From the Journals

Obesity, weight gain linked to colorectal cancer risk in younger women



Obesity and weight gain are linked to increased risk of colorectal cancer in younger women, according to an analysis of a large, prospective U.S. cohort study.

Young women who were obese had a nearly twofold increase in risk of early-onset colorectal cancer, compared with women of normal weight, authors of the study reported in JAMA Oncology.

The findings suggest body weight could be used to “personalize and complement” early cancer screening strategies among adults younger than 50 years, said investigator Po-Hong Liu, MD, of Washington University, St. Louis, and coauthors.

“Given that most of these younger cases are diagnosed symptomatically with more advanced tumors and with a significant influence on years of life lost, our findings reinforce the benefits of maintaining a healthy weight throughout life,” Dr. Liu and coinvestigators said in their report.

Their analysis was based on the ongoing Nurses Health Study II, which began in 1989 and enrolled a total of 116,430 women between the ages of 25 and 42 years in 14 U.S. states. Women completed questionnaires on demographics, medical and health information, and lifestyle factors every 2 years after enrollment.

Dr. Liu and colleagues were able to document 114 cases of colorectal cancer over a median of 13.9 years of follow-up in 85,256 women who had no cancer or inflammatory bowel disease when they were enrolled in the study. The median age at diagnosis for these cancers was 45 years.

Obesity was independently associated with increased risk of these early-onset colorectal cancers, the investigators found in multivariable analysis.

Women with a body mass index of 30 kg/m2 or higher had a relative risk of 1.93 (95% confidence interval, 1.15-3.25) versus women with normal BMIs in the 18.5-22.9 kg/m2 range, according to results of the analysis, they reported.

There was an apparent linear trend between increasing weight and increasing colorectal cancer risk, they added in their report.

They also found links between BMI in early adulthood and risk of early-onset colorectal cancer, including a relative risk of 1.63 for women who reported a BMI of 23 kg/m2 or higher at 18 years of age, versus women with a BMI of 18.5-20.9 kg/m2 at that age.

Similarly, increase in weight since early adulthood was associated with increased cancer risk, they reported.

While the link between excess weight and colorectal cancer incidence and mortality is well established in previous studies, this study is one of few reports looking at the association in younger individuals, according to Dr. Liu and colleagues.

This is thought to be the first prospective study looking at the link between obesity and risk of colorectal cancer diagnosed before the age of 50, they added.

The study was funded by grants from the National Institutes of Health. Dr. Liu had no conflict of interest disclosures related to the study. One coauthor reported consulting fees from Bayer Pharma AG, Janssen, and Pfizer.

SOURCE: Liu P-H et al. JAMA Oncol. 2018 Oct 11. doi: 10.1001/jamaoncol.2018.4280.

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