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Does Getting Fit Guard Against Colorectal Cancer?
Evidence continues to mount that building cardiovascular fitness can help lower an individual's risk for colorectal cancer (CRC).
The latest study — a sweeping analysis of 643,583 individuals, with more than 8000 cases of CRC and 10 years follow-up — found a consistent, inverse, and graded association between cardiorespiratory fitness (CRF) and the risk for the development of CRC — a benefit similar for men and women and across races.
CRC risk was 9% lower for each 1-metabolic equivalent (MET) task increase in CRF, objectively measured by an exercise treadmill test.
When assessed across CRF categories, there was a progressive decline in CRC risk with higher CRF, Aamir Ali, MD, and colleagues with Veterans Affairs Medical Center, Washington, DC, found.
Compared with the least fit individuals (METs, 4.8), the CRC risk was 14% lower in those falling in the low-fit CRF category (METs, 7.3), 27% lower for moderately fit people (METs, 8.6), 41% lower for fit individuals (METs, 10.5), and 57% lower for high-fit individuals (METs, 13.6).
Moderate CRF is attainable by most middle-aged and older individuals, by engaging in moderate-intensity physical activity such as brisk walking, which aligns with current national guidelines, the authors said.
The study was published online on July 28 in Mayo Clinic Proceedings.
The results dovetail with earlier work.
For example, in the Cooper Center Longitudinal Study, men with high mid-life CRF had a 44% lower risk for CRC and a 32% lower risk of dying from cancer later in life men with low CRF.
A recent meta-analysis for the World Cancer Research Fund estimated a 16% lower risk for colon cancer in people with the highest levels of recreational physical activity relative to those with the lowest levels.
A recent UK Biobank analysis using accelerometers linked higher daily movement to a 26% reduction in risk across multiple cancers, including bowel cancer.
Taken together, the data suggest that 'the more you exercise, the better your overall health is going to be — not just your cardiac fitness but also your overall risk of cancer,' Joel Saltzman, MD, medical oncologist at Cleveland Clinic Taussig Cancer Center, Cleveland, noted in an interview with Medscape Medical News .
Can You Outrun CRC Risk?
In the US, CRC is the second leading cause of cancer mortality, accounting for 51,896 deaths in 2019. The economic burden of CRC in the US is significant, topping $24 billion annually.
And while the incidence of colon cancer has decreased in older individuals during the past 3 decades, the incidence in younger adults has nearly doubled during the same period, 'underscoring the limitations of screening programs and the critical need for risk factor modification,' Ali and colleagues wrote.
'There is good evidence that exercise and healthy lifestyle/diet have significant benefit overall and as well for some potential risk reduction for colon cancer,' David Johnson, MD, professor of medicine and chief of gastroenterology, Eastern Virginia Medical School in Norfolk, Virginia, told Medscape Medical News.
'There are clearly suggestions of why this makes sense via the beneficial effects of exercise and physical activity in CRC pathways including but not limited to regulation of inflammation and aberrant cell growth/cancer pathways,' Johnson said.
He emphasized, however, that exercise and lifestyle are not the best way to prevent CRC.
'Appropriate screening, in particular by colonoscopy (by skilled physicians who meet high-quality performance national benchmarks) to detect and remove precancerous polyps, is the best approach for prevention,' Johnson said.
'At this point — albeit exercise is potentially helpful and a great general recommendation — my most current advice as an expert in the field, is that you cannot outrun CRC risk,' Johnson said.
Can You Outrun CRC Recurrence?
Prevention aside, the data thus far are even more supportive of risk reduction for patients who have had CRC and are targeting reduction of recurrence, Johnson said.
Perhaps the most compelling study was recently published in The New England Journal of Medicine.
The CHALLENGE trial enrolled patients with resected stage II or III colon cancer who had completed their adjuvant chemotherapy. Patients with recurrences within a year of diagnosis were excluded, as they were more likely to have highly aggressive, biologically active disease.
Participants were randomized to receive healthcare education materials alone or in conjunction with a structured exercise program over a 3-year follow-up period.
The focus of the exercise intervention was increasing recreational aerobic activity over baseline by at least 10 METs — essentially the equivalent of adding about 45-60 minutes of brisk walking or 25-30 minutes of jogging three to four times a week.
At a median follow-up of nearly 8 years, exercise reduced the relative risk for disease recurrence, new primary cancer, or death by 28% ( P = .02).
'This benefit persisted — and even strengthened — over time, with disease-free survival increasing by 6.4 and 7.1 percentage points at 5 and 8 years, respectively,' Johnson noted in a Medscape commentary.
The CHALLENGE results are 'very compelling,' Bishal Gyawali, MD, PhD, associate professor of oncology at Queen's University, Kingston, Ontario, Canada, noted in a separate Medscape commentary.
'If you compare these results with results from other trials, you'll see that this is a no-brainer. If this were a drug, you would want to use it today,' Gyawali said.
Saltzman told Medscape Medical News patients often ask him what they can do to help prevent their cancer from coming back. 'I would sort of say, 'Well, eat a healthy diet and exercise,' but I didn't have a lot of good evidence to support it.' The CHALLENGE study provides 'the proof in the pudding.'
With these strong data, 'it almost feels like I should be able to write a prescription for my patient to join an exercise program and that their insurance should cover it,' Saltzman said.
