Obesity may increase the risk of colorectal cancer in women

Women with a BMI of 30 kg / m² or more have shown an increased risk of early-onset colorectal cancer, according to data from the upcoming ongoing Nurses' Health Study II.

"In contrast to declining trends among adults aged 50 and over, incidence and mortality from colorectal cancer have increased in all age groups between 20 and 49 years of age",

Po-Hong Liu, MD, MPH,
researcher at Massachusetts General Hospital and Harvard Medical School, as well as his colleagues. "The causes of increased incidence of early colorectal cancer have not been elucidated. The increasing prevalence of established risk factors for colorectal cancer, such as obesity, sedentary lifestyle, Western diet and diabetes, may contribute to this. "

Liu and colleagues used data from Nurses' Health Study II to assess associations between BMI and early colorectal cancer in 85,256 nurses aged 25 to 42 years.

During follow-up, during 1,196,452 person-years, the researchers observed 114 cases of early-onset colorectal cancer. The median age at diagnosis was 45 years old.

Compared with women who had a BMI of 18.5 kg / m² at 22.9 kg / m², the risk of colorectal cancer at an early stage was higher in women considered overweight with a BMI of 25 kg / m² at 29.9 kg / m² (RR = 1.37, 95% CI, 0.81-2.3) and women considered obese with a BMI of 30 kg / m² or higher (RR = 1.93, 95% CI, 1.15-3.25).

Each 5-fold increase in BMI appeared to be associated with an RR of 1.2 (95% CI, 1.05-1.38; P for trend = .01).

Researchers have observed similar associations between women with no family history of colorectal cancer and women who have not undergone lower endoscopy in the last 10 years.

When assessing BMI at age 18, women whose BMI was 21 kg / m² at 22.9 kg / m² had a RR of 1.32 (95% CI, 0.8-2.16) and those with a BMI of 23 kg / m² or more had an RR of 1.63 (95% CI, 1.01-2.61) compared to women with a BMI of 18.5 kg / m² at 20.9 kg / m².

Compared to women under 5 kg or having lost weight since the age of 18, women from 20 kg to 39.9 kg had a RR of 1.65 (95% CI, 0.96 2.81) and women 40 kg or older had a RR of 2.15 (95% CI, 1.01 to 4.55; P for trend = 0.007).

"The biological mechanisms underlying the association between obesity and colorectal cancer remain unclear," the researchers wrote. "The metabolic syndrome, insulin resistance, systemic inflammation, and immunity are important mediators. Microbial dysbiosis may also contribute. "

PAGE BREAK

The limitations of the study included the lack of data on waist and hip measurements, as well as the inclusion of predominantly white women.

"Since most of these younger cases are symptomatically diagnosed with more advanced tumors and with a significant influence on the years of life lost, our results reinforce the benefits of maintaining a healthy weight throughout life," the researchers wrote. . "Our results suggest the possibility of using body weight to personalize and supplement early detection strategies for cancer in adults under 50 years of age." – by Cassie Homer

Disclosures: Liu does not report any relevant financial information. An author reports consultant fees from Bayer, Janssen and Pfizer.