Poor diet quality linked to increased risk for early-onset colorectal cancer precursors
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A poor-quality diet appeared associated with an increased risk for early-onset, high-risk distal and rectal adenomas, according to study results published in Journal of the National Cancer Institute.
“These findings provide preliminary but strong support to the role of diet in early-onset colorectal cancer,” Yin Cao, MPH, ScD, researcher in the division of public health sciences of the department of surgery at Washington University School of Medicine in St. Louis, and colleagues wrote. “The role of poor diet quality in the rising incidence of colorectal cancer diagnosed [among those aged younger than 50 years] has not been explored. Based on molecular features of early-onset colorectal cancer, early-onset adenomas are emerging surrogate endpoints.”
In their comprehensive analysis of the prospective cohort Nurses’ Health Study II, investigators assessed the effect of two dietary patterns — Western and prudent — and three recommendation-based indexes — Dietary Approaches to Stop Hypertension (DASH), Alternative Mediterranean Diet (AMED) and Alternative Healthy Eating Index 2010 (AHEI-2010) — on the risk for early-onset colorectal cancer, using early-onset adenomas and those of high malignant potential as surrogate endpoints.
The analysis included 29,474 women who underwent at least one lower endoscopy before age 50 years between 1991 and 2011.
Researchers obtained data on anatomical location, size and histology of adenomas, as well as number of polyps. High-risk adenomas included those with any of the following characteristics: size of at least 1 cm, tubulovillous/villous histology, high-grade dysplasia or the presence of at least three adenomas. The investigators categorized all other adenomas as low risk.
Results showed women who had a higher Western dietary pattern score, indicating high consumption of red and processed meats, were less likely to exercise or use multivitamins and more likely to have a greater number of pack-years of smoking. Conversely, women more adherent to the prudent dietary pattern and DASH, AMED and AHEI-2010 were more likely to demonstrate healthier behaviors.
Of the 1,157 early-onset adenomas identified among all women, 375 were considered high-risk.
Researchers observed inverse associations between risk for early-onset adenoma and the prudent diet, DASH, AMED and AHEI-2010, whereas as a positive association was found with the Western diet. The associations mostly were confined to high-risk adenomas, with ORs of 1.67 (95% CI, 1.18-2.37) for the Western diet, 0.69 (95% CI, 0.48-0.98) for the prudent diet, 0.65 (95% CI, 0.45-0.93) for DASH, 0.55 (95% CI, 0.38-0.79) for AMED and 0.71 (95% CI, 0.51-1.01) for AHEI-2010.
High-risk adenomas appeared most likely to occur in the distal colon and rectum (all P trend .04), but not among those with higher AMED scores.
“The slightly different associations based on dietary index classification system might inspire future work exploring the specific mechanisms involved,” Cao and colleagues wrote. “More detailed studies of differences in dietary index adherence and colorectal cancer risk by anatomic site in youth are also warranted.”
Researchers acknowledged possible residual confounding and dietary measurement errors as study limitations.
A major strength of the study was the availability of regularly updated dietary intake data collected over 20 years. As a result, longer-term dietary intake patterns should be better captured than with a single dietary assessment commonly used in other studies, according to an editorial accompanying the study by Neil Murphy, PhD, and Marc J. Gunter, PhD, both researchers in the section of nutrition and metabolism at the International Agency for Research on Cancer in Lyon, France, and Peter T. Campbell, PhD, researcher in the department of population science at American Cancer Society.
“That said, due to the convenience of adenomas as a more frequently occurring surrogate endpoint, to what extent these findings inform on the role of diet in early-onset colorectal cancer development is not certain,” they wrote. “[Although] colorectal adenomas can lie on the causal pathway of colorectal tumorigenesis, most colorectal adenomas do not progress to carcinomas. In addition, it is unknown what proportion of early-onset adenomas in the study would have become carcinomas before age 50 years.”
Given that incidence of early-onset colorectal cancer is estimated to increase by more than 140% by 2030, identifying preventable risk factors for early-onset carcinomas is a high priority, they added.
“Consequently, we and others have initiated the Colorectal Cancer Pooling Project [C2P2], an international pooling effort of more than 25 prospective cohort studies, to comprehensively interrogate potential risk factors and biomarkers for colorectal cancer diagnosed in people in different age groups,” they wrote. “The establishment of the C2P2 infrastructure offers a promising pathway for future epidemiological studies to unravel the etiology of early-onset colorectal cancer.”
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For more information:
Yin Cao, MPH, ScD, can be reached at Washington University School of Medicine, 660 S. Euclid Ave., Campus Box 8100, St. Louis, MO 63110; email: yin.cao@wustl.edu.
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