New Study Reveals Millennials and Gen Xers Face Elevated Risk of 17 Cancers Compared to Previous Generations

Experts have been trying to learn about cancer for years, and a new study may give us valuable insight into the risks associated with the disease (National Cancer Institute/Unsplash)

A new groundbreaking study conducted by researchers from the American Cancer Society (ACS) and the University of Calgary in Canada revealed that Millennials and Gen Xers have a greater risk of 17 different kinds of cancers compared to previous generations.

What is Cancer?

Cancer is a genetic disease. This means changes in genes, which control the way our cells function, cause this disease. When one gets cancer, some of the body’s cells start to grow uncontrollably and eventually spread to other parts of the body.

Some genetic changes that can cause cancer are mistakes in cell division, damage to DNA caused by substances in the environment, like the chemicals in tobacco smoke and ultraviolet rays from the sun, or simply inheriting it from one's parents

Usually, the body eliminates the cells with damaged DNA before they get the chance to become cancerous, but the body’s ability to eliminate these cells decreases with age. Hence, this usually increases the risk of cancer later in life.

Cancer can begin anywhere in the body. The human body is made up of trillions of cells; it is normal for cells to grow and multiply (a process called mitosis) as new cells are needed due to cells growing old, becoming damaged, or dying. However, if this orderly process encounters any complications, cells could grow and multiply when they shouldn’t. Lumps of tissue (made up of extra cells), known as tumors, can form. Tumors can either be cancerous (also known as malignant) or noncancerous (also known as benign). If a tumor is cancerous, the cancerous cells can spread throughout the body to form new tumors in distant places (a process known as metastasis). If the tumor is benign, however, then the tumor will not spread or invade other tissues. Nevertheless, these tumors could become life-threatening if grown too large.

How Prevalent is Cancer?

In 2022, there were an estimated 20 million new cancer cases and 9.7 million deaths. About one in five people develop cancer in their lifetime, of which approximately one in nine men and one in 12 women die from the disease. It is estimated that by 2050, the number of cancer cases will increase to 35 million based solely on projected population growth.

Study Findings

First published in The Lancet this month, a new study found that 17 out of 34 common cancers were more prevalent in Gen Xers and Millennials in the United States.

These 17 cancers are:

Colon and rectal cancer
Gastric cardia cancer
Small intestine cancer
Kaposi sarcoma in men
Liver and intrahepatic bile duct cancer in women
Estrogen receptor-positive breast cancer in women
Ovary cancer in women
Non-HPV-associated oral and pharynx cancers in women
Anus cancer
Uterine corpus cancer in women
Testicular Cancer in men
Gallbladder and other biliary cancer
Kidney and renal pelvis cancer
Pancreatic cancer
Myeloma cancer
Non-cardia gastric cancer
Leukemia

Researchers from the ACS and the University of Calgary in Canada examined approximately 24 million patients diagnosed with 34 types of cancer and about seven million deaths from 25 cancers during the period from January 1, 2000, to December 31, 2019. After obtaining this information, researchers organized the data into birth cohorts to get a clearer picture of the data. To create said birth cohorts, researchers calculated cancer incidence rates and cancer death rates by birth years, separated by five-year intervals, from 1920 to 1990. For example, people born between 1920 and 1924 were all in one birth cohort, while people born in 1925 and 1929 were in a separate birth cohort. This pattern followed all the way through 1990.

While analyzing the data in birth cohorts, researchers found that the prevalence rates increased with each successive cohort born since about 1920 for eight of the 34 cancers. The rate was between two to three times higher for those born in 1990 than for those born in 1955 for pancreatic, kidney, and small intestinal cancers in both men and women and for liver cancer in women. Changes in rates ranged from 12% higher for ovarian cancer to 169% higher for uterine corpus cancer when compared with the birth cohorts that had the lowest prevalence rates.

Dr. Andrea Cercek, a gastrointestinal medical oncologist at the Memorial Sloan Kettering Cancer Center who was not involved with the research said, “The most important thing it tells us is there is something that changed for the group of individuals born after this period of time. They have been exposed to some environmental or lifestyle factor that is leading to this shift.”

Researchers found that 10 of the 17 cancers with increased prevalence were associated with obesity. These cancers are as follows:

Kidney and renal pelvis cancer
Estrogen receptor-positive breast cancer
Colon and rectal cancer
Gallbladder and other biliary cancers
Uterine corpus cancers
Myeloma
Pancreatic cancer
Cardia gastric cancer
Ovary cancer
Liver and bile duct cancer

“All of these cancers are linked to the obesity epidemic. We know that’s the second-leading cause of cancer right now, behind tobacco use,” said Dr. Otis Brawley, Professor of Oncology and Epidemiology at Johns Hopkins University.

The prevalence of obesity marginally during the 1960s and 1970s. However, it increased sharply over the next decades. Obesity prevalence went from 13.4 percent in 1980 to 34.3 percent in 2008 among adults. Additionally, the rate increased from five percent to 17 percent among children during the same period. At least 18 percent of all cancers and about 16 percent of cancer deaths in the US are related to excess body weight, physical inactivity, alcohol consumption, and/or poor nutrition. Many of these cancers could potentially be prevented by following physical and nutritional recommendations from ACS.

Though the study found that mortality declined or was stable in younger generations for most cancers, the mortality rate for several cancers increased among the younger generations. These cancers include:

Colorectal and testicular cancers
Endometrial cancer
Liver cancer among women
Intrahepatic bile duct cancer
Gallbladder cancer

“That was a sobering finding,” said Hyuna Sung, a cancer epidemiologist at the American Cancer Society, who led the research. “Although many cancer rates are rising, we don’t necessarily see this increase in mortality because we are treating them a lot better than before.”

As of today, nearly 42 percent of adults over 20 are obese, of which about nine percent are severely obese. This means that more than 100 million adults have obesity, and more than 22 million adults have severe obesity.

Researchers do not know the exact reason for the rise of certain types of cancers in younger generations, but obesity is a major suspect. However, Brawley said, “We can’t rule out other chemical exposures or chemical agents”.