Did you know that March is Colorectal Cancer Awareness Month? Cases of this cancer are on the rise among young people: by 2030, it’s projected to be the leading cause of cancer death for people under 50.  

To make sense of risks, symptoms, and screening options, we sat down with Chris Anker, M.D. -- a radiation oncologist specializing in colorectal cancer and co-leader of the Cancer Center’s Cancer Host and Environment Research Program, which explores the relationship between cancers and their host environments. 

Dr. Anker also talked about a study he led in November 2024 – supported by UVM colleagues Dmitriy G. Akselrod, MD (radiology) and Peter A. Cataldo, MD (colorectal surgery) – about treatments for rectal cancer, published in the International Journal of Radiation Oncology, Biology, Physics. That study has since influenced new national guidelines for rectal cancer treatment that focus on quality of life.  

When talking about “colorectal cancer” what part or parts of the body are we talking about?  

Colorectal cancer affects the colon and rectum, which are parts of the large intestine. The large intestine is in the lower belly area and part of your digestive system. The colon is a long tube that helps absorb water and nutrients from food, while the rectum is the last section of the intestine, which stores waste before it leaves the body. Colon and rectal cancers occur when abnormal cells form into a tumor that can block the colon and even invade and damage the surrounding tissues.  

What environmental and lifestyle factors can increase your risk of CRC?  

You can break it up into a few areas such as dietary factors, lifestyle factors and environmental factors.  

Dietary items associated with cancer include red and processed meats. So, high consumption of beef, pork, lamb, bacon, sausages, and hot dogs can increase the risk because of some carcinogenic compounds that are formed during cooking and processing them.  

Low fiber intake has been associated with some risk of colorectal cancer. A diet low in fiber may reduce the protective gut microbiota diversity and increase your risk; while high-fat diets can contribute to inflammation and cause cancers to form.  Excessive alcohol consumption is also associated with the risk of developing cancers because alcohol is a carcinogen, and low vitamin D levels are linked to increased risk as well.   

In terms of lifestyle factors: physical inactivity can cause problems with insulin resistance and inflammation, which contribute to the development of cancers and obesity. Smoking can lead to cancers too. Going back to the gut microbiome: if you're taking a lot of antibiotics, eating a low fiber diet, and have chronic inflammation, those can all contribute to an altered gut microbiome and colorectal cancer.   

Environmental factors also play a role: think prior radiation exposure, or other carcinogens like pesticides that you might have encountered. Conditions in your medical history can also play a role, such as chronic inflammation from Crohn’s disease or ulcerative colitis, which can increase the risk of developing colorectal cancer. And finally, there are certain genetic factors such as Lynch syndrome and Familial Adenomatous Polyposis that greatly increase your risk of developing the disease.  

Who is at risk for colorectal cancer?  

While the older you are, the greater your risk of colorectal cancer, it's a well-recognized fact that more and more young people are being diagnosed with colorectal cancer.  Although having a first degree relative who’s had colorectal cancer increases your risk, more than 80% percent of patients diagnosed with colorectal cancer do not have a family history of the disease. This indicates that while family genetics impact colorectal cancer risk, there are lot of other factors at play. Men carry a slightly higher risk; African Americans carry a higher risk; and people with certain dietary habits or who are morbidly obese also carry a high risk. But you could also be in phenomenal health and do everything seemingly right and still be at risk for colorectal cancer. 

Can you tell us about some symptoms people should keep an eye out for?  

Most early-stage colorectal cancers often present with no symptoms. Even with some of the more advanced ones, you may never even notice anything wrong, which is why it's so important to get screened. 

Some symptoms you might notice are changes in bowel movements -- whether it's more diarrhea or constipation -- that lasts for more than a few days. Bright red blood in the stool could be due to rectal bleeding; while darker red blood in the stool could be from bleeding higher in the colon and is typically more concerning.  

People might notice generalized cramping, bloating, gas, or just some persistent discomfort in the abdomen. Feeling like you frequently need to have a bowel movement even after you just went is a symptom associated typically with rectal cancer because your body thinks that there's still more in there when it's actually a tumor. So, it just might never quite feel like things are normal.  

What screening options are available?  

A colonoscopy is the gold standard because it detects potential cancers as well as polyps, which can be removed during the procedure. A colonoscopy evaluates the entire colon and rectal areas, which is very helpful, and – barring a family history of colorectal cancer or polyps -- it’s typically done every 10 years. However, sometimes the best test is just the one that you’ll actually do. For people who want something less invasive than a colonoscopy (which requires a degree of preparation), there’s a sigmoidoscopy. However, this won’t evaluate the upper parts of the colon, and if it’s your only screening method, it should be done more frequently, like every five years. 

There are other less invasive options. A Fecal Immunochemical Test (FIT test) looks for blood in the stool and doesn’t require prep; however, it does need to be done annually, and if it comes back positive, a colonoscopy is needed. Another option is Cologuard, a multitarget stool DNA test, which detects DNA blood from cancer or polyps and stool samples; that's done every three years. It’s more sensitive than the FIT test, but it also has more false positives than other tests, which could require additional tests that otherwise might not be necessary.  

Other screening options include a CT colonography, which is a CT scan that creates detailed images of the colon, and that can be done every five years. It does require bowel prep, and if polyps are found, then standard colonoscopy would be needed. Finally, there’s a new non-invasive blood test called the Shield test. It detects specific DNA fragments (called cell-free DNA) that are shed into the bloodstream by colorectal cancer or precancerous polyps. A blood sample is collected and analyzed in a laboratory. A positive result indicates the presence of these DNA fragments, suggesting the need for further evaluation with a colonoscopy. 

Let's talk about the study, published in the International Journal of Radiation Oncology, Biology, Physics, which influenced new guidelines for the treatment of rectal cancer. What about these guidelines is different from the old guidelines? (LISTEN: Red Journal Podcast November 15, 2024) 

For decades, we've involved surgery as part of the standard of care for rectal cancer; for more advanced cases, it’s been a cornerstone of management alongside chemotherapy and radiation. But what these guidelines aim to do is encourage people to recognize the quality-of-life benefits with either avoiding radiation therapy for some patients, or surgery for a broader range of patients. The real difference is highlighting and trying to guide providers towards understanding the excellent outcomes with these more quality-of-life-focused therapies and also showing providers how to bring these options to their practice.  

What do you mean when you say, “quality of life”? And how might these new guidelines impact a patient’s quality of life?   

“Quality of life” can mean a broad range of things. Traditionally, we might define quality of life as having fewer side effects, including those impacting bowel function and sexual function. What’s born out in the literature, however, is that patients just want to keep doing the things they like to do every day, whether it’s going for a walk or a kayak ride for a couple hours and not having to worry about running to a bathroom or being uncomfortable while doing those things. And there’s a better chance of being able to continue on as you were in your life if you avoid unnecessary therapies. So, the guidelines really focus on patients only needing one local therapy which is typically combined with chemotherapy for their cancer, whether it's radiation or surgery. 

In terms of the effect these guidelines might have on rural patients: for those who don’t need radiation at all, the number of overall visits decreases because you don't need to come in for what has been traditionally five to six weeks of radiation therapy. However, these guidelines do allow for some flexibility in the radiation regimens, and some patients may be eligible for just 5 days of radiation. For those who avoid surgery, they don’t need to interrupt their lives for the procedure and recovery time. This is important for providers, patients and their caregivers, as they decide what might work best for the patient and allow space for those more convenient options. 

What process did you take to determine these new guidelines? 

Guideline documents such as the ones we worked on don't just evaluate the first few papers that come up in a Google search or research database; they look at all the evidence. So, while an individual doctor might not have time to look through thousands of articles to pick out the best studies, we as researchers will actually do that in what is called a “systematic review”. We go through thousands of references to distill only the best information out there into the framework for which to develop these guidelines.  

We work with a panel of multidisciplinary providers who are experts in their field-- medical oncologists, surgeons, radiation oncologists, radiologists -- to analyze this literature, and we come up with practical, common cases that pertain to almost any rectal patient going to their doctor. And these guidelines highlight all the options that are supported by evidence, so that providers can have more meaningful conversations with their patients about next steps.  

Personally, I think cancer care is at its best when you can provide a menu of options for patients. There's not a one-size-fits-all therapy, and the patient deserves to know their range of options so they can make the choice that’s best for them. 

So much has changed in the last few years to improve quality of life for patients. Where do you see science going in the next 5 or 10 years? 

The advances that I see happening are giving us a better understanding of who may be at risk for colorectal cancer, and I expect that our ability to identify patients who are at risk and who may need more aggressive screening based on their family history and other factors will continue to improve. After all, the best way to preserve that quality of life is to never get cancer in the first place.  

If you are due for a screening, it’s always recommended to talk to your primary care provider about the option that’s best for you. Screening for colorectal cancer increases survival, allows for early detection, and decreases treatment time, should you have the disease.