Hisham Hussan, MD
Obesity is associated with an increased risk of early-onset colorectal cancer (CRC) among women and correlates with higher rates of cancer resections in gastrointestinal (GI) malignancies across age groups, according to recent research findings.
In findings published in JAMA Oncology,
investigators reported that the risk for developing CRC before age 50 years is nearly double for women who are obese and elevated for those who are overweight compared with women with a normal body mass index (BMI).1
Meanwhile, rates of resection were higher among obese patients with CRC as well as gastric, pancreatic, and esophageal cancers than they were for nonobese patients and, in some of these GI cancer types, were increasing more rapidly, investigators reported at the 2018 American College of Gastroenterology (ACG) Annual Meeting.2
The latest study findings in GI cancers come at a time of increasing concern over the role that obesity plays in multiple tumor types. In an analysis published earlier this year, American Cancer Society researchers said that excess body weight accounts for the second-highest proportion of cancer cases and deaths attributable to potentially modifiable risk factors after cigarette smoking.3
At the same time, epidemiologists have been noting with alarm that younger people are increasingly likely to be diagnosed with GI malignancies. In colon cancer, overall incidence and mortality have been declining since the 1980s; however, population-based projections suggest colon cancer incidence is expected to increase by 90% among adults aged 20 to 34 years and by 28% among those aged 35 to 49 years by 2030. The incidence of rectal cancer is expected to increase by 124% among those aged 20 to 34 years and by 46% among those aged 35 to 49 years.1
Incidence of early-onset CRC, defined as diagnoses in adults younger than 50 years, remains rare at approximately 8 per 100,000 individuals, but accounts for at least 10% of total CRCs that are not prevented or detected through screening.1
Body Mass Characterized
To date, investigators have not been able to identify the factors contributing to the increase in early-onset disease. Led by epidemiologists at Washington University School of Medicine in St. Louis, Missouri, investigators sought to examine the association between obesity, weight gain, and CRC. They analyzed data from the Nurses’ Health Study II, an ongoing study of female nurses (N = 85,256) in the United States who were free of cancer and inflammatory bowel disease when they enrolled in the study in 1989. The findings showed that the risk for developing CRC before age 50 years is nearly double for women who were obese, defined as a BMI ≥30.0, compared with those with a BMI of 18.5 to 22.9.
Compared with women who had a BMI of 18.5 to 22.9, the relative risk (RR) for early-onset CRC was 1.93 (95% CI, 1.15-3.25) for obese women and 1.37 (95% CI, 0.81-2.30) for overweight women. The RR for women with a BMI of 23.0 to 24.9 was 1.33 (95% CI, 0.75-2.36). Investigators observed a direct correlation between higher BMI and increased risk. The RR for every 5-unit increase in BMI was 1.20 (95% CI, 1.05-1.38; P
= .01 for trend).
Cosenior author Yin Cao, ScD, a cancer epidemiologist and assistant professor of surgery in the Division of Public Health Sciences at Washington University in St. Louis, estimated that 22% of early-onset CRCs could be prevented if all women in the study had a BMI between 18.5 and 24.9.
“Our findings really highlight the importance of maintaining a healthy weight, beginning in early adulthood, for the prevention of early-onset colorectal cancer,” she said in a statement. “We hypothesized that the obesity epidemic may partially contribute to this national and global concern in early-onset colorectal cancer rates, but we were surprised by the strength of the link and the contribution of obesity and weight change since early adulthood.”
In this observational study, investigators detected 114 cases of early-onset disease during nearly 1.2 million person-years of follow-up. The median age at diagnosis was 45 years (interquartile range, 41-47). Women in the study were disease free at enrollment and aged from 25 to 42 years. Participants were followed from 1989 through 2011.
Women with a higher current BMI tended to be older and less likely to engage in physical activity. These women also consumed more red meat and were more likely to have diabetes, and their current BMI correlated with the BMI at age 18 (Pearson correlation coefficient, 0.55).