The relationship between body mass index and short term postoperative outcomes in patients undergoing potentially curative surgery for colorectal cancer: A systematic review and meta-analysis

Highlights

• Obesity was associated with a significantly higher risk of developing surgical site infection following surgery for colorectal cancer in both Asian and Western population.

• The risk of superficial/wound infection was greater in obese patients, however, there was still a significant association between obesity and deep/organ space infection.

• Further studies are needed to define the magnitude of this risk with increasing obesity.

Abstract

Background

The prevalence of obesity has increased worldwide over the last few decades, and is a well-recognized risk factor for colorectal cancer. Surgical site infection is the most frequent complication following surgery for colorectal cancer, and the main cause of postoperative morbidity. The aim of the present systematic review and meta-analysis was to examine the relationship between increasing BMI and postoperative surgical site infection following surgery for colorectal cancer.

Methods

A systemic literature search was conducted using Medline, PubMed, Embase (Ovid) and Web of Science databases from inception to the end of August 2016. Studies examining the relationship between obesity and surgical site infection following surgery for colorectal cancer were included. Analysis of the data was performed using Review Manager version 5.3(The Nordic Cochrane Centre, The Cochrane Collaboration, Copen-hagen, Denmark,)

Results

In this meta-analysis, a total of 9535 patients from 16 studies were included. BMI <30 vs ≥30 kg/m² was used to examine the association of obesity and surgical site infection in patients from Western countries. The estimated pooled OR demonstrated that obesity increased the risk of surgical site infection by approximately 100% (OR = 2.13; 95% CI 1.66-2.72, p < 0.001).BMI <25 vs ≥25 kg/m² was used to examine the association of obesity and surgical site infection from Asian countries. The estimated pooled OR demonstrated that obesity increased the risk of surgical site infection by approximately 60% (OR = 1.63; 95% CI 1.29-2.06, p < 0.001). There was little evidence of publication bias in the meta-analysis.

Conclusion

From this systematic review and meta-analysis there was good evidence that obesity was associated with a significantly higher risk of developing surgical site infection following surgery for colorectal cancer in both ethnic groups. The magnitude of the effect warrants further investigation.

Introduction

The global prevalence of obesity has increased steadily over recent decades and continues to rise (World Health Organisation, 2015). In the United Kingdom, the prevalence of obesity increased from 15% in 1993 to 26% in 2014 (HSCIC, Health and Social Care Information Centre, 2016). The WHO defines overweight, as a body mass index (BMI) of 25–29·9 kg/m², while BMI of 30.00–34.99 kg/m² is defined as obese grade I, with obese grade II as BMI 35.00–39.99 kg/m² and obesity grade III as BMI ≥40.00 kg/m². However, the prevalence of obesity by using the WHO definition is variable across different populations. For example: the prevalence of obesity using BMI ≥30 kg/m² is less than 10 % in East Asian populations (Park et al., 2010). In addition, the incidence of obesity related disorder such as dyslipidemia, hyperglycemia and hypertension was higher at BMI > 25.0 kg/m². Therefore, the International Obesity Task Force (IOTF) has recommended a BMI threshold of 25.0 kg/m² for obesity in these populations.

Nevertheless, obesity is a well-established risk factor for the development of several chronic diseases, such as diabetes, heart disease, and certain cancers, such as colorectal cancer. Indeed, a large scale study in the UK with 5.24 million subjects (Bhaskaran et al., 2014) found statistically significant associations between increased BMI and 17 of the 22 most frequent cancers including colorectal cancer. Each 5 kg/m² increase in BMI was associated with a higher risk of cancer of the colon and rectum of approximately 10% and 5% respectively (Bhaskaran et al., 2014). There is also good evidence that obesity is an important risk factor of death from colorectal cancer. A recent meta-analysis by Doleman and coworkers (Doleman et al., 2016) showed that, compared with normal weight patients, obese patients with colorectal cancer (BMI > 30 kg/m²) had an increased relative risk of all-cause mortality and cancer specific mortality of approximately 15%.

In colorectal cancer, surgical resection remains the primary treatment, and resection may be associated with appreciable morbidity and mortality. Surgical site infection (SSI) is the most frequent group of complications amongst colorectal surgery patients with an incidence of up to 38% (Konishi et al., 2006). It is associated with increased cost of treatment, longer hospital stay and occasionally leads to mortality (Smith et al., 2004).

Despite considerable attention to both the increasing prevalence of obesity and the frequent occurrence of surgical site infection after colorectal surgery, the data regarding the impact of increased BMI on surgical site infection after colorectal surgery is conflicting. For example, some researchers have reported an increased risk of surgical site infection in obese patients (Zhou et al., 2012), while others have reported no such association (Mrak et al., 2012). Such discrepancies in the literature may well reflect lack of statistical power. Therefore, the aim of the present systematic review and meta-analysis was to examine the relationship between increasing BMI and surgical site infection following surgery for colorectal cancer.