___________________________________________________________________________ Colorectal Cancer
respect to dietary fiber, after adjusting for age, known risk factors, and total energy intake [36]. One study evaluated the associations between dietary fiber, fat, and colorectal cancer risk in the Women’s Health Initiative prospective cohort, which included 134,017 women [37]. During a mean 11.7 years follow-up (1993–2010), 1,952 incident cases of colorectal cancer were identified. When fiber and fat intake were assessed individually, the authors found a modest trend toward lower cancer risk with increased intakes of total fiber, suggesting a mild protective effect of higher fiber intake on risk of colorectal cancer, but not when combined with intake of dietary fats [37]. Results of a pooled analysis of 3,209 participants combined from two trials indicate that men may experience more benefit
from colorectal cancer attributable to low physical activity and high BMI have increased in many geographic regions, particularly in low-middle and middle sociodemographic index regions. Countries with a higher baseline burden in 1990 and a higher sociodemographic index in 2019 had a faster decline in age-adjusted mortality rates of colorectal cancer attributed to high BMI and low physical activity [41]. Diet Among the observational study findings, patients with stage III colon cancer who had the lowest Western dietary pattern post-treatment showed significantly greater rates of disease- free survival and overall survival versus patients with highest Western dietary pattern [42; 43]. Also, patients with the highest dietary glycemic load showed significantly greater overall survival rates compared with those with the lowest dietary glycemic load. Another uncontrolled cohort study of patients diagnosed with colorectal cancer found the extent of red and processed meat ingestion was associated with a 29% greater risk of death before colorectal cancer diagnosis, but red meat ingestion after diagnosis had no effect on overall mortality [44]. Plasma Vitamin D Level There is evidence that vitamin D may be an important cofactor in immune protection against colorectal cancer risk. A large, population-based case-control study, derived from the Nurses’ Health Study and Health Professionals Follow-Up Study, found a significant association between plasma vitamin D level and colorectal cancer risk according to the degree of local antitumor immune response. The study consisted of 318 colorectal cancer cases and 624 matched controls. Subjects were divided into three groups based on the median plasma vitamin D level (tertile I 19.0 ng/mL, tertile III 37.4 ng/mL) and analyzed according to the degree of lymphocytic immune reactivity within and surrounding the tumor. Subjects in the highest vitamin D tertile were seen to have a significantly lower risk of developing colorectal cancer subtype showing an intense intratumoral cellular immune reaction. This association was not found for tumor subtypes characterized by a poor intratumoral immune response. The authors discuss possible mechanisms and conclude that these observations support a role for vitamin D in cancer immunoprevention through tumor-host interaction [45]. The National Comprehensive Cancer Network does not currently recommend routine screening for vitamin D deficiency or supplementation of vitamin D in patients with colorectal cancer. (https://www.nccn.org/professionals/ physician_gls/pdf/colon.pdf. Last accessed March 14, 2022.) Level of Evidence : 2a (Based upon lower-level evidence, there is uniform NCCN consensus that the intervention is appropriate.)
from dietary fiber than women [38]. Diet High in Fruits and Vegetables
Overall, results from more rigorously designed randomized controlled trials have washed out findings of significant correlation in earlier studies that linked higher fruit and vegetable consumption with lower rates of colorectal cancer. Diets low in fat and meat and high in fiber, fruits, and vegetables started as an adult do not appear to reduce the risk of colorectal cancer by a clinically important degree [37; 39]. Lifestyle and Diet Modification in Recurrence Risk Reduction Cohort studies have demonstrated associations between specific diet or exercise regimens with improvements in disease-specific and/or overall survival in patients following treatment for colorectal cancer, but these results have not been replicated by prospective randomized trials. When verification by more rigorous studies is absent, cohort study data should be interpreted with caution, because numerous uncontrolled variables are present that may confound the observational findings [14]. Physical Activity A meta-analysis of prospective cohort studies evaluating physical activity in patients found a 25% reduction in colorectal cancer-specific mortality associated with any amount of physical activity (vs. no activity) and a 30% reduction associated with a high amount of physical activity (vs. low amount). After colorectal cancer was diagnosed, a 26% reduction in colorectal cancer-specific mortality was associated with participation in any physical activity (vs. no activity), and a 35% reduction was associated with a high amount of physical activity (vs. a low amount) [40]. A 2022 analysis used data from the Global Burden of Disease 2019 study to analyze colorectal cancer deaths associated with low physical activity and high body mass index (BMI) [41]. The analysis included data from 1990 to 2019 at global, regional, and national levels. In 2019, colorectal cancer deaths attributed to low physical activity and high BMI were an estimated 58.7 and 85.9 per 100,000 population, respectively. Corresponding age-standardized mortality rates were 0.77 (low physical activity) and 1.07 (high BMI). Since 1990, age-adjusted mortality rates
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