Veronica Hackethal, MD
September 11, 2019
Obesity has been linked to an increased risk for at least 13 types of cancers. A new study has found that these types of cancers may be increasing disproportionately among younger people in the United States.
During the past 17 years, new diagnoses of obesity-associated cancers increased particularly among those aged 50–64 years, while rates of new diagnoses decreased among those aged 65 years or older. In the past, obesity-associated cancer developed more commonly among older individuals.
The shift in obesity-associated cancers was even more pronounced among racial and ethnic minorities, with black and Hispanic women and men experiencing the highest percentage increase.
"Our study indicates that it is critically important for physicians to fully evaluate cancer symptoms even in younger patients, especially when they are obese," author Siran M. Koroukian, PhD, told Medscape Medical News via email.
The findings highlight the need for individualized screening and interventions for fighting obesity.
"Physicians should urge young patients to maintain normal weight because obesity promotes or accelerates cancer. The literature suggests that obesity-associated cancers in younger patients may be more aggressive and present at more advanced stages, requiring more intensive therapy," she emphasized.
The study was published online on August 14 in JAMA Network Open.
The findings have important public health implications, with particular relevance to primary care physicians and oncologists, she added.
"The increase in cancer in younger people who are at the height of their productive years means lost economic potential and premature mortality," she said.
"Cancer survivorship comes with increased physical and mental comorbidity burden, as well as financial toxicity. Consequently, public programs such as Medicare and Medicaid will be greatly impacted by this shift," she added.
Rising in Younger People
The authors note that data from the Centers for Disease Control and Prevention suggest that overweight or obesity contributed to 40% of cancers diagnosed in 2014. The increase in these types of cancers, combined with increasing rates of obesity in younger age groups, raised the question of whether cancer rates are rising in younger people.
To investigate the issue, the team analyzed data for January 2000 to December 2016 from the National Cancer Institute's Surveillance, Epidemiology, and End Results (SEER) database, which is representative of the US population and includes about 97% of new cancer cases diagnosed in surveyed regions. Researchers evaluated change in cancer burden over time, categorized by age, sex, and race/ethnicity.
The analysis included 2,665,574 new obesity-associated cancer diagnoses (70.3% of which were in women) and 3,448,126 new nonobesity associated cancer diagnoses (32.0% of which were in women). The study excluded Alaskan natives, persons younger than age 20 years, and men with breast cancer.
Obesity-associated cancers included colorectal cancer; female breast cancer; cancer of the uterus and gallbladder and other biliary cancers; cancer of the esophagus, stomach, liver, intrahepatic bile duct, pancreas, ovary, kidney, and renal pelvis; cancer of the thyroid; and myeloma.
The analysis showed a shift in the age distribution of new diagnoses of obesity-associated cancers during the past 17 years, with the greatest increase among individuals aged 50–64 years. Among this age group, the combined number of new diagnoses of all obesity-associated cancers increased by 197.8%, compared to 93.9% for those aged 20–49 years and 91% for those older than 65 years.
Among persons in younger age groups, there was also a higher likelihood that annual rates of new cases of obesity-associated cancer would outstrip cancers not related to obesity. This likelihood was highest among non-Hispanic white men aged 20–49 years (ratio of odds ratios [ORs], 1.020; 95% confidence interval, 1.018 – 1.022).
The opposite was true for the group aged 65 years or older, with greater odds that annual rates of new cancers not associated with obesity would be higher than those associated with obesity, regardless of race/ethnicity (range ratio of ORs, 0.983 – 0.996).
Although incidence rates for obesity-associated cancers generally decreased over this period among those aged 65 and over, the total number of new cases increased. This finding was most likely due to individuals who aged into this group from the younger age group, according to the authors.
New diagnoses of obesity-associated cancer disproportionately affected racial/ethnic minorities. Hispanic men aged 50–64 experienced the greatest percent increase (197.8%), while non-Hispanic white women in this age group experienced the least increase (25.3%).
Likewise, certain types of obesity-associated cancers increased disproportionately among racial/ethnic minorities. For example, Hispanic women aged 50–64 experienced about a 400% increase in thyroid cancer and more than a 200% increase in melanomas and kidney, uterine, and pancreatic cancers.
The authors mentioned several limitations of their study, including lack of data on poverty, racism, smoking, genetic mutations, family history of cancer, and environmental factors that could contribute to cancer. Also, the SEER data lacked information on body fatness, so the researchers could not determine whether people who were overweight or obese were the ones who developed cancer.
Nevertheless, in a press release, senior author Nathan A. Berger, MD (Case Comprehensive Cancer Center, Case Western Reserve University School of Medicine, Cleveland, Ohio), concluded:
"We all know that public health education efforts are important to address the impact of obesity on individuals' health and quality of life. This analysis of the SEER data proves the point at a population level, with dramatic findings for the Black and Hispanic communities. Public health practitioners and officials are wise to continue and even increase efforts to inform people about the adverse consequences of obesity, and support individuals and communities in changing behaviors that contribute to obesity."
The study was funded by a National Cancer Institute–designated Case Comprehensive Cancer Center and Case Comprehensive Cancer Center Cancer Disparities SPORE planning grant. Koroukian and coauthor Weichuan Dong, MA, received support through contracts from the Cleveland Clinic Foundation, including a subcontract from the Celgene Corporation. The other authors have disclosed no relevant financial relationships.