Cancer Incidence Is Rising Among Millennials

Cancer Incidence Is Rising in Generations X and Y in the United States

Research led by Dr. Hyuna Sung of the American Cancer Society found rising cancer incidence among Generations Y and X in the United States. It was published in The Lancet Public Health. Researchers identified increases in 17 cancers: 8 that rose in each successive birth cohort and 9 that had declined in earlier generations.

Dr. Sung said, "These findings expand the evidence of increasing cancer risk in generations born after World War 2, extending previous findings on early-onset colorectal cancer and several obesity-related cancers to a broader range of cancer types." Although researchers could not clearly explain why cancer rates are rising, they identified trends associated with birth years.

Dr. Sung's team analyzed data on cancer patients aged 25-84, evaluating records for 23.6 million patients and 7.3 million cancer deaths. Patients were divided into five-year birth cohorts.

Cancer incidence rates increased across successive birth cohorts for 11 cancers.

Cancer incidence means the number of newly diagnosed cases in a particular population over a specified period. It is generally calculated as new cases per 100000 people and is an important indicator of cancer frequency and distribution.

Which Cancers?

These included myeloma, leukemia, small intestine, thyroid, kidney and renal collecting system, pancreatic, soft tissue and gastric cancers. Among women, increases were found in liver and intrahepatic bile duct cancers, esophageal adenocarcinoma, and non-HPV-related oral cavity and pharyngeal cancers.

Compared with patients born in 1955, those born in 1990 had:

• A 3.56-fold increase in small intestine cancer incidence,
• 3.29-fold higher thyroid cancer incidence,
• 2.92-fold higher kidney and renal collecting system cancer incidence, and
• 2.61-fold higher pancreatic cancer incidence, with cancer rates overall 2 to 3 times higher.

Compared with women born in 1955, women born in 1990 had 2.05-fold higher incidence of liver and intrahepatic bile duct cancer, while women born in 1985 had 1.26-fold higher incidence of non-HPV-related oral cavity or pharyngeal cancer.

The researchers reported a significant birth-cohort effect on incidence trends for 8 of the 11 cancers (Pcohort <.05), but not for thyroid cancer, soft tissue cancer or female esophageal adenocarcinoma.

Mortality Rates

Mortality data were available for 8 of the 11 cancers. Myeloma and leukemia mortality rates were lower in the 1990 cohort than in the 1955 cohort. Small intestine, thyroid and soft tissue cancer mortality remained stable across cohorts, while pancreatic and kidney/renal collecting system cancer mortality fluctuated.

For liver and intrahepatic bile duct cancer in women, mortality increased in later birth cohorts. Compared with the 1955 cohort, women in the 1980 cohort had a 1.36-fold higher mortality rate for these cancers.

• The fastest annual incidence increases in young adults (ages 25-49):

  • Pancreatic cancer: 4.34 percent; ages 25-29.
  • Small intestine cancer: 4.22 percent; ages 25-29.
  • Kidney and renal pelvis cancer: 3.93 percent; ages 35-39.

• For most cancers, mortality rates in young adults:

  • Generally declined or remained stable.
  • However: Mortality from liver and intrahepatic bile duct cancer in women increased by 1.95 percent annually (Page <.05).

Commentary

Rising cancer rates in younger generations reveal differences in risk across generations and are considered an early indicator of the future cancer burden. If this elevated risk persists without effective population-level interventions, decades of progress against cancer could stall or reverse. The research points to a critical need to identify underlying risk factors in Generations X and Y and develop prevention strategies.