1. Nolen, Lindsey

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As increased research studies yield great medical insights, formal health recommendations are often in need of adjustments. Since the last publication update in 2017, the United States Multi-Society Task Force (MSTF) on Colorectal Cancer (CRC) has made amendments to the CRC screening recommendations. These updates focus on specific questions regarding when to start and when to stop CRC screening in average-risk individuals. This includes individuals without family history of colorectal neoplasia and those without gastrointestinal symptoms.

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"The task force felt that there was an accumulation of new evidence from 2017 on these specific questions that required systematic review to determine if our 2017 recommendations, or the strength to support them, may change," said Swati Patel, MD, lead author and Director of the Gastrointestinal Cancer Risk and Prevention Center at the University of Colorado Anschutz Medical Center. "After thorough evidence review, we determined that there was sufficient evidence to change the recommendation about when to start colorectal cancer screening; however, the recommendation on when to stop screening remains unchanged."


Representing the American College of Gastroenterology, the American Gastroenterological Association, and the American Society for Gastrointestinal Endoscopy, the MSTF now suggests that CRC screening be conducted in average-risk individuals ages 45-49 years old. According to the task force, these updated recommendations were based upon evidence demonstrating an increasing incidence and mortality from CRC in individuals under age 50.


Further, data suggests that the yield of screening in 45-49 year-olds is similar to the yield of screening in 50-59 year-olds. The task force adds that benefits of screening in younger individuals outweighs the harm and cost based on modeling studies. According to Patel, the main reasoning behind expanding screening to 45-49 year-olds included the following:


* the increasing disease burden in this age group;


* evidence showing that the yield of screening in this age group is similar to the yield of screening in those who are already eligible for screening (50-59 year-olds, African Americans age 45 and older); and


* modeling studies that show that benefits outweigh risks and costs.



"Starting screening at age 45 will save lives. When you look at the increasing rates of colorectal cancer and how frequently it's being diagnosed in the U.S., there's this jump in cases between 49 and 50. That's not because there is something biologically different between 49- and 50-year-olds; it's because when patients are eligible for screening, there is a spike in diagnoses in people who had probably had colorectal cancer for several years and didn't have symptoms," Patel explained.


"That really suggests to us that, if we had the option to offer screening at age 45, that those patients could be diagnosed at earlier stages or the cancer could potentially even be prevented altogether."


These updates resulted from the Surveillance, Epidemiology, and End Results (SEER) Program, which provides information on cancer statistics in an effort to reduce the cancer burden among the U.S. population. SEER is supported by the Surveillance Research Program in National Cancer Institute's Division of Cancer Control and Population Sciences. Ultimately, data from SEER has shown a steady increase in the incidence of colorectal cancer in those under the age of 50 in the U.S. This same database has also shown an increase in death from colorectal cancer in this age group.


"We don't have a full understanding of why the incidence and mortality associated with CRC diagnosed in individuals under age 50 (early-age onset CRC, or EAO-CRC) is increasing over the last several decades. Previous work has suggested what is called a 'birth cohort effect.' This means that there are likely shared generational risk factors early in life that increase cancer risk over a lifetime and that individuals carry this risk with them as they age," Patel noted.


She added that researchers observe this "birth cohort effect" in colorectal cancer, with those born after the 1960s carrying a higher risk of developing cancer at younger ages than prior generations. The incidence of EAO-CRC has also been observed in other Westernized countries, suggesting that there are possible risk factors associated with Westernization that may be contributing to risk. Possibilities include sedentary lifestyles, early changes in the gut microbiome (from childhood antibiotics, antibiotics in the food chain, or increase in C-section deliveries), or even possibly ambient/water exposures that researchers are unaware of.


"There is a lot of research that needs to be done (and is underway) to fully understand the risk factors and causes of EAO-CRC. We are not surprised to learn that advanced colorectal neoplasia rates in 45-49 year-olds is similar to that observed in 50-59 year-olds.


"This is likely because of a combination of the 'birth cohort effect' where younger generations are carrying increased risk with them. Advanced polyps take a long time to grow and there are likely many asymptomatic cancers and advanced polyps among those age 45-49 that are not diagnosed until an individual gets a screening test," Patel noted in an interview with the ACP Internist, a publication of the American College of Physicians.


While the suggested minimum screening age has been decreased by 5 years, the MSTF still strongly recommends CRC screening in all individuals aged 50-75 who have not already initiated screening-as per the 2017 recommendations update. Other unchanged recommendations note that individuals aged 76-85 should decide to start or continue screening, which should be individualized and based on prior screening history, comorbidity, life expectancy, CRC risk, and personal preference. Screening is not recommended after age 85.


Prior to 2017, the last update to MSTF screening guidelines took place in 2008. The MSTF does not have a set schedule at which time recommendations are updated, but rather issues updates when sufficient evidence has accumulated such that either a recommendation or the strength that supports a recommendation may change. These are designed to be practical guides for clinicians.


Updated guidance from the MSTF is aligned with multiple other professional societies, including the United States Preventive Services Task Force, the National Comprehensive Cancer Network, and the American Cancer Society. The MSTF provides consensus recommendations that are reviewed/approved by all three societies using the Grading of Recommendations Assessment, Development and Evaluation (GRADE) process.


This process separates the quality of evidence available from the strength of the recommendation, allowing the task force to incorporate other factors that influence a recommendation, such as preferences, values, and cost. Moving forward, Patel also explained that there are multiple areas of active research in this field, including understanding risk factors for cancer in young patients and determining whether we can personalize screening and if there should be a preferred screening modality in younger patients. Researchers are also studying and implementing ways to ensure equitable access to screening, and exploring other prevention strategies such as diet, lifestyle, medications.


"Colorectal cancer is unique in that we not only have tests that can screen for cancer and detect it at early stages, but we also have tests that can prevent it altogether by removing precancerous colorectal polyps," said Patel. "Our goal in pinpointing starting and stopping ages was to optimize the population of patients in our society who would benefit most from the early detection and prevention."


The task force will continually assess accumulating evidence and revise recommendations accordingly. Like many of the other organizations providing guidance in this space, the MSTF does not have a set schedule at which time recommendations are updated. Rather, the task force initiates an update when there is a consensus among members that there may be enough new evidence such that a recommendation might change or the strength that supports a recommendation might change. Based on this consensus, a systematic literature review is conducted and then recommendations are formulated based on this review. Sometimes this results in updates (for instance the age to start screening), and other times this reinforces prior recommendations (such as the age to stop).


Lindsey Nolen is a contributing writer.


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