Researchers identify possible contributors to global surge in early-onset cancers
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A dramatic rise in global incidence of early-onset cancers over the past 30 years may be related in part to increased exposure to risk factors at a young age, according to study results published in Nature Reviews Clinical Oncology.
For the study, researchers at Brigham and Women’s Hospital and Harvard T.H. Chan School of Public Health analyzed available data, including information on early life exposures, to better understand the increase in cancer diagnoses among individuals aged younger than 50 years.
The researchers identified a so-called “birth cohort effect,” demonstrating that each consecutive group of people born at a later time had a higher risk for cancer onset later in life, likely related to exposure to risk factors at a young age.
“There is a temporal increase in the prevalence of putative risk factors for early-onset cancer, such as obesity, smoking or physical inactivity,” lead researcher Tomotaka Ugai, MD, PhD, research scientist at the department of pathology's molecular pathological epidemiology program at Brigham and Women’s Hospital, told Healio. “The prevalence of these factors has increased over the past few decades. In addition, we speculate that there is a critical or sensitive time period when these factors are crucial for development of early-onset cancers.”
Ugai spoke with Healio about the study’s findings, their likely implications and what can be done to halt this pattern.
Healio: What prompted you to conduct this study?
Ugai: We got the invitation to write the Nature Reviews Clinical Oncology article about early-onset colorectal cancer — a very hot topic not only for research, but also for public health. Incidence of early-onset colorectal cancer has increased over the past few decades. After the invitation, we published an article about early-onset colorectal cancer 2 years ago in Nature Reviews Clinical Oncology. However, at that time, we found that the incidence of early-onset cancer has increased for many other types of cancer over the past few decades. No prior research has comprehensively analyzed the global incidence of early-onset cancer. That was our first motivation for this study.
Healio: How did you conduct this study?
Ugai: This study can be divided into four parts. In the first part, we analyzed the global incidence of early-onset cancer using an international, public database of global cancer incidence and mortality. In the second part, we summarized current evidence on the temporal trends of possible risk factors for early-onset cancers. In the third part, we also summarized evidence on risk factors and tumor characteristics of early-onset cancers by each cancer type. In the last part, we discussed research gaps and strategies to address those gaps.
Healio: What did you find?
Ugai: We comprehensively analyzed global incidence of early-onset cancer in 44 countries between 2000 and 2012. Our findings revealed that early-onset cancer has increased in many cancer types over the duration of the study. That’s a very new finding. We also found that, based on the previous literature and the current evidence, cancer risk factors have dramatically changed over the past few decades — or even as early as 1950 or 1960.
Healio: Why do you think early-onset cancer incidence has increased with each group of people born in later decades?
Ugai: We found that an individual’s early life “exposome,” which includes diet, weight, environmental exposures and microbiome, has changed a great deal in recent decades. The prevalence of obesity, smoking, inactivity, sleep deprivation, alcohol consumption and a Westernized diet have changed over the past few decades. We found that although the duration of sleep has not changed much in adults over the past decades, children’s sleep duration has decreased substantially. We also found significant increases in highly processed foods, sugary beverages, type 2 diabetes, inactivity and alcohol consumption since the 1950s.
Of the 14 cancer types we evaluated, eight were related to the digestive system. Diet has a direct impact on the microbiome, and changes in diet over time can influence disease risk. This link of diet to the microbiome may be contributing to an early-onset cancer epidemic.
Healio: What should be done to correct this?
Ugai: More research is needed to illustrate the reasons these changes are happening. Currently, what we can do is to avoid established risk factors, such as Western-style diets — highly processed foods, animal fats and sugar. In addition, exercising regularly, avoiding smoking and drinking, getting enough sleep and having a regular sleep schedule are important. We also like to highlight the importance of early life exposures. So, children should avoid these lifestyle and environmental factors as early in life as possible.
Healio: Should clinicians be speaking to parents about this?
Ugai: Yes, of course. It is very important to communicate with parents about the need to minimize a child’s early life exposures to these risk factors. It is also important to speak with younger adults about the importance of preventive measures. Communicating this message has become very important — we need to understand and stop this trend. Our children and future generations are depending on us.
For more information :
Tomotaka Ugai, MD, PhD, can be reached at Brigham and Women’s Hospital and Harvard T.H. Chan School of Public Health, 221 Longwood Ave., EBRC Room 415, Boston, MA 02215; email: tugai@bwh.harvard.edu.
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