Study details

For the study, researchers from the American Cancer Society (ACS) looked at 34 of the most common cancers using data from more than 23 million patients diagnosed with cancer between Jan. 1, 2000, and Dec. 31, 2019. The researchers also looked at mortality data from more than 7 million deaths for 25 types of cancers during the same period.

Researchers then calculated incidence rate ratios for each birth cohort, adjusted for "age effect and period effect."

The researchers found that cancer incidence rates continued to rise in each generation in 17 of the cancers, including breast, pancreatic, and gastric cancers. For eight of those 17 cancers, the study found that cancer incidence rates increased for each successive birth cohort since 1920, and for nine of the cancers, incidence rates increased in younger cohorts after declining in older cohorts.

The youngest birth cohort, 1990, saw a cancer incidence rate range from 12% higher than the birth cohort with the lowest rate for ovarian cancer, to 169% higher than the birth cohort with the lowest rate for uterine corpus cancer.

The cancer incidence rate for the 1990 birth cohort was also two-to-three times higher for pancreatic, kidney, and small intestinal cancers than the 1955 birth cohort.

Researchers also found that for five cancers — liver and endometrial in females, testicular in males, and colorectal and gallbladder cancers in all genders — young adults were more likely to die than prior generations.

However, the study also found that that cervical cancer decreased significantly among millennials and Gen X, especially in millennial women, which the researchers said could be linked to the effectiveness of the HPV vaccine.

Discussion

According to Hyuna Sung, lead author of the study, the 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."

"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 critical development years," Sung added.

Ahmedin Jemal, a senior author on the study, said the findings highlight the need to identify and address the "underlying risk factors in Gen X and Millennial populations" to explain and address rising cancer rates.

"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," Jemal said. "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."

William Dahut, chief scientific officer for ACS, said it's especially concerning that young adults are more likely to die of five types of cancer than previous generations, because it's "despite the fact that we have much better drugs for a lot of them."

"It's really sort of scary to see all in one dataset," said Andrea Cercek, co-director of the Center for Young Onset Colorectal and Gastrointestinal Cancers at Memorial Sloan Kettering Cancer Center.

"But it definitely reflects what we've known and what we've noticed as well in our clinics," she added. "We really have no idea why." (Fortinsky, The Hill, 7/31; Johnson, Forbes, 7/31; Reed, Axios, 7/31)

Advisory Board's oncology resources

For more insights on oncology, check out these Advisory Board resources:

Growth in demand and costs, as well as innovative technologies and disruptors, will change how cancer care is delivered, experienced, and paid for going forward. This resource outlines four predictions for how the cancer care delivery landscape will evolve by 2030.

Separately, this expert insight explains three strategies organizations can use to leverage oncology pharmacists and improve cancer care. Similarly, these ready-to-use slides outline the major structural shifts impacting cancer care and the strategic decisions that oncology leaders will need to make.