As the obesity crisis continues, more young people face the specter of obesity-related cancers. Incidence rates for six malignancies linked to obesity are rising more sharply in successively younger age groups, according to a recent study, and experts say that could threaten the progress made in the fight against cancer.
Multiple cancers are associated with excess weight, the National Cancer Institute reports. These include cancers of the thyroid, breast (in postmenopausal women), kidney, liver, gallbladder, endometrium, ovary, and colon and rectum.
Now evidence is building that obesity-related cancers are increasingly affecting people at younger ages. In a study published in JNCI: Journal of the National Cancer Institute last year, Ahmedin Jemal, DVM, PhD, Vice President of the Surveillance and Health Services Research Program at the American Cancer Society (ACS), and other researchers reported an increase in colorectal cancer incidence rates among young adults in the United States, despite a decline in overall incidence rates for colorectal cancer. The group found a decrease in incidence rates in older adults due to colonoscopy, according to Jemal.
“Our study showed rates increasing in younger adults until age 55,” he says. “We thought it may be related to obesity because obesity is one risk factor among many for colorectal cancer.”
That suspicion prompted Jemal and a separate group of ACS researchers to investigate whether early-onset disease was on the rise in other obesity-related cancers.
A Stepwise Increase
Jemal and his team gathered data on more than 14 million cases involving 30 cancer types — 18 of the 20 most common cancers and 12 obesity-associated cancers — from a database of the North American Association of Central Cancer Registries. The cancers were diagnosed in patients 25–84 years of age from 1995 to 2014. The researchers categorized patients into 15 partly overlapping 10-year birth cohorts from 1915 to 1985.
They found that for six obesity-related cancers — multiple myeloma and cancers of the endometrium, gallbladder, kidney, pancreas, and colon and rectum — incidences in younger adults increased, and the incidence rate increases were steeper in successively younger five-year age groups.
“There was a dose-response relationship,” Jemal says. “As age decreased, the rate of increase in the incidence rates increased [in a] stepwise fashion.”
That surprised the researchers, who had not expected to see such a marked association between decreasing age and increasing incidence rates in so many obesity-related cancers. For certain cancers, including endometrial, colorectal and pancreas, millennials’ incidence rates were nearly twice as high as baby boomers’ had been at the same age. Incidence rates in all but two of the 18 non-obesity-related cancers declined or held steady in successively younger groups, likely due to a decline in risk factors, such as smoking and certain infections, including HIV, that are associated with some of those cancers. The study appeared in The Lancet Public Health.
Portents of Trouble
Jemal says if the trends his group’s study describes continue, progress researchers and clinicians have made in combating cancer may come to a halt. He is not alone in that concern.
“[W]ith the increasing obesity pandemic worldwide, it means we’re going to be seeing a lot of cancer at a much earlier age, and we’re going to have all of the comorbidities associated with cancer,” says Nathan Berger, MD, Hanna-Payne Professor of Experimental Medicine and Distinguished University Professor at Case Western Reserve University in Cleveland, who was not involved with Jemal’s study. “We’re going to have a lot more very critically ill young people. A lot of these cancers in young people are getting diagnosed late, so they’re much harder ... and more expensive to treat. [Cancer] is going to be affecting people who should be in their prime in terms of raising a family and [contributing] in the workforce.”
Kenneth Carson, MD, PhD, Assistant Professor in the Department of Medicine, Oncology Division, Medical Oncology at Washington University School of Medicine in St. Louis, believes progress in the realms of early detection and more effective cancer treatments could be overwhelmed by higher incidences. Dr. Carson, who was not involved in the study, says that necessitates rethinking medicine’s current approach to obesity prevention and management in young people.
“[T]he guidelines and recommendations and having a physician say, ‘You know, you really need to lose weight,’ aren’t moving the needle,” Dr. Carson says. “[Obesity] is a very difficult disease to combat, so it may require drastic measures like bariatric surgery in order to make real headway.”