For most cancers, risk is higher if you are older. Yet, increasingly, cancers are being diagnosed at younger ages. While there are likely several reasons this is happening, researchers say one important contributor is the increasing prevalence of obesity in young people.
New research that reviewed existing cancer and obesity incidence data suggests increased rates of obesity are causing more cases of obesity-related cancers in young adults (in this research, defined as those under 50). A major conclusion of the paper was that many of the malignancies found to occur with increasing frequency in young adults are among the 13 obesity-associated cancers.
Additionally, the researchers looked at animal studies that investigated how obesity mechanistically changes how cancer cells grow and found that, in the obesity-related cancers (including breast cancer, colon cancer, multiple myeloma, renal cell carcinoma, endometrial cancer, and thyroid cancer, among others) obesity actually accelerates the rate of cancer growth in animal models compared with the rates of cancer growth in non-obese animal models. The findings were published online ahead of print in the journal Obesity (2018; doi.org/10.1002/oby.22137).
"This prospect, in association with the worldwide expansion of obesity, suggests an impending explosive increase in obesity-associated cancers in young adults," the study authors noted in the paper.
The research reviewed data from more than 100 existing preclinical, clinical, and epidemiological studies that investigated cancer incidence and the effect of obesity on cancer development, including potential mechanisms.
In an interview with Oncology Times, study author Nathan Berger, MD, of Case Western Reserve University, School of Medicine, explained why these findings are significant and the next steps of the research. Berger is the Hanna-Payne Professor of Experimental Medicine; Director of the Center for Science, Health and Society; and Professor of Medicine, Biochemistry and Oncology, all at Case Western.
1 This review showed that obesity accelerates the growth of certain cancers-not just the incidence. Can you explain how this is different than previous reports?
"Previous studies have shown that obesity increases the risk for cancer-and that obesity makes cancer worse. That means if you have cancer and you're obese your prognosis is worse than if you're not obese.
"There are several different models where it's quite clear that obesity accelerates the onset of cancers.
"[Our research team had previously done] a lot of translational work with animal models and with people. When the reports started coming out about the increase in young adult cancers, we noticed that many of those were among the obesity-associated cancers. So, we reviewed the obesity-associated cancers in young adults. We reviewed the reports of increased cancers in young adults and we reviewed the animal models [of cancer growth rates]. And we reviewed the SEER and other population-based cancer data to come up with the observations that we reported.
"In the manuscript, we talk about how obesity accelerates the development of myeloma; obesity accelerates the development of renal cell carcinoma; and obesity has been shown to accelerate the development of breast cancer. It's been shown to speed of the development of thyroid cancer, pancreatic cancers, colon cancer, [and] multiple myeloma-and we think it's probably across the board for all the types of cancer that are associated with obesity."
2 What would you say are the implications of these findings?
"The key finding from our work is that there is a marked increase in obesity associated with this increased cancer in young adults. And based on our analysis, particularly in animal models, we've shown that obesity accelerates the development of cancer.
"The important thing is the young adult cancers and cancers associated with obesity [are] sometimes more aggressive and you need to keep that in mind. When you have an obese young person with cancer or an obese person with cancer, you need to remember that the disease can be more aggressive, so you have to treat the disease very aggressively. And you have to do your best to get the patient to lose weight.
"It used to be that a lot of oncologists felt that the cancer treatment was going to be so stressful that you should not advise the patient to try and lose weight. I think it's just the opposite. You need to advise the patient to lose weight and exercise more."
3 What's the next step of your research?
"One of the things we're interested in doing is to better define the mechanisms [that accelerate the growth of cancer in individuals who are obese], which will help us develop strategies to prevent obesity and related cancers.
"The other thing is we think the preliminary evidence suggests that the obesity promotion of cancer probably involves epigenetics, among other factors, so we're trying to document these epigenetic effects and also identify drugs and lifestyles that may modify the epigenetic effects."