The next 20 years will see a big shift in cancer type rankings, researchers predict.
At the moment, the most common cancers in the United States are breast, lung, prostate, colorectal, and melanoma.
the study authors predicted. Breast cancer will remain the top cancer to be diagnosed, lung cancer will drop from second to third, and colorectal cancer will remain at fourth.
These predicted rankings of cancer types by their total number of annual cases were published online April 7, 2021, in JAMA Network Open.
The authors also rank cancer type by mortality. Currently, most cancer deaths are caused by lung cancer, followed by colorectal, pancreatic, and breast. By 2040, the most notable change in cancer deaths is that liver and intrahepatic bile duct cancer, currently at sixth, will jump up to third.
Two decades from now, the ranking in terms of cancer deaths will be lung, pancreatic, liver and intrahepatic bile duct, and colorectal.
“Our findings reflect the shifting dynamics of cancer screening and treatment,” lead author Lola Rahib, PhD, a pancreatic cancer scientist at Cancer Commons, the advocacy nonprofit, commented in a press statement.
The new analysis used population-growth projections (based on 2010 U.S. Census data) and current population-based cancer incidence and death rates (from Surveillance, Epidemiology, and End Results 2014-2016) to calculate the changes in incidences and deaths to the year 2040.
The projected, estimated numbers are not ironclad, the researchers acknowledged.
“Our projections assume that the observed rates and trends [from recent years] don’t change over time,” Dr. Rahib said in an interview, but she pointed out that change may indeed happen.
“Any long-term projections should be considered with a grain of salt,” said Kim Miller, MPH, a surveillance research scientist at the American Cancer Society, who was approached for comment.
Dr. Miller explained that “cancer trends can sometimes rapidly change within a few years.” Projections just 2-4 years ahead are “extremely difficult” and those 20 years ahead are even more so, she added in an interview.
“We’re encouraged to see the projected decreases in deaths from lung, colorectal, and breast cancer in the coming years,” said coauthor Lynn Matrisian, PhD, MBA, chief science officer at the Pancreatic Cancer Action Network. “It’s time to shift focus to some of the less commonly diagnosed cancers with the lowest survival rates, like pancreatic and liver cancer.”
Difference in opinion on prostate cancer
The huge fall in the incidence of prostate cancer that the authors predict will come about as a result of changes in prostate-specific antigen (PSA)–screening recommendations over the last 15 years, they suggested.
“The most recent change in 2018 recommends that men aged 55-69 can make their own decisions regarding screening, but previous changes recommended against PSA screening,” said Dr. Rahib.
“These changes in screening guidelines have influenced the number of diagnoses of prostate cancer in recent years and will continue to do so to 2040,” Dr. Rahib commented.
Dr. Miller casts doubt on this prediction.
Using data through 2017, “we have seen that the patterns in prostate cancer incidence are already shifting from the steep declines we saw in the early 2010s,” she said. “I would use caution when interpreting the overall trends for prostate, because this cancer in particular is dramatically affected by changes in recommendations for screening with the PSA test.”
Screening has also influenced colorectal cancer incidence, the authors pointed out, saying that the uptake of colorectal cancer screening is associated with a decrease in the number of colorectal cancers and deaths out to 2040, as a result of effectiveness of screening.
For breast cancer, the authors highlighted the fact that, although the number of breast cancers will continue to increase, the number of breast cancer deaths will decrease. That ongoing trend is most likely attributable to increased screening and advancements in treatment.
The study was supported by the National Institutes of Health, National Cancer Institute, the Cancer Prevention and Research Institute of Texas, Cancer Commons and the Pancreatic Cancer Action Network. The study authors and Dr. Miller disclosed no relevant financial relationships.
A version of this article first appeared on Medscape.com.