Summary: A study by the American Cancer Society shows rising cancer rates and mortality in younger generations for several types of cancer, including breast, pancreatic, and gastric cancers, indicating generational shifts in cancer risk.

Key Takeaways

  1. Rising Cancer Rates in Younger Generations: The ACS study shows that 17 out of 34 cancer types, including breast, pancreatic, and gastric cancers, have increasing incidence rates among younger generations.
  2. Increased Mortality Rates: Mortality rates have also risen for liver cancer (in females), uterine cancer, gallbladder cancer, testicular cancer, and colorectal cancer, highlighting a significant health concern for younger cohorts.
  3. Generational Risk Factors: The study suggests that unique social, economic, political, and climate environments experienced by different birth cohorts influence cancer risk factors, with newer generations facing higher risks for various cancers.

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An American Cancer Society (ACS) study published in The Lancet Public Health shows rising cancer rates in younger generations for 17 of 34 types, including breast, pancreatic, and gastric cancers. Mortality rates have also increased for liver (in females), uterine, gallbladder, testicular, and colorectal cancers. 

“These findings add to growing evidence of increased cancer risk in post-Baby Boomer generations, expanding on previous findings of early-onset colorectal cancer and a few obesity-associated cancers to encompass a broader range of cancer types,” says Hyuna Sung, PhD, lead author of the study and a senior principal scientist of surveillance and health equity science at the American Cancer Society. 

“Birth cohorts, groups of people classified by their birth year, share unique social, economic, political, and climate environments, which affect their exposure to cancer risk factors during their crucial developmental years,” Sung adds. “Although we have identified cancer trends associated with birth years, we don’t yet have a clear explanation for why these rates are rising.”

In this analysis, researchers obtained incidence data from 23,654,000 patients diagnosed with 34 types of cancer and mortality data from 7,348,137 deaths for 25 types of cancer for individuals aged 25-84 years for the period Jan 1, 2000, to Dec 31, 2019, from the North American Association of Central Cancer Registries and the U.S. National Center for Health Statistics, respectively. To compare cancer rates across generations, they calculated birth cohort-specific incidence rate ratios and mortality rate ratios, adjusted for age effect and period effect, by birth years, separated by five-year intervals, from 1920 to 1990.

Researchers found that incidence rates increased with each successive birth cohort born since approximately 1920 for eight of 34 cancers. In particular, the incidence rate was approximately two-to-three times higher in the 1990 birth cohort than in the 1955 birth cohort for pancreatic, Kidney, and small intestinal cancers in both male and female individuals; and for liver cancer in female individuals. 

Additionally, incidence rates increased in younger cohorts, after a decline in older birth cohorts, for nine of the remaining cancers including breast cancer (estrogen-receptor positive only), uterine corpus cancer, colorectal cancer, non-cardia gastric cancer, gallbladder cancer, ovarian cancer, testicular cancer, anal cancer in male individuals, and Kaposi sarcoma in male individuals. 

Need for Targeted Prevention in Younger Populations

Across cancer types, the incidence rate in the 1990 birth cohort ranged from 12% for ovarian cancer to 169% for uterine corpus cancer higher than the rate in the birth cohort with the lowest incidence rate. Notably, mortality rates increased in successively younger birth cohorts alongside incidence rates for liver cancer (female only), uterine corpus, gallbladder, testicular, and colorectal cancers.

“The increase in cancer rates among this younger group of people indicate generational shifts in cancer risk and often serve as an early indicator of future cancer burden in the country. Without effective population-level interventions, and as the elevated risk in younger generations is carried over as individuals age, an overall increase in cancer burden could occur in the future, halting or reversing decades of progress against the disease,” adds Ahmedin Jemal, PhD, senior vice president, surveillance and health equity science at the ACS and senior author of the study. 

“The data highlights the critical need to identify and address underlying risk factors in Gen X and Millennial populations to inform prevention strategies,” Jemal adds.