Obesity Is Risk Factor for Colorectal Cancer Recurrence: A Systematic Review and Meta-Analysis: 299

INTRODUCTION: There is a wealth of epidemiologic evidence supporting the association between weight parameters and colorectal cancer incidence. However, how these variables affect colorectal cancer (CRC) recurrence is still a topic of debate. In our study, we hypothesized that there would be increased risk of recurrence of colorectal cancer with obesity and higher visceral fat. METHODS: A systematic review of electronic databases was performed through April 2019, including NCBI, Embase, Cochrane, and Web of Science. Screening was performed using Covidence and each article was screened independently by two authors. Included were retrospective and prospective studies reporting CRC outcomes of at least 2 months after cancer diagnosis. The primary outcome was CRC recurrence in obese compared to normal weight subjects, and high vs. normal visceral fat. Weight parameters tested were body mass index (BMI) categories of underweight, normal, overweight, and obese; visceral fat as measured by CT scan into categories of normal and high visceral fat. Odds ratios (OR), risk ratios (RR), and 95% confidence intervals (95% CI) are reported. Random effects analysis was performed for all outcomes, with heterogeneity assessed by the I 2 statistic. RESULTS: 484 citations were reviewed of which 9 were included in the final analysis. In total, 7 studies analyzed CRC recurrence data in terms of BMI, and 2 in terms of visceral adiposity. Most were retrospective cohort studies. These studies comprised 5777 patients, with an average age of 61.4 years and with mean follow-up time of 58.4 months, range (52 months–77 months). Both overweight and obese BMI were associated with significantly increased risk of cancer recurrence compared to normal BMI individuals (Figure 1), OR 1.41 (95% CI 1.18–1.69), P = 0.00, I 2 = 0%, N = 4295, and OR 1.47 (95% CI 1.02–2.12), P = 0.04, I 2 = 45%, N = 3637, respectively. There was no association between being underweight and colorectal cancer recurrence compared to normal BMI or overweight BMI. High visceral adiposity was also not associated with increased CRC recurrence, although only two studies were included in our meta-analysis (Table 1). CONCLUSION: Obese and overweight BMI are both associated with increased risk of CRC recurrence compared to normal weight. However, being underweight was not associated with CRC recurrence compared to being normal weight. Patients with CRC would likely benefit from active interventions to prevent obesity.