Worldwide, cancer diagnoses are growing more common among people under 50, and it’s been estimated that by 2030, the number of these early-onset cancer diagnoses could increase by roughly 30% – and the number of those who die from their conditions could rise by about 20%.

And researchers in the US have found that around 134 000 cancer diagnoses were missed in during the Covid-19 pandemic.

The most striking finding in the past decade, however, has been the increase in cases among young adults, according to Ahmedin Jemal, senior vice-president of surveillance and health equity science at the American Cancer Society (ACS).

Cancer is still most commonly diagnosed among people older than 65, and in the US, only about 12% of cancers are diagnosed among people under 50, according to ACS data.

American women have about a one in 17 chance of being diagnosed before turning 50, while men have about a one in 29 chance, the ACS says. (Women are more likely to be diagnosed largely because breast cancer is so common.)

But those odds are gradually getting worse. In 2019, about 103 cancers were diagnosed among every 100 000 US adults younger than 50, up from about 100 in 2010, according to more recent findings.

TIME reports that this may seem like a small overall increase, but it’s not a good sign, especially because during the same period, incidence rates among older US adults decreased.

For certain cancers, the numbers are especially striking. Colorectal cancer is now diagnosed among young adults almost twice as often as it was in the 1990s, while other types of gastrointestinal cancer are also on the rise among this population.

Early-onset breast cancer is becoming more common too, with its incidence rising by almost 4% among US women every year from 2016 to 2019, according to a 2024 study.

Even lung cancer, a disease typically associated with older cigarette smokers, is now, to a surprising degree, affecting younger women, even those who have never smoked, said Dr Matthew Triplette, a pulmonologist at Fred Hutch Cancer Centre in Seattle.

What’s driving these trends?

Triplette said he doubts there’s “some new, very dangerous cancer risk factor out there that’s causing tons of excessive cases in younger folks”.

Cancer is a complex disease influenced by a mixture of genetics, lifestyle choices, and environmental exposures, so it’s unlikely there’s a single explanation for the data.

Instead, it’s probably a mix of things. Eating lots of processed foods, not enough exercise, and drinking too much alcohol are all risk factors, and all of those issues are widespread in modern life.

A 2019 study co-authored by Jemal found that many of the cancers growing more common among US young adults are linked to obesity, which now affects about 40% of under-40 IS adults.

Even big societal changes could have an impact. For example, women who give birth to their first child at 35 or younger tend to have a lower risk of breast cancer.

Missed during Covid

Meanwhile, the University of Kentucky Markey Cancer Centre study – published in JAMA Oncology – has provided the first estimates of missed cancer diagnoses in 2020, using nationwide surveillance data.

Although researchers expected detection rates to have been affected because of delayed screenings and missed healthcare appointments during the pandemic, until now, the extent of this impact had not been quantified. These new findings foreshadow even greater consequences reports News-Medical.Net.

“The longer cancer exists undetected, the lower the chances of positive patient outcomes. Every missed detection is a lost opportunity to beat the disease at its most treatable stage,” said Krystle Lang Kuhs, the paper’s senior author, co-leader of the UK Markey Cancer Centre’s Cancer Prevention and Control Research Programme and associate professor at the UK College of Public Health.

The report’s findings are expected to help inform where the US healthcare system can make up ground in cancer screening and detection and give insight into how similar disruptions could affect cancer diagnoses in the future.

The research also underscores the importance of timely dissemination of data, said Todd Burus, lead author and part of Markey Cancer Centre’s Community Impact Office.

“It is unfortunate that we are only able to perform this assessment more than two years after the fact,” he added. “We must invest the resources necessary to have more timely tracking of trends in cancer incidence so that we can target responses to the places they’re needed sooner.”

The study relied on data from the US Cancer Statistics Public Use Database June 2023 release, the first release available with 2020 cancer incidence data for all 50 states.

Using trends from previous years, the team calculated the expected cancer rates for March to December 2020 and compared this with what was actually reported.

Results showed that overall cancer diagnoses were 13% lower than expected during those 10 months, including a 28.6% reduction from expected during the period of widespread lockdown orders in March to May 2020.

The researchers also examined incidence rates by cancer type and stage of diagnosis, and among different populations.

Key findings include:

Prostate, female breast, and lung cancers had the largest numbers of potentially missed cases during the 10-month period at 22 950 cases, 16 870 cases and 16 333 cases, respectively.

Cancers with recommended, high-evidence screenings (female breast, cervical, colorectal and lung) saw a total rate reduction of 13.9% versus expected. Rates of female breast cancer showed signs of recovery to previous trends after the first three months of the pandemic, but levels remained suppressed for cervical, colorectal and lung cancers throughout the 10-month period.

Significant reductions occurred among both early and late-stage diagnoses of most cancer sites examined.

States that implemented lockdown orders in excess of six weeks saw a greater disruption to cancer diagnoses than those with less restrictive measures, particularly among lung, kidney and pancreatic cancers.

The paper’s authors also stress the need to continue following this data in the coming years to understand how undetected cases from 2020 will affect future trends in cancer mortality and survival.