Cancer deaths are declining, but increase for some cancers in young adults, report says

Deaths from cancer have declined by 33% since 1991, averting 4.1 million deaths. However, more people are being diagnosed with cancer than ever before, and at an earlier age, according to a major new report from the American Cancer Society.

Experts say one big reason cancer deaths have declined is due to decreases in smoking rates, as well as improved treatments and targeted therapies. Still, experts are worried about the increase in some cancers in adults 50 and under - and say it's urgent to understand what's behind the troubling trend.

Especially concerning is the rising number of deaths of young people from colon cancer - the same illness that killed Marvel actor Chadwick Boseman at the age of 43.

Colon cancer is now the number one cause of death among men younger than 50, and the number two cause of death in women of the same age group. Colon and breast cancer now exceed lung cancer as leading causes of cancer death for those under the age of 50.

"It's something that wasn't represented in statistics yet - that there has been a creep toward younger age of onset of certain common cancers. Colorectal and breast are the dominant ones," said Dr. Larry Norton, oncologist and researcher at Memorial Sloan Kettering, and doctors and researchers have been noticing this in their practice and research.

For the first time, the projected number of new cancer diagnoses in the United States will top two million, which is equivalent to an alarming 5,480 diagnoses each day. Although the new data shows an overall continued decline in cancer death rates, the report reveals increased rates for 6 of the 10 most common cancers, including breast, prostate, uterine, pancreas, oral, liver, kidney and melanoma, as well as colorectal and cervical cancer in young adults.

Experts still aren't sure why certain cancer rates are increasing in younger adults, but say it could be due to rising rates of obesity, and still unknown environmental factors.

"I think we're all grappling with what is the broadly spoken environmental factor which is changing the cancer incidence and mortality amongst the young," said Dr. William Dahut, the chief scientific officer at the American Cancer Society.

Colon cancer and breast cancer top lung cancer as leading causes of death in those under 50

The nationwide report is consistent with prior smaller studies that have pointed to this trend.

In recent years, health officials have dropped the age for people with average risk to start screening from 50 to 45 for colon cancer, and 50 to 40 for breast cancer.

"Early diagnosis is really critically important for curing cancer. I like to find things earlier because it's not only an opportunity to cure people who otherwise might not be cured, but it's also an opportunity to cure them with less noxious therapy," said Norton.

For colon cancer, oncologists say that the trends in the U.S. are matched by other high-income countries and say it's possible the increase could be due to new lifestyles or environmental exposures for younger generations.

Environmental factors, such as exposure to chemicals in foods and in the air, and other currently unidentified factors, such as the recent legalization of cannabis and increased cannabis use, can't be ruled out as risk factors, said Norton.

"There are studies that even show that risk factors like whether or not you were breastfed, whether or not you had antibiotics at a high rate as a child -- that these factors might be predicting your chances of getting cancer when you're an adult," said Dr. Folasade May, gastroenterologist and researcher at UCLA Health.

Still, 30% of diagnoses for those under the age of 50 are related not to outside exposures, but rather to an underlying family history or genetic mutation, putting them more at risk, according to the American Cancer Society.

Whatever the reason, oncologists say people must get a colonoscopy when recommended, or earlier if they have symptoms such as blood in their stool, losing weight without trying, or a change in bowel habits that lasts more than a few days. There are also newer colon cancer screening tools that some patients may prefer, such as at-home stool testing.

"A lot of these younger folks that are dying from colorectal cancer, it's because they've had symptoms for a year or two before they finally talk to their doctor. And by the time they're getting into my clinic and getting a colonoscopy, that cancer is advanced to stage four. Survival for stage four is 13%," said May.

For breast cancer, the underlying reason for the higher death rates in younger Americans is likely due to a combination of factors. Researchers note that other trends such as a decrease in fertility and increasing obesity - are both risk factors for breast cancer.

Uterine cancer is the only cancer where survival has decreased, likely due to racial disparities

According to the new report, uterine cancer was the only cancer for which death rates across all age groups have been increasing over the past 40 years.

"There are a number of troubling statistics about this cancer," said Dr. Ursula Matulonis, chief of the division of gynecologic oncology at the Dana-Farber Cancer Institute and Professor of Medicine at Harvard Medical School.

Compared to white Americans, the risk of dying of uterine cancer is 33% higher in Black people, and 51% higher in American Indians and Alaska Natives. This is primarily due to growing racial disparities.

Specifically, Black women are less likely to get a timely diagnosis - which dramatically decreases the chance they will survive their cancer. According to the report, 56% of Black women were diagnosed in earlier stages, versus 72% of white women. Black women were half as likely to receive diagnostic procedures that were in line with current medical guidelines.

According to oncologists, primary care doctors and the general public should understand these stark racial disparities for uterine cancer, so patients and doctors alike can advocate for potentially life-saving cancer screenings.

"I think we're poised to develop new treatment paradigms, that I'm confident will impact how patients are treated - from a prevention standpoint, early detection standpoint. There's not an early detection test for uterine cancer," said Matulonis.

"Equity research and equity outreach is a very, very important part of our entire approach towards screening for cancer," said Norton.

Aishwarya Thakur, MD, is a resident physician in pediatrics at Columbia University/NewYork-Presbyterian Hospital and a member of the ABC News Medical Unit.