A significant new study led by researchers at the American Cancer Society (ACS) has revealed a troubling trend: incidence rates are continuing to rise among younger generations for 17 of the 34 cancer types examined, including breast, pancreatic, and gastric cancers. Additionally, mortality trends have increased in line with incidence rates for liver (female only), uterine corpus, gallbladder, testicular, and colorectal cancers. These findings will be published today in the journal The Lancet Public Health.
Expanding Cancer Risk Among Post-Baby Boomer Generations
“These findings add to growing evidence of increased cancer risk in post-Baby Boomer generations,” said Dr. Hyuna Sung, the lead author of the study and a senior principal scientist of surveillance and health equity science at the American Cancer Society. The study builds upon earlier research into early-onset colorectal cancer and obesity-related cancers, broadening the scope to include a wider range of cancer types. Dr. Sung explained that birth cohorts, or groups of people categorized by their birth year, share unique social, economic, political, and environmental factors that influence their exposure to cancer risks during their crucial developmental years. However, despite identifying cancer trends associated with specific birth years, the reasons behind these rising rates remain unclear.
Detailed Analysis and Findings
In their analysis, researchers gathered incidence data from 23,654,000 patients diagnosed with 34 types of cancer and mortality data from 7,348,137 deaths across 25 types of cancer. The study focused on individuals aged 25-84 years between January 1, 2000, and December 31, 2019. Data were sourced from the North American Association of Central Cancer Registries and the U.S. National Center for Health Statistics. To compare cancer rates across generations, the researchers calculated birth cohort-specific incidence and mortality rate ratios, adjusting for age and period effects, and separated the data by five-year birth intervals from 1920 to 1990.
The study found that incidence rates increased with each successive birth cohort since approximately 1920 for eight of the 34 cancers studied. Notably, the incidence rate for pancreatic, kidney, and small intestinal cancers was approximately two to three times higher in the 1990 birth cohort compared to the 1955 birth cohort for both males and females. Similarly, liver cancer incidence rates were higher for females in the younger cohorts. The study also observed a rise in incidence rates among younger cohorts for nine additional cancers, following a decline in older birth cohorts. These cancers included breast cancer (estrogen-receptor positive only), uterine corpus cancer, colorectal cancer, non-cardia gastric cancer, gallbladder cancer, ovarian cancer, testicular cancer, anal cancer in males, and Kaposi sarcoma in males. The incidence rate in the 1990 birth cohort ranged from 12% higher for ovarian cancer to 169% higher for uterine corpus cancer compared to the cohort with the lowest incidence rate. Furthermore, mortality rates increased in younger birth cohorts for liver cancer (female only), uterine corpus, gallbladder, testicular, and colorectal cancers, mirroring the rising incidence rates.
Implications and Future Concerns
“The increase in cancer rates among this younger group of people indicates generational shifts in cancer risk and often serves as an early indicator of future cancer burden in the country,” commented Dr. Ahmedin Jemal, senior vice president of surveillance and health equity science at the American Cancer Society and senior author of the study. Without effective population-level interventions, the elevated risk in younger generations could lead to an overall increase in cancer burden as these individuals age, potentially halting or reversing decades of progress against the disease. Dr. Jemal emphasized the critical need to identify and address underlying risk factors in Generation X and Millennial populations to inform future prevention strategies.
Addressing the Growing Cancer Burden
“The increasing cancer burden among younger generations underscores the importance of ensuring people of all ages have access to affordable, comprehensive health insurance, a key factor in cancer outcomes,” said Lisa Lacasse, president of the American Cancer Society Cancer Action Network (ACS CAN). ACS CAN is committed to advocating for expanded Medicaid in states that have not yet done so, as well as pushing for the permanent extension of enhanced Affordable Care Act tax subsidies. These measures have been instrumental in providing access to care for millions and will continue to be a focus of ACS CAN’s efforts to combat the growing cancer crisis in younger generations.
