An interview with Paul J. Limburg, M.D. conducted by April Cashin-Garbutt, MA (Cantab)
What is colorectal cancer? How does colon cancer differ from rectal cancer?
Colorectal cancer is a combined term to describe the malignant tumors that occur in the large intestine; the colon being the upper part of the large intestine and the rectum being the lowest part of the large intestine.
Colorectal cancer is ranked as the second leading cancer killer of both men and women in the United States, when you combine the numbers for those specific gender groups. We believe this is a major public health issue.
The good news is that many colon cancers can be prevented or caught early if we follow regular screening protocols and there are multiple tests that have been shown to be effective both for screening and early detection in colon cancer.
What are the different stages of colorectal cancer and when is it usually diagnosed?
Colorectal cancers are typically categorized as stages I through IV. From a practical standpoint, patients can present with pre-malignant colorectal tumors (called adenomas), early stage I colorectal cancers, all the way through to later stage IV disease.
Colorectal cancer often doesn't have any symptoms associated with it and, unfortunately, if people don't adhere to regular screening, even when they don't have symptoms, they may end up presenting with a later stage colorectal cancer.
Who is most at risk for colorectal cancer?
The single biggest risk for colorectal cancer is age. The majority of cases occur after the age of 50. That's why many of the screening guidelines use age 50 as a threshold to initiate screening in the absence of any other identified risk factors.
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Another factor that has a major influence is family history. If somebody has multiple family members with colorectal cancer, they are at an increased risk. There are also some inherited or heritable syndromes that can have different types of cancers, where colorectal cancer is also at an increased risk, so family history is very important.
There are some medical conditions such as inflammatory bowel disease, which includes Crohn's disease and ulcerative colitis, that cause a long-standing inflammation in the colon and rectum and that can predispose to developing cancers in those locations.
More and more evidence is emerging to suggest that diabetes, particularly type II diabetes, is a potential risk factor for colorectal cancer.
There are also some environmental exposures. Smoking seems to have an impact, at least on a subset of colorectal cancers. Body size also seems to influence risk, maybe through metabolic syndrome and diabetes, which are commonly linked with insulin resistance that can promote tumor growth in the colon and rectum. The science is a little bit less mature with respect to some of those areas, but I think it's continuing and is becoming more and more consistent.
The good news is that some protective things may also be available and useful. Physical activity has consistently been shown to lower the risk for colorectal polyps and cancers. There are some dietary habits that seem to be better for trying to prevent the disease such as eating wholegrain fruits and vegetables and avoiding highly processed foods and excess red meat, especially red meat with a heavily charred surface. Those sorts of dietary patterns can all help to protect against colon and rectal cancer.
Lastly, there are fairly striking data to suggest that some medications such as nonsteroidal anti-inflammatory drugs can also lower the risk. Aspirin is probably the best known of that class, although it should only be taken in consultation with a physician because, as with any medicine, even those fairly common medicines can have some side effects.
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How many people does colorectal cancer affect?
Based on US data, the estimated new cases in 2017 is just under 100,000 for colon cancer and about 40,000 for rectal cancer. The number of deaths as a result of colorectal cancer is about 50,000 per year.
Is screening helping to prevent deaths from colorectal cancer?
Absolutely. Some of the data are tough to obtain because, as with anything in medicine, sometimes the practice gets out ahead of the science. I think that due to some of the early studies demonstrating that there is a benefit from some screening tests, screening has now become much more widely accepted, so it's difficult to organize and conduct randomized, controlled trials of all the available screening test options.
Having said that, the evidence that colorectal cancer screening provides benefits is substantial. Findings from a US study reported as far back as 1993, called 'The National Polyp Study', demonstrated that, compared with historical controls, individuals who underwent colonoscopy had anywhere from a 76% to a 90% decrease in their risk for colorectal cancer when they had colonoscopy with polypectomy, which is the removal of precancerous polyps. I think that's just one example of studies that have shown very striking findings to support that screening for colorectal cancer can have a major impact.
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What screening options are available?
There are several different endorsed options, including some tests that can detect precancerous conditions and cancers and other tests that primarily detect cancers.
Colonoscopy is an endoscopic procedure. Patients typically take a cleansing preparation prior to colonoscopy to clear out the large intestine. Most often, they're sedated for the exam and the endoscope is passed all the way to the beginning of the large intestine and there's a careful examination on withdrawal of the scope. That's the procedure that can not only detect precancerous polyps or early stage cancers, but can also remove those polyps or biopsy those cancers. One major advantage of colonoscopy is the ability to actually remove or sample the identified lesions that are found during the screening exam.
There's a test called CT colonography or virtual colonoscopy, which is an x-ray exam where, again, the entire colon is examined after a bowel preparation. That one does not require sedation.
There are stool-based tests and those can be divided into three different categories. Two of them detect blood. The test that's been around the longest is the guaiac based fecal occult blood test. That one can have more false positives and false negatives. It requires some dietary and medication restrictions prior to obtaining the sample.
There's a newer category of tests called fecal immunochemical tests or FIT tests. Those involve antibodies that target hemoglobin components, so they are more sensitive and specific for blood in the stool. Then there are some stool-based tests that also look for DNA fragments and that's called stool DNA testing.
All of those different test options have their strengths and weaknesses or advantages and disadvantages. Which test is right for you is a conversation that an individual should have with their clinician.
Can you please explain the national “80% by 2018” initiative?
Colorectal cancer is a topic that many people and even patients are not comfortable talking about, so I think, for a lot of different reasons, colorectal cancer screening rates have lagged behind some other types of screen-detectable cancers such as cervical cancer and breast cancer. We're trying to just make the conversation more available and more acceptable for people to talk about with their physicians, family and so on.
Colorectal cancer screening rates have continued to improve. There have been some shifts in the science and in insurance coverage in the US and other areas of the world that have contributed to that. There have been some celebrity campaigns with Katie Couric and others that have really helped to get the word out about colorectal cancer and the effectiveness of screening.
However, based on US figures, the colorectal cancer screening rates are anywhere in the range of 65 to 70% of the eligible average risk population. The campaign, 80% by 2018, is trying to increase that by a further 10 to 15%, to get 80% of the eligible population adherent with guidelines by 2018 and I think we're seeing signs of success.
There are over 1,000 organizations that have signed on to the effort and we hope in the last year here we can really accelerate and get even more groups and individuals engaged with the program.
What more needs to be done to encourage people to get screened?
It starts with awareness. I think people need to understand what colorectal cancer is. I think they also need to be aware that there are some myths out there such as it only being a man's disease. That is not true.
Another is that if a person doesn't have symptoms, they don't have colorectal cancer. Unfortunately, that's not always true. I think education and dispelling some of those incorrect assumptions is a good place to start.
Then, I think breaking down some of these social barriers is important - just being able to talk about colorectal cancer, since it is highly preventable, and have the conversation, again, with family members because that's such an important risk factor.
People should be able to have a conversation with their physician or nurses and say "Tell me about this and what can I do to lower my risk for colorectal cancer, either through screening, or screening plus lifestyle change etc."
Then I think making sure that the clinicians have the expertise, the access and the understanding of the different screening options is important. In some ways, it's a blessing and a curse to have multiple options that can be used for colorectal cancer screening because it makes the conversation slightly more difficult to have in the short time that a patient and their clinician spend together, but there really is no one right answer. It's which one of these endorsed screening options is the right one for a particular individual?
How are Fight Colorectal Cancer helping to raise awareness of colorectal cancer?
Fight Colorectal Cancer (Fight CRC) is an advocacy group that has been doing a great job. They have been connecting health professionals with patients and with other partners who are developing some of the newer technologies and so on.
I think they are a fantastic group to help connect conversations, to bring some of those education pieces out and to use the power of celebrity. I think they are using creative and innovative ways to help raise the level of conversation, awareness, and, hopefully, the level of screening participation.
What We Do at Fight Colorectal Cancer
What resources do Fight CRC have available to support patients and caregivers?
There are education resources, digital resources and a regular publication with good information that Fight CRC puts out.
From a general perspective, I think they've got lots of quality education materials and that they've been a tremendous partner for any group that would want to engage with them to help organize campaigns that might need local/regional or national/global opportunity.
I think they have been doing a great job all the way from the education materials that they produce or can provide, to connecting to new and unique initiatives that help to raise awareness in creative ways.
What do you think the future holds for colorectal cancer?
Screening is effective for preventing and detecting this disease early and I think that the biggest barrier right now is participation. In some ways, we’ve got a solution to the problem now. We just need to make sure that everybody is aware of, has access to and understands how to best use the screening solution.
I do think that some of these other considerations such as family history and lifestyle are critically important, but I think if we could get people more engaged with screening, we will continue to see colorectal cancer incidence and mortality rates decline because we can both prevent the disease and catch it at an earlier stage when people do participate.
I hope the future state for colorectal cancer is that the number of new cases and the number of colorectal cancer deaths continues to drop and that we do that in a way that allows people to understand that this is just another opportunity that they have to stay healthy and happy for a longer period of time.
Do you think reimbursement is an issue that’s preventing people from getting checked?
It's complex, as with anything in healthcare. I think it would be good if we could turn the discussion into something positive where can we make improvements, rather than making it about what's broken. Simply put, it would be good to get more people engaged.
We know that there are effective options, but we know that adherence with all of these different screening opportunities is lower than we would like. If we can boost that adherence, then I think some of these other pieces of the equation may have less influence.
We need patients, providers, payers, advocacy groups and industry partners. We need everybody to join us in the effort because that's how we can make the advances that will allow us to do a better job of preventing what is truly a preventable disease, at least, in large part.
I think the more we can get the word out there, the more we can make sure that all the stakeholder groups are communicating with each other and that's how I think we'll continue to accelerate progress.
Where can readers find more information?
About Paul J. Limburg, M.D.
Paul J. Limburg, M.D., is a consultant in the Division of Gastroenterology and Hepatology, with a joint appointment in the Division of Preventive, Occupational and Aerospace Medicine. He is a professor of medicine in the College of Medicine, Mayo Clinic.
He is also the medical director of Mayo Clinic Global Business Solutions, medical director of the Dan Abraham Healthy Living Center,principal investigator of the Cancer Prevention Network, and is also a Medical Advisory Board member for Fight CRC.
Dr. Limburg's clinical and research interests are focused on chronic disease prevention, with specific emphases on chemoprevention, molecular epidemiology and early detection.
Focus areas
- Investigation of exposures associated with molecularly defined colorectal cancer subtypes
- Clinical evaluation of novel colorectal cancer screening technologies
- Conduct of early-phase chemoprevention trials through a multicenter, National Cancer Institute-sponsored consortium with participating sites across the U.S., Canada and Puerto Rico
Significance to patient care
The overall goal of Dr. Limburg's translational research is to develop novel, clinically applicable interventions to reduce the public health burden associated with cancer and other chronic diseases.
Professional highlights
- Induction into the American Society for Clinical Investigation, 2011
- Recognition as a Fellow, American Gastroenterological Association, 2011
- Spirit of Collaboration Award, Minnesota Cancer Alliance, 2008
- Laurel Award, Prevent Cancer Foundation, 2005
Liver cells effectively serve as immune checkpoint regulating anti-cancer immunity