Evidence shows that diets high in red and processed meat are associated with an increased risk of colorectal cancer. In a study reported in the Journal of Clinical Oncology, Marjorie L. McCullough, ScD, Strategic Director of Nutritional Epidemiology, and colleagues from the Epidemiology Research Program of the American Cancer Society examined the association between pre- and postdiagnosis red/processed meat consumption and all-cause and colorectal cancer–specific mortality.1 They found that high prediagnosis consumption was associated with increased all-cause mortality and mortality from cardiovascular disease but not colorectal cancer mortality and that high postdiagnosis consumption was not associated with all-cause or cause-specific mortality.
Study Details
Participants in the Cancer Prevention Study II Nutrition Cohort reported information on diet and other factors at baseline in 1992 to 1993, 1999, and 2003. Participants with a colorectal cancer diagnosis after baseline and up to June 30, 2009, were observed for mortality through December 31, 2010.
A total of 2,315 participants were diagnosed with invasive nonmetastatic colorectal cancer. Subjects had a mean age of 73 years at diagnosis and approximately 55% were male. Red/processed meat intake by quartile at baseline was a mean of 1.5 servings per week in the 1st (bottom) quartile, 3.8 per week in the 2nd quartile, 6.0 per week in the 3rd quartile, and 10.4 per week in the 4th (top) quartile.
Effect of Prediagnosis Diet
In the analysis of prediagnosis diet, a total of 966 patients with colorectal cancer died during an average follow-up of 7.5 years, including 413 from colorectal cancer, 176 from cardiovascular disease, and 377 from all other causes combined. In multivariable analysis adjusting for age at diagnosis, sex, tumor stage, prediagnosis energy intake, body mass index, history of diabetes, and history of myocardial infarction, greater red/processed meat intake before colorectal cancer diagnosis was associated with greater risk (top vs bottom quartile) of death from all causes (relative risk [RR] = 1.29, 95% confidence interval [CI] = 1.05–1.59, P = .03 for trend).
The multivariable analysis also revealed greater prediagnosis red/processed meat intake to be associated with higher risks of death from cardiovascular disease (RR = 1.63, 95% CI = 1.00–2.67, P = .08 for trend) and death from all other causes (RR = 1.39, 95% CI = 1.00–1.92, P = .08 for trend), but not death from colorectal cancer (RR = 1.09, 95% CI = 0.79–1.51, P = .54 for trend).
Effect of Postdiagnosis Diet
In the analysis of postdiagnosis diet, 472 deaths occurred during a mean follow-up of 7.6 years, including 146 from colorectal cancer, 110 from cardiovascular disease, and 216 from other causes. Quartiles of red/processed meat intake varied according to year of survey.
On multivariate analysis adjusting for age at diagnosis, sex, tumor stage, and postdiagnosis energy intake, greater red/processed meat consumption (top vs bottom quartile) after colorectal cancer diagnosis was not independently associated with all-cause mortality (RR = 1.02, 95% CI = 0.761.38, P = .90 for trend), colorectal cancer–specific mortality (RR = 1.28, 95% CI = 0.74–2.21, P = .46 for trend), cardiovascular disease mortality (RR = 0.88, 95% CI = 0.47–1.64, P = .48 for trend), or mortality from all other causes (RR = 0.94, 95% CI = 0.60–1.46, P = .76 for trend).
Effect of Change in Intake
In multivariate analyses of changes in intake before and after diagnosis, patients with high intake (median or above) both before and after diagnosis had increased risk of death from colorectal cancer (RR = 1.79, 95% CI = 1.11–2.89) compared with those with low intake before and after. Patients with low intake before and high intake after diagnosis had increased risk of death from other causes (RR = 1.62, 95% CI = 1.06–2.48). Patients with high intake before and low intake after diagnosis had increased risk of all-cause mortality (RR = 1.37, 95% CI = 1.02–1.85). A low intake after diagnosis may have been due to illness.
No significant interactions were found between prediagnosis or postdiagnosis red/processed meat intake and total mortality (top vs bottom quartile) stratified by sex, tumor stage, colon or rectum site of disease, or body mass index. A borderline significant interaction was observed for prediagnosis intake and family history of colorectal cancer (RR = 2.87 for family history, 95% CI 1.28-6.43, P = .05). A post hoc analysis showed no association between intake and survival among patients with metastatic disease.
The investigators concluded: “[H]igh red and processed meat intake before a diagnosis of [colorectal cancer] was associated with a greater risk of death, a finding driven mainly by death as a result of causes other than [colorectal cancer]. Our findings, which underscore the importance of a long-term healthy diet with limited red and processed meat intake, are relevant because cancer survivors in general are at greater risk of chronic diseases such as heart disease compared with the general population.” ■
Disclosure: Dr. McCullough reported no potential conflicts of interest.
Reference
1. McCullough ML, Gapstur SM, Shah R, et al: Association between red and processed meat intake and mortality among colorectal cancer survivors. J Clin Oncol. July 1, 2013 (early release online).
