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Obesity-Related Cancers Rising in Young Adults in the United States

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Key Points

  • Incidence increased for 6 of the 12 obesity-related cancers (colorectal, uterine corpus [endometrial], gallbladder, kidney, multiple myeloma, and pancreas) in young adults and in successively younger birth cohorts in a stepwise manner.
  • The risk of colorectal, uterine corpus [endometrial], pancreas, and gallbladder cancers in millennials is about double the rate baby boomers had at the same age.
  • Rates in successive younger birth cohorts declined or stabilized in all but two of 18 nonobesity-related cancers, including smoking-related and infection-related cancers.

A new study has found rates are increasing for 6 of 12 cancers related to obesity in younger adults in the United States, with steeper increases in progressively younger ages and successively younger generations. The study, published by Sung et al in The Lancet Public Health, also looked at rates for 18 cancers unrelated to obesity—and found rates increasing for only 2.

The obesity epidemic over the past 40 years has led to younger generations experiencing an earlier and longer-lasting exposure to excess adiposity over their lifetime than previous generations. Excess body weight is a known carcinogen, associated with more than a dozen cancers and suspected in several more. Exposures to carcinogens during early life may have an even more important influence on cancer risk by acting during crucial developmental periods.

Several years ago, the authors of the current study identified increases in early onset colorectal cancer in the U.S., a trend that has been observed in several high-income countries and could partly reflect the obesity epidemic. For the new study, they extended that analysis by examining recent age-specific trends in 30 types of cancers, including 12 known to be associated with obesity.

Study Methods and Findings

Investigators led by Hyuna Sung, PhD, analyzed 20 years of incidence data (1995–2014) for 30 cancers in 25 states from the Cancer in North America database provided by the North American Association of Central Cancer Registries, covering 67% of the population of the U.S.

Incidence increased for 6 of the 12 obesity-related cancers (colorectal, uterine corpus [endometrial], gallbladder, kidney, multiple myeloma, and pancreas) in young adults and in successively younger birth cohorts in a stepwise manner. For example, the risk of colorectal, uterine corpus [endometrial], pancreas, and gallbladder cancers in millennials is about double the rate baby boomers had at the same age. In contrast, rates in successive younger birth cohorts declined or stabilized in all but two of 18 nonobesity-related cancers, including smoking-related and infection-related cancers.

“Although the absolute risk of these cancers is small in younger adults, these findings have important public health implications,” said Ahmedin Jemal, DVM, PhD, Scientific Vice President of Surveillance & Health Services Research at the American Cancer Society and senior/corresponding author of the paper. “Given the large increase in the prevalence of overweight and obesity among young people and increasing risks of obesity-related cancers in contemporary birth cohorts, the future burden of these cancers could worsen as younger cohorts age, potentially halting or reversing the progress achieved in reducing cancer mortality over the past several decades. Cancer trends in young adults often serve as a sentinel for the future disease burden in older adults, among whom most cancer occurs.”

The authors say innovative strategies are needed to mitigate morbidity and premature mortality associated with obesity-related diseases, primarily by health-care providers and policymakers.

Statement From ASCO President Monica M. Bertagnolli, MD, FACS, FASCO, on New Findings on Obesity and Cancer

“Rates of obesity-related cancers are rising most sharply among young adults, but this study should serve as a wake-up call to all Americans—young and old alike—that obesity is linked to an increased risk of common cancers. If current trends continue, it is estimated that obesity will lead to more than 500,000 additional cases of cancer each year in the United States by 2030.”

“Obesity is set to overtake tobacco as the leading cause of preventable cancer-related death, and there is an alarming lack of awareness among the American public of the link between obesity and cancer. ASCO’s 2018 National Cancer Opinion Survey found that while 80% of Americans know that smoking cigarettes is a risk factor for cancer, only 35% realize that obesity is a major risk factor too.”

“We need to educate people of all ages that obesity is a risk factor for cancer and inform them of the steps they can take to decrease the likelihood of developing the disease. ASCO provides resources to help physicians educate and care for their patients on the importance of maintaining a healthy weight. The Society also shares information on obesity and cancer through its medical meetings, patient website Cancer.Net, journals, and other avenues.”

“In addition, more research is needed to address the obesity epidemic in our country and understand its relationship to various cancers. Just this past week ASCO, issued its first-ever set of Research Priorities to Accelerate Progress Against Cancer. Among the priorities, ASCO identified the reduction of obesity and its impact on cancer incidence and outcomes as a critical area on which to focus future research efforts.”

“We must also recognize that the obesity epidemic and cancer is not just a crisis in the U.S., but a global one.”

Disclosure: The study authors' full disclosures can be found at thelancet.com.

The content in this post has not been reviewed by the American Society of Clinical Oncology, Inc. (ASCO®) and does not necessarily reflect the ideas and opinions of ASCO®.


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