Western and prudent dietary patterns have been associated with higher and lower risks of colorectal cancer, respectively.
However, little is known about the associations between dietary patterns and specific anatomic subsites or molecular subtypes of colorectal cancer.
Dr Andrew Chan and colleagues from Massachusetts, USA used multivariable Cox proportional hazards models to examine the associations between Western and prudent dietary patterns and colorectal cancer risk in the Health Professionals Follow-up Study and Nurses’ Health Study.
After up to 32 years of follow-up of 137,217 men and women, the researchers documented 3260 cases of colorectal cancer.
Among individuals from whom subsite data were available, the team observed 1264 proximal colon, 866 distal colon, and 670 rectal tumors.
|Western diet appears more strongly associated with some colorectal cancer molecular subtypes in 39% of cases|
The team found that a Western diet was associated with an increased incidence of colorectal cancer, with a relative risk of 1.3.
The researchers noted that the association of Western diet with colorectal cancer was evident for tumors of the distal colon, and rectum but not proximal colon when comparing extreme quartiles.
In contrast, for the prudent pattern, the team observed a relative risk of 0.86 for overall colorectal cancer, with similar trends at anatomic subsites.
However, the trend appeared stronger among men than women.
The researchers found that 39% of cases with tissue available for molecular profiling, Western diet appeared to be more strongly associated with some colorectal cancer molecular subtypes, although formal tests for heterogeneity did not produce statistically significant results.
Dr Chan's team concludes, "Western dietary patterns are associated with an increased risk of colorectal cancer, particularly distal colon and rectal tumors."
"Western dietary patterns also appear more strongly associated with tumors that are KRAS wildtype, BRAF wildtype, have no or a low CpG island methylator phenotype, and microsatellite stability."
"In contrast, prudent dietary patterns are associated with a lower risk of colorectal cancer that does not vary according to anatomic subsite or molecular subtype."