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Obesity-related cancers increasing in younger adults

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Obesity-cancer link gaining plausibility

Cancer was long thought of as a disease of aging, but the increase in incidence of some cancers in younger age groups has driven a recent reexamination of risk factors. This study’s most striking finding is the disproportionate increase in obesity-related cancer incidence among successively younger cohorts. Coupled with the rising incidence of obesity over the same period, it provides compelling evidence of a possible causal role for obesity in the increased incidence of these cancers.

Not all obesity-related cancers, however, show this pattern of age-specific increase in incidence, which could reflect the influence of other risk factors.

The hypothesis suggested by the study’s authors is plausible but needs to be tested more directly in experimental and population-based studies.

Catherine R. Marinac, PhD, is with the department of medical oncology at the Dana-Farber Cancer Institute, Boston, and Brenda M. Birmann, ScD, is with the department of medicine at Brigham and Women’s Hospital, Boston. These comments are taken from an accompanying editorial (Lancet Public Health. 2019 Feb 4. doi: 10.1016/S2468-2667(19)30017-9). No conflicts of interest were declared.


 

FROM THE LANCET PUBLIC HEALTH


For pancreatic cancer, significant annual increases in incidence were seen among individuals aged 25-29 years (4.34%) and 30-34 years (2.47%).

The study also showed increases in the same obesity-related cancers – except for colorectal cancer – among adults aged 50 years and older. The incidence of colorectal cancer actually decreased annually in older adults, while the incidence of uterine corpus cancer increased among women aged 50-69 years but decreased in those over 75 years.

Dr. Sung and her coauthors suggested that these trends may be related to the rise of obesity and overweight in the United States, noting that excess body weight could be responsible for up to 60% of all endometrial cancers, 36% of gallbladder cancers, and 33% of kidney cancers in adults aged over 30 years.

“Because most epidemiological studies have primarily focused on older populations, the effect of excess bodyweight in early life or of weight change from young adulthood on cancer risk in different stages of the life course is not well characterized,” they wrote. “In concert with excess bodyweight, obesity-related health conditions and lifestyle factors can contribute to the increasing burden of obesity-related cancers in young adults, which include diabetes, gallstones, inflammatory bowel disease, and poor diet.”

The incidences of breast cancer and gastric cardia cancer were relatively stable in all age groups over the study period, and the incidence of ovarian cancer decreased in all age groups.

Researchers looked at the incidence of 30 cancers in total, including 18 cancers not related to obesity. Here they saw increases among younger adults only in the incidence of gastric noncardiac cancer – which showed a 2.16% annual increase in incidence among those aged 30-34 years – and leukemia, where there was a 1.33% annual increase in incidence in the same age group.

But the incidence of eight cancers, including those related to smoking and infection, decreased each year among younger adults.

“Our findings expose a recent change that could serve as a warning of an increased burden of obesity-related cancers to come in older adults,” study senior author Ahmedin Jemal, PhD, of the American Cancer Society, said in a statement. “Most cancers occur in older adults, which means that as the young people in our study age, the burden of obesity-related cancer cases and deaths are likely to increase even more. On the eve of World Cancer Day, it’s timely to consider what can be done to avert the impending rise.”

The future burden of these cancers could halt or even reverse the reductions in cancer mortality achieved over the past several decades, the investigators warned.

The study was funded by the American Cancer Society and the National Cancer Institute. No conflicts of interest were declared.

SOURCE: Sung H et al. Lancet Public Health. 2019 Feb 4 doi: 10.1016/ S2468-2667(18)30267-6.

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