Cancer Trends in Younger Adults: Insights from Recent Research

Cancer has traditionally been seen as a disease that affects older adults, but that is changing.

Today, our partners at the American Cancer Society published a comprehensive review of 20 years of cancer data, to show clearly that rates of certain cancers are increasing in younger adults. While pieces of this trend have been reported previously, today’s analysis from Hyuna Sung and colleagues, published in The Lancet Public Health, provides the fullest and most comprehensive picture to date. This important paper cements our certainty that these trends are real, illustrates the breadth of cancers included in this trend, and raises important questions about the future. With the incidence of cancer in the young on the rise, the overall costs of treating and managing cancer and its after effects are likely to get worse than they already are, further straining an already strained healthcare system.

Their results are startling and concerning.

What did they find?

The study revealed several critical trends:

50% of the cancers analyzed (17 of 34) show an increased incidence in younger people. 

The incidence of some cancers are more than 2x higher in young people compared to people born in 1955. In some cases, the trend seems to be getting worse over time, with progressively higher incidence rates in younger and younger cohorts. These cancers include small intestine cancer, kidney and renal pelvis cancer, pancreatic cancer, and liver cancers in females. This represents a dramatic increase.

The incidence of other cancers are also increasing, including some which had previously shown a downward trend. These include estrogen-receptor-positive breast cancer, uterine corpus cancer, colorectal cancer, non-cardia gastric cancer, gallbladder, ovarian, testicular cancer, anal cancer in males, and Kaposi sarcoma in males. 

A few cancers show increased mortality rates as well. 

These include liver cancer, uterine corpus cancer, gallbladder cancer, testicular cancer, and colorectal cancers. However, for most cancer types, mortality rate ratios (MRRs), a measure of the mortality rate of a given cancer, either declined or stabilized in younger cohorts.

What factors are causing the increase?

It’s not completely clear, but there are hints.

The authors make a strong case that these trends are related to exposures to risk factors that are experienced similarly by people born around the same time, at the same time in their lives. Their careful statistical analysis was designed to control for things that would impact all ages similarly, for example improvements in detection or treatment. Interestingly, a few of the most positive findings in the paper make the case most strongly that environmental factors are largely at play– cases where we see, thankfully, a reduction in cancer incidence in younger people.

10 of the 17 cancers that are increasing in incidence are known to be obesity-related, including colorectal cancer, uterine corpus cancer, gallbladder and other biliary cancer, kidney and renal pelvis cancer, and pancreatic cancer. Some of these associations have been previously established, but the scale and scope of the impact is striking to see. We know that obesity has been on the rise in the US since the 1970s across all age groups, but has been most severe among younger people. We also know that the influence of bodyweight during early adulthood can increase the risk of cancer generally as well as other cardiometabolic conditions. 

The authors summarize other emerging theories that might explain these trends. Sedentary lifestyles during adolescence and young adulthood have been associated with an increased risk for colorectal and breast cancers. Some people suggest that changes in dietary patterns and antibiotic use lead to an altered microbiome, which could lead to increased risk of certain gastrointestinal cancers. Additionally, a reduction in oral contraceptive use from 1970s – 1990s may have contributed to the increase in ovarian cancer risk. 

What is clear is that understanding these trends is crucial for shaping effective public health strategies. If the risk factors are environmental, it suggests that they are modifiable. Future research should explore early-life exposures and their long-term impact on cancer risk. Longitudinal studies are needed to understand the role of environmental and genetic factors in these trends.

What does this mean for healthcare?

This paper demonstrates that cancer is not a problem we can wish away, or will be rid of soon. We will all be living with the impacts of these trends for decades to come. In the simplest terms, it means that we can anticipate more, and younger, cancer patients. As, for the most part, mortality rates have remained stable or continued to decline, it means that we can also anticipate more cancer survivors, for longer. Finding these people, and supporting them on that road through screening, diagnosis, treatment, and recovery, will become even more important. 

Early detection matters more than ever. We know the cost of treating cancer increases and the likelihood of surviving cancer decreases if the cancer is caught too late. We also know that cancer screening just isn’t on the radar for many young people or on the mind of their doctors. Mechanisms to simplify the process of developing and deploying screening protocols across younger, working age people, and effective protocols for following up on abnormal findings in a fast and cost-effective way, can have an outsize impact on minimizing the cost of these trends and on saving lives. 

Finally, all of us– from healthcare systems, to employers, to families– will have to adapt to address the unique needs of younger cancer patients, who may face different challenges compared to older patients. This includes addressing issues related to fertility, long-term survivorship, and psychosocial support.

The importance of this study by Hyuna Sung and the American Cancer Society cannot be overstated. We can learn to manage what we can see, and if we can better predict the future cancer burden we can better mitigate it, ultimately improving public health outcomes. This paper helps us direct our energy and intelligence towards driving outcomes that can buy decades of productive life.