and mortality associated with cancer recurrence following intended curative resections. In cholangiocarcinoma there is less than a 20% chance of long‐term survival (Blechacz 2017). Recurrence is associated with a high risk of mortality related to cancer and therefore it is pertinent to determine factors that may improve outcomes after a cancer resection (Ryuk 2014). It has been hypothesised that weight loss programmes may play a beneficial role in improving these outcomes.
Description of the intervention
Weight loss programmes pertain to any programme that aims to reduce the BMI of people by any extent, usually with an overall goal of achieving a normal weight (e.g. a BMI between 20 and 25). However, in much higher levels of obesity (BMI over 40), a reduction to a less severe level may be the goal. The types of weight loss programmes vary significantly and include lifestyle changes, pharmacology, and surgical procedures. The National Institute for Health and Care Excellence (NICE) advises lifestyle changes as the first means of weight loss programme (NICE 2014).
Lifestyle changes may include nutrition counselling, dietary food changes, dietary caloric restriction, and exercise. Pharmacological agents may be used as part of weight loss programmes, usually with lifestyle changes, and include noradrenergic agents, gastrointestinal lipase inhibitors, serotonin agonists, metformin, zonisamide, pramlintide, liraglutide, and naltrexone‐bupropion (Yanovski 2014). Bariatric surgery is another type of weight loss programme that may be used as an adjunct to other types of weight loss programmes. Common procedures include Roux‐en‐Y gastric bypass, sleeve gastrectomy, biliopancreatic diversion with duodenal switch, adjustable gastric banding, intermittent vagal blockades, and swallowable gastric balloons (Wolfe 2016).
Weight loss surgery is increasing in popularity, with nearly half a million bariatric operations carried out globally in 2013 (Angrisani 2015). Various bariatric techniques are utilised around the world with Roux‐en‐Y gastric bypass being the most common worldwide (45%), followed by the sleeve gastrectomy (37%) and adjustable gastric banding (10%) (Angrisani 2015). Bariatric surgeries have been shown to have long‐term success, demonstrating an average 30 kg, or 22% total weight loss (O'Brien 2019). Moreover, new, minimally invasive techniques including the endoscopic sleeve gastroplasty have been shown to be safe and effective weight loss strategies worldwide (Singh 2020).
Weight loss interventions prior to surgery appear to reduce the cancer mortality rate (Ma 2017). There are currently limited studies directly investigating bariatric surgery prior to cancer resection and its associated survival rates; however, in the case of breast cancer, excess body weight is related to worse survival outcomes (Zhang 2020). It should be noted that many cancers requiring surgical resection would unlikely benefit from a time‐delay for bariatric or lifestyle intervention, and there remain limited data investigating this directly. In breast cancer patients, more studies have investigated postresection interventions (Zhang 2020). Whilst bariatric surgery is well tolerated in people with breast cancer, studies are still ongoing and are needed to assess the benefit on cancer outcomes (Zhang 2020). It was recently shown that breast and endometrial cancer patients who underwent bariatric surgery after their cancer diagnosis experienced improved cancer survival outcomes (Lee 2022). It is therefore important to investigate which GI cancers may benefit from weight loss programmes and, if so, when the interventions should take place.
How the intervention might work
Weight loss is associated with lower rates of GI tract‐related cancers and is therefore hypothesised to have beneficial outcomes in people after a GI tract cancer resection. However, there are paradoxical findings where there is an increased survivability in people with a higher BMI in cancer resections (Anderson 2021). Studies have highlighted the importance of investigating weight loss programmes with regard to improving survival outcomes after a GI cancer resection. This is in part due to the anecdotal evidence of people doing well postresection after intentional weight loss (Anderson 2021).
Weight loss programmes, particularly those pertaining to low‐fat diets, may be associated with a relative reduction of all‐cause mortality by 18% (Ma 2017). Bariatric surgery has also been investigated for its potential risk reduction of cancer and may be associated with a reduced cancer risk amongst morbidly obese individuals, although there appears to be a disparity amongst studies (Casagrande 2014). Nevertheless, in a recent meta‐analysis it appears that bariatric surgery yielded a significant risk reduction in cancers associated with obesity at a population level (Wiggins 2019).
People with a normal BMI who undergo cancer resection have been shown to have improved oncological outcomes in certain GI cancers. This may be in part due to more favourable metabolic conditions of the patient such as improved insulin resistance and obesity‐related inflammation (Siegel 2010).
Why it is important to do this review
There are conflicting reports on weight loss regarding morbidity and mortality following GI tract cancer resection (Anderson 2021; Wilhelmsen 2014). In certain cancers, a higher BMI has been shown to improve outcomes; however, there is limited knowledge on current trends relating to weight loss programmes following GI tract cancer resection. This review will therefore detail the currently available evidence on this topic and help guide areas for further research. In particular, the role of bariatric surgery is rising worldwide, and it is important to review its benefits in comparison to conventional weight loss programmes.
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Objectives
To assess the effect of different weight loss programmes on oncological outcomes following curative resection of GI tract cancers.
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Methods
Criteria for considering studies for this review
Types of studies We will review randomised controlled trials that assess the effect of weight loss strategies on oncological outcomes of non‐metastatic digestive tract cancers (upper gastrointestinal, colorectal, and hepatobiliary) following curative resection.
Types of participants Adults over the age of 18 with hepatobiliary, colorectal, or upper gastrointestinal cancer who have undergone curative resections for primary non‐metastatic tumours.
Types of interventions Weight loss interventions will broadly include the following.
Lifestyle changes, including dietary calorie restriction, exercise, nutrition counselling, and dietary food changes.
Pharmacological means, including noradrenergic agents, gastrointestinal lipase inhibitors, serotonin agonists, metformin, zonisamide, pramlintide, liraglutide, and naltrexone‐bupropion.
Bariatric surgery, including Roux‐en‐Y gastric bypass, sleeve gastrectomy, gastric balloons, and other less common procedures.
Weight loss programmes in the above population are varied and may also be utilised in conjunction with other methods. These may include nutrition education, which involves changing the psychology around eating, as well as exercise programmes of varying intensity (e.g. the 'balance' programme, which aims for slow and steady weight loss, versus the 'fast' programme, which aims for rapid weight loss within three months) (NHS 2022).
In a certain subset of people these exercise/diet regimens are unsuccessful, hence bariatric surgery is undertaken. The most commonly used procedures in the UK are the Roux‐en‐Y gastric bypass and the sleeve gastrectomy. Other, less used procedures include the mini bypass or gastric band.
We will review studies comparing weight loss programmes in comparison to a placebo or current standards of care.
Types of outcome measures
Primary outcomes
Overall mortality
Local recurrence
Distant recurrence
Secondary outcomes
Disease‐free survival
Quality of life
Overall complication rate
Time to recurrence
Search methods for identification of studies
There will be no restrictions based on the language or status of the publication. A combination of MeSH and free‐text terms will be used in different electronic databases to retrieve appropriate studies for the review. The search strategy will include all kinds of GI cancers and the effect of weight loss following curative cancer resection.
Electronic searches A Cochrane Information Specialist will search the databases mentioned below to identify relevant publications.
The Cochrane Central Register of Controlled Trials (CENTRAL; latest issue), in the Cochrane Library;
MEDLINE via Ovid (MEDLINE Epub Ahead of Print, In‐Process & Other Non‐indexed Citations, MEDLINE Daily, and MEDLINE; 1946 onwards);
Embase via Ovid (1980 onwards);
CINAHL EBSCO (Cumulative Index to Nursing and Allied Health Literature; 1982 onwards).
The MEDLINE search strategy is presented in Appendix 1. We will adapt this strategy to the other databases.
Searching other resources We will review the references of identified studies and contact the authors of relevant studies.
We will also contact experts in the field regarding unpublished data. We will review the abstracts published from the international conferences on GI malignancy and evaluate any potentially relevant studies. These conferences include but are not limited to: Association of Surgeons of Great Britain and Northern Ireland (ASGBI), Association of Surgeons in Training (ASiT), and the European Society of Surgical Oncology (ESSO).
Data collection and analysis
Selection of studies Three review authors (ON, MS, TN) will independently perform study selection. After removal of any duplicate publications, the review authors will assess the abstracts remaining from the search for potential relevance. We will obtain the full‐text articles for abstracts considered potentially relevant, and the review authors will evaluate the full‐text articles for inclusion in the review, excluding any articles that do not meet the inclusion criteria. Any disagreements will be escalated to the supervising author (AR).
We will list studies that were excluded after initially meeting our inclusion criteria and the reasons for their exclusion in a table. We will display the publication selection process in a PRISMA diagram.
Data extraction and management Three review authors (ON, MS, TN) will review data from each included study. We will record the data obtained from the included publications on data collection forms as advised in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2022).
We will pay particular attention to data on patient demographics, tumour pathology, tumour staging, type of operation, type of weight loss programme, duration of weight loss programme, number of sessions of weight loss programme, type of bariatric operation or surgery, duration of follow‐up, oncological outcome, and mortality. We will also include time‐to‐event outcomes such as five‐year overall mortality, five‐year overall survival, five‐year disease‐free survival, time to local recurrence, and time to distal recurrence.
For studies with multiple reports, we will review each report individually and sum up the data onto one form.
We will organise the data via a Microsoft Excel spreadsheet (Microsoft Corporation 2018). We will perform data analysis using Review Manager 5 (Review Manager 2020).
Assessment of risk of bias in included studies Two review authors (TN, MS) will independently evaluate the included studies for risk of bias using Cochrane's risk of bias tool (RoB 2), as described in the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2022). We will assess risk of bias based on the following domains.
From the randomisation process
Due to variations from the intervention
Due to missing outcome data
Associated with the measurement of the outcomes
Associated with the results selected
We will subsequently grade each of the domains above as:
low risk;
high risk; or
some concerns.
We will summarise our findings in a risk of bias table using the Microsoft Excel template available at www.riskofbias.info/welcome/rob-2-0-tool/current-version-of-rob-2.
Measures of treatment effect We will present the measures of treatment effect for dichotomous data using risk ratio (RR) with 95% confidence intervals (CI).
For continuous variables, we will assess the outcome for each participant measured from baseline before interventions are administered. This allows for the possibility of analysing these data based on 'change score' (Higgins 2021).
We will assess the mean difference (MD) of the change of score between different groups and will represent this with a 95% confidence interval (Higgins 2021). Moreover, for each arm we will note n (number of participants), mean, and standard deviation (SD). If the scale of an outcome differs, we will the standardised mean difference (SMD) rather than the MD.
Unit of analysis issues The unit of analysis will be the individual participant who is randomised to each group.
Dealing with missing data We will record any missing data on our data collection form. In the first instance, we will contact the study authors to request missing data. If we receive no response, we will evaluate the data missing due to participant dropout using an intention‐to‐treat analysis (ITT).
Assessment of heterogeneity We will assess heterogeneity using the I2 statistic, as per the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2021). We will interpret the results as follows:
0% to 40%: heterogeneity might not be important;
30% to 60%: moderate heterogeneity;
50% to 90%: substantial heterogeneity;
75% to 100%: considerable heterogeneity.
Assessment of reporting biases We aim to use a well‐organised and strong search strategy. In the case of unpublished trials, we will attempt to incorporate their data. We will also use funnel plots for the main outcomes of the study to assess publication bias. We will use funnel plots to assess reporting bias for meta‐analyses including 10 or more studies. We will also assess for language bias in only those studies that showed significant results.
Data synthesis We will pool data from studies that are analogous using Review Manager 5 software (Review Manager 2020). We will use a random‐effects model as we expect variation in outcomes and study size. We will use the generic inverse variance method for continuous variables and Mantel‐Haenszel method for dichotomous variables.
Subgroup analysis and investigation of heterogeneity We plan to carry out the following subgroup analyses.
Effect of bariatric surgery versus non‐operative weight loss programmes on overall mortality.
Effect of weight loss on hepatobiliary versus upper gastrointestinal versus colorectal cancers.
Sensitivity analysis We will carry out sensitivity analysis to assess the robustness of the results, in particular if there are studies with high risk of bias and notable assumptions.
Summary of findings and assessment of the certainty of the evidence We will display the results of our meta‐analyses using a summary of findings table. We will include the following outcomes in the summary of findings table.
Overall mortality
Local recurrence
Distant recurrence
Disease‐free survival
Quality of life
Overall complication rate
Time to recurrence
We will assess the certainty of the evidence according to the five GRADE principles (risk of bias, consistency of effect, imprecision, indirectness, and publication bias), as recommended in Chapter 14 of the Cochrane Handbook for Systematic Reviews of Interventions (Higgins 2021). Based on the aforementioned principles, we will subcategorise the data into four levels of certainty (high, moderate, low, or very low). We will justify any decisions to downgrade the certainty of the evidence using footnotes to aid the reader's understanding of the review.
A template for a summary of findings table is provided in Appendix 2.
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Acknowledgements
We thank Jo Morrison from Cochrane Gynaecological, Neuro‐oncology and Orphan Cancers (GNOC) for clinical advice. We also thank Gail Quinn and Tracey Harrison for their contribution to the editorial process and Jo Platt for designing the search strategy.
The authors and Cochrane Gynaecological, Neuro‐oncology and Orphan Cancers Team are grateful to the following peer reviewers for their time and comments: Andrew Bryant, Richard Edmondson, Sarah Kitson, and Richard Welbourn.
We would like to acknowledge the library at Princess Alexandra Hospital for helping us with the initial literature search for the concept of the review.
This project was supported by the National Institute for Health Research (NIHR), via Cochrane infrastructure funding to the Cochrane Gynaecological, Neuro‐oncology and Orphan Cancers Group. The views and opinions expressed therein are those of the review authors and do not necessarily reflect those of the Systematic Reviews Programme, NIHR, NHS, or the Department of Health.
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Appendices
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Appendix 1. MEDLINE search strategy
1. exp Weight Loss/
2. exp Weight Reduction Programs/
3. (weight adj5 (cyc* or reduc* or los* or maint* or decreas* or watch* or control* or gain* or chang* or manage* or plan* or program* or diet*)).mp.
4. exp obesity/
5. exp Overweight/
6. exp weight gain/ or exp weight loss/
7. exp body mass index/
8. (overweight* or over weight* or excess weight* or obes*).mp.
9. 1 or 2 or 3 or 4 or 5 or 6 or 7 or 8
10. exp Exercise/
11. exp Exercise Therapy/
12. exp Exercise Movement Techniques/
13. Physical Fitness/
14. exp Physical Endurance/
15. exp Muscle Strength/
16. (exercis* or resistance* or movement* or stretch* or aerobic* or anaerobic* or flexibility*).ti,ab.
17. ((physical* or resistance*) adj3 (activ* or therap* or exercise* or endurance* or education* or fitness* or train*)).ti,ab.
18. ((balance* or coordination* or strength*) adj3 (train* or exercise*)).ti,ab.
19. 10 or 11 or 12 or 13 or 14 or 15 or 16 or 17 or 18
20. 9 or 19
21. exp Digestive System Surgical Procedures/
22. (gastrectom* or gastrojejunostom* or colectom* or esophagectom* or oesophagectom*).mp.
23. ((digest* or esophag* or oesophag* or gastro‐intestin* or gastrointestin* or mucosal or endoscopic* or GI or UGI or low anterior or colon* or bowel* or stomach or rectal or gastric* or bariatric* or weight‐los*) adj5 (resect* or surg* or procedur*)).mp.
24. exp Bariatric Surgery/
25. 21 or 22 or 23 or 24
26. exp Digestive System Neoplasms/
27. ((esophag* or oesophag* or HPB or UGI or upper GI or stomach or gastric or colorectal opr CRC or bowel or colon or rectal or hepatobiliary or pancrea* or liver or hepatocellular or gastrointestinal or gastroesophageal or intestinal or cecal or duodenal or ileal or jejunal or adenomatois or colonic or anus or sigmoid or colitis) adj5 (neoplasm* or cancer* or tumor* or tumour* or carcinoma* or malignan*)).mp.
28. 26 or 27
29. 25 and 28
30. 20 and 29
31. randomized controlled trial.pt.
32. controlled clinical trial.pt.
33. randomized.ab.
34. placebo.ab.
35. clinical trials as topic.sh.
36. randomly.ab.
37. trial.ti.
38. 31 or 32 or 33 or 34 or 35 or 36 or 37
39. 30 and 38
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Appendix 2. Draft summary of findings table
The effect of different weight loss programmes on the oncological outcomes following curative resection of digestive tract cancers (upper gastrointestinal, colorectal, and hepatobiliary)
Patient or population: people with non‐metastatic digestive tract cancers who have undergone curative resection
Intervention: weight loss strategy
Comparison: standard treatment
Outcomes Illustrative comparative risks* (95% CI) Relative effect
(95% CI) No. of participants
(studies) Certainty of the evidence
(GRADE) Comments
Assumed risk Corresponding risk
With weight loss programme Without weight loss programme
Overall mortality
Local recurrence
Distal recurrence
Disease‐free survival
Quality of life
Overall complication rate
Time to recurrence
*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; RR: risk ratio
GRADE Working Group grades of evidence
High certainty: we are very confident that the true effect lies close to that of the estimate of the effect.
Moderate certainty: we are moderately confident in the effect estimate: the true effect is likely to be close to the estimate of the effect, but there is a possibility that it is substantially different.
Low certainty: our confidence in the effect estimate is limited: the true effect may be substantially different from the estimate of the effect.
Very low certainty: we have very little confidence in the effect estimate: the true effect is likely to be substantially different from the estimate of effect.
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Notes
New
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Contributions of authors
ON: first author, led review process including protocol writing and prospective study selection and data analysis.
MS: protocol writing, prospective study selection and data analysis.
TN: protocol writing, prospective study selection and data analysis.
IA: helped conceptualise idea and will monitor progress and critically review and advise at all stages
RP: protocol writing, prospective study selection and obtaining full texts of studies.
AR: supervising author, initiated the idea for the review, ensuring work is carried out at an appropriate pace, and helping guide authors with all steps of the review.
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Sources of support
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Internal sources
No sources of support provided
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External sources
There are no external sources of support in terms of funding for the review, Other
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Declarations of interest
ON: none known
MS: none known
TN: none known
IA: none known
RP: none known
AR: none known
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References
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Description
Citation
Niaz OS, Seabrook M, Niaz T, Ahmed I, Parrott R, Rao A. Effects of different weight loss programmes on oncological outcomes following curative resection of digestive tract cancers. Cochrane Database Syst Rev. 2022 Oct 31;2022(10):CD015146. doi: 10.1002/14651858.CD015146. PMCID: PMC9621105.