Colon Cancer Screening

Summary

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Run the List Podcast: Colon Cancer Screening

Hosts: Navin Kumar (with panel), featuring Dr. Sith Saker
Date: February 9, 2026

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Episode Overview

This episode of Run the List delves into the ins and outs of colon cancer screening—a highly relevant topic in both primary care and gastroenterology. Host Navin Kumar is joined by Dr. Sith Saker, a gastroenterologist at Brigham and Women's Hospital, to explore risk stratification, best practices, available screening modalities, technical considerations, and practical pearls for medical trainees and practitioners. The discussion is structured around a common clinical scenario and emphasizes guideline-based, patient-centered care.

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Key Discussion Points & Insights

1. Assessing Family History & Risk Stratification

• First Degree Relatives Are Key:
  Dr. Saker emphasizes that risk assessment for colon cancer hinges on “first degree relatives” (parents, siblings, children).

  “So any first degree relative with colon cancer at any age, then you would begin colonoscopy screening at age 40 or 10 years before the earliest colon cancer diagnosis.” — Dr. Sith Saker [02:00]

• Advanced Polyps = Colon Cancer Risk:
  Advanced adenomas (size >1cm, tubulovillous/villous histology, high-grade dysplasia, or advanced sessile serrated lesions) in a first degree relative should be treated the same as colon cancer in terms of screening recommendations.
• Details Matter:
  It’s important to obtain procedural and pathology reports from family members, as nuances such as polyp size and histology change the risk calculation.

Memorable Moment:
Navin highlights the two precancerous polyp types—adenomatous and serrated—and that both necessitate the same increased vigilance [03:02].

Clinical Scenario Application

• If the relative had only a small adenoma (<1cm), with no other high-risk features, the patient reverts to average risk (screening at age 45).
• Earlier screening is warranted if advanced polyps or cancer were diagnosed at a young age in the family (screening starts at age 40 or 10 years before the relative’s diagnosis).

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2. Screening Modalities: Prevention vs. Detection

• Two Main Approaches:
  • Colonoscopy: Preferred for its diagnostic and therapeutic potential; visualizes the full colon and can immediately remove precancerous lesions. Typical interval: every 10 years if normal [04:31].
  • Stool-Based Testing:
    • FIT (Fecal Immunochemical Test): Annual or biennial. Non-invasive, completed at home.
    • Multitarget Stool DNA (Cologuard): Completed at home, detects blood or abnormal DNA, but cannot prevent cancer by removing polyps.

“Both are guideline-endorsed. Neither is better than the other and the effectiveness of either strategy depends heavily on patient adherence.” — Dr. Sith Saker [04:31]

• Caveat: Any positive stool-based test requires prompt follow-up colonoscopy.

Other Modalities

• CT Colonography:
  • Used mainly when colonoscopy can’t be completed (anatomic, technical, or patient factors).
  • Non-invasive, requires bowel prep, can’t biopsy or remove lesions; misses some flat/small lesions.

  “Its highest value is as a completion study after an incomplete colonoscopy.” — Dr. Sith Saker [06:32]

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3. Bowel Preparation: Critical for Quality

• Practical Insight:
  A split-dose Miralax-based bowel prep is described as the institutional standard (half dose the evening before, half five-to-six hours pre-procedure), optimizing visualization.

  “It’s paramount of importance. It really helps in making sure that there’s no small polyps or lesions missed...” – Dr. Sith Saker [08:32]

• Consequences of Poor Prep:
  Poor bowel prep may necessitate repeating the colonoscopy earlier than the default 10 years, reducing the test’s effectiveness and causing extra burden for the patient [08:32].

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4. Colonoscopy Technique & High-Risk Areas

• Blind Spots and Critical Areas:
  • Ileocecal valve
  • Right-sided colon/cecum: High risk for flat, sessile serrated lesions
  • Hepatic flexure (the ‘blind spot’)
• Best Practices:
  • Multiple careful passes over high-risk areas (e.g., 2–3 times at hepatic flexure)
  • Dedicated time for withdrawal (≥8–10 min withdrawal time recommended)

  “Our metrics, our quality metrics are always sort of improving. Now we're trying to hit at least 10 minutes, 8 to 10 minutes on withdrawal ... these lesions can be very small and very flat and very easy to miss.” — Dr. Sith Saker [09:38]

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5. Pearls and Take-Home Points

RTL Pearls by Dr. Saker [11:28]:

• Always obtain a detailed family history—including polyp pathology when possible.
• Advanced adenomas (as defined) in a first-degree relative confer the same risk as colon cancer (screen at age 40 or 10 years prior to relative’s diagnosis).
• Colonoscopy is both diagnostic and preventive, but the best strategy is the one the patient will complete.

  “The best strategy is the one that the patient is going to follow.” — Dr. Sith Saker [12:57]

• Any positive stool-based test must prompt a diagnostic colonoscopy.

Navin’s Closing Thought [12:57]:

“The ability to screen for colon cancer is so, so important ... the best screening strategy is the one that your patient is going to follow through with.”

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Notable Quotes & Moments

• On risk stratification and family history:
  “Always think about advanced polyps as the same as colon cancer.”
  — Dr. Sith Saker [02:00]
• On the importance of prep:
  “It just sort of makes the whole procedure much more comfortable ... if the preparation is not great, sometimes we have to repeat the colonoscopy ...”
  — Dr. Sith Saker [08:32]
• On the best screening test:
  “If they're reluctant to get a colonoscopy but will undergo stool testing, I think it's important to discuss that with them ... the best strategy is the one that the patient is going to follow.”
  — Dr. Sith Saker [11:28, 12:57]

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Useful Timestamps

• 01:02 – Episode kickoff, guest introduction
• 02:00 – Family history and risk stratification
• 04:31 – Discussion of screening methods
• 06:32 – CT colonography: special cases
• 07:31 – Bowel preparation protocols
• 08:32 – Impact of prep quality
• 09:38 – High-risk anatomical areas in colonoscopy
• 11:28 – Pearls and summary

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Final Takeaway

This episode provides a comprehensive, pragmatic overview of colorectal cancer screening, balancing concise guideline-based advice with real-world insights on patient adherence and procedural quality. Key message: Know your patient's true risk, choose a screening approach they will follow, and uphold high standards for colonoscopy quality to maximize preventive benefit.

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Transcript

[Host]

Welcome back to Run the List, a medical education podcast in internal medicine. As a quick disclaimer, this podcast is made for educational and informational purposes only and should not be understood as medical advice under any circumstances. Before we get to the show, a quick word on the sponsors for today's episode.

[Sponsor Representative]

This episode is brought to you by Open Evidence. Open Evidence is a really incredible resource for people in medicine. It's an AI powered medical information platform that can help you answer clinical questions, provide high quality literature and so much more. You can ask questions like what are the classic imaging findings for gout? Or Tell me about the landmark trials in lupus nephritis. They recently partnered with the New England Journal of Medicine so they have access to their text, figures and tables within Open Evidence. It's free and unlimited for healthcare professionals, so I highly encourage you to go check it out. Go to openevidence.com to learn more.

[Navin]

Welcome back to Run the List. Today we will be discussing a very high yield topic for primary care and one we know very well in the field of GI and that is colon cancer screening. We are joined by Dr. Sith Saker who is a general gastroenterologist at the Brigham Women's Hospital and who has a particular interest in medical education. Sith, thank you so much for joining us today.

[Dr. Sith Saker]

Thanks Navin. It's an honor to be on the Run the List podcast and to help teach about this very important topic today with you.

[Navin]

Same here Sith. So let's go ahead and run the list. Let's start by setting the stage. In primary care clinic you are seeing a 40 year old healthy male with no past medical history. As you are obtaining a family history, he mentions he had a paternal grandfather who passed away from colon cancer in his 80s and he believes his mother had a colon polyp removed recently as well. He asked if he needs to start colon cancer screening at an earlier age because of this family history. Sif, how do you think about estimating risk for colon cancer in the context of family history?

[Dr. Sith Saker]

That's a great question. When I think about family history, I think it's really important to think in the first degree relatives. That's what's really important. So any first degree relative with colon cancer at any age, then you would begin colonoscopy screening at age 40 or 10 years before the earliest colon cancer diagnosis. The other thing that's important is to sort of figure out polyp history in your family and ideally obtain procedural and pathology reports of the family member, especially if there's concern for an advanced Polyp, you're particularly concerned about any polyp that's greater than 1cm in size that has tubul villus histology or villus histology high grade dysplasia, or any advanced SL serrated lesions. And then in that case, you would think of it in the same way that you would as colon cancer and begin screening at age 40 or 10 years before the diagnosis. So you always think about advanced polyps as the same as colon cancer, and in both those cases, you would start at age 40 or 10 years before the diagnosis.

[Navin]

So, Seth, those are such important points. It's so critical to get a detailed family history and to remember, not just ask about colon cancer, but also advanced polyps. And when you were discussing the advanced polyps, I liked how you broke it down between advanced adenomatous polyps and advanced sessile polyps as well, because there are two different types of precancerous polyps, and both of those, if they have those characteristics that you said will constitute an advanced polyp and also a positive family history. So in this case, let's say the patient finds out this mother had just a small adenoma, let's say it was like 3 millimeters that was removed, so below that 1 centimeter threshold. And no other first degree relatives with colon cancer or advanced polyps. So based on this information, when would you recommend he start colon cancer screening?

[Dr. Sith Saker]

Yeah. So based on the current guidelines, he'd be considered average risk for colon cancer and should start screening at age 45. But, you know, for example, if the mother, she had a 3 millimeter polyp, but if it was sort of 1.5 centimeters or had any of those advanced features and she was diagnosed with that polyp at even age 35, then you would think about starting at 25 for him. If it was diagnosed at 60, then you would think about starting At 40 for him.

[Navin]

Perfect. So you basically just take the earliest time, whether it be age 40 or 10 years before the age of diagnosis, like he just went through. All right, so now that we discussed when to start screening, what are the options available to screen for colorectal cancer?

[Dr. Sith Saker]

So there's, there's a ton out there. And when I think about counseling patients for colorectal cancer screening, I try to frame it around prevention and adherence. And like we discussed before, colorectal cancer typically develops either from adenomatous or serrated polyps over many years, which gives us a great window to either remove precancerous lesions or detect cancer early when outcomes are the best. So for Average risk adults, which is very important. So no prior history of polyps and no family history. As we discussed prior, there are two broad based screening strategies. Either you can go with colonoscopy, direct visualization or stool based testing. Both are guideline endorsed. Neither is better than the other and the effectiveness of either strategy depends heavily on patient adherence. Colonoscopy is the most comprehensive option. It visualizes the entire colon and allows for immediate pulp removal, which is why it's considered both a screening and preventative test and one that we usually prefer. A normal exam generally allows for 10 year interval before the next one. The trade offs though are that you do need to go through that bowel preparation, need for sedation, a small but real risk of complications such as bleeding or perforation outcome perspective. It offers the lowest risk of interval colorectal cancer when performed with good quality metrics. The other big group are the stool based tests such as fit testing or cologuard, which is a multi targeted stool DNA testing. They're non invasive and completed at home which improves patients doing it. These tests detect occult blood or abnormal DNA shed by the advanced adenomas or cancer. Their key limitation is that they do not prevent the cancer and they do not remove any polyps. And they require strict adherence to repeat testing at regular intervals. But the most important point is that any positive stool based test mandates a short interval diagnostic colonoscopy and that's really important for patients to understand.

[Navin]

Sif, that was a really helpful overview of the available screening tests and the guidelines behind which tests to choose. Are there any other screening tests that you use in certain patients or scenarios that we have not yet discussed?

[Dr. Sith Saker]

Yeah, one that comes up from time to time is CT colonography. It's actually most commonly used when a colonoscopy is incomplete or technically not feasible to do. This can happen when there's a redundant or very tortuous colon, fixed angulations from prior surgeries or patient intolerance from sedation or from the procedure. It provides a non invasive cross sectional evaluation of the entire colon. It can identify clinically significant polyps, typically those that are greater than 5 millimeters, but unfortunately can't really identify any of those really flat lesions that sessile serrated polyps can be, or any polyps less than 5 millimeters. The key limitations are that it still does require bowel preparation like a colonoscopy, but doesn't allow for biopsy or polyp removal. And any concerning findings still require follow up colonoscopy. In practice, its highest Value is as a completion study after an incomplete colonoscopy to avoid any missed proximal lesions from where you couldn't get past.

[Navin]

Excellent. I think it's helpful just to review the bowel preparation since you've mentioned it a few times, both with obviously colonoscopy, but as well as CT colonography. And so in our institution and most other institutions, this involves being on a clear liquid diet the day prior to the exam and then towards the later afternoon to start the actual bowel preparation. Our standard is to use a Miralax based preparation in which the patient takes a full bottle of Miralax and mixes it in 64 ounces of clear fluid. And we found that actually the split preparation, where they then split the dose between doing 32 ounces of that prep that afternoon and then the second 32 ounces five to six hours before the procedure, leads to better visualization for the colonoscopy. So it indeed it is a to do for the patients to accomplish before their exam. And Seth, can you comment about the importance of having a CLE bowel preparation for the colonoscopy?

[Dr. Sith Saker]

Yeah, it's paramount of importance. It really sort of helps in making sure that there's no small polyps or lesions that are missed. And it just sort of makes the whole procedure much more comfortable for the patient as less time is used, sort of getting through the colon and it gives such a cleaner view while looking at the colon sort of on withdrawal and looking for polyps. And you know, unfortunately, if the preparation is not great, sometimes we have to repeat the colonoscopy in short interval or are not able to clear them for that full 10 years that we ideally like to if it's a normal colon. So while it is sort of, you know, an undertaking for the patient to undergo right before the colonoscopy, it's so important to do it very carefully and well.

[Navin]

Absolutely. And I love how you touched on the quality metrics of a colonoscopy. I think in addition to having an adequate bowel preparation, so much of this hinges on the endoscopist taking their time when surveying the colon, looking in between folds and. And Seth, you can, you can comment on this. Where are the most high risk lesions often missed during a colonoscopy? And why do we pay special attention to that area of the colon?

[Dr. Sith Saker]

Yeah, so there's a couple places I really pay careful attention through the colon because it's so easy to miss lesions or polyps there. One of them is right behind the ileocecal valve. Right. That the end of the colon sort of polyps can definitely be flat and sort of right behind there. And on the right side are the ascending colon and the cecum. There's definitely a higher risk of having sessile serrated lesions, which are sort of these flatter lesions that are much easier to miss. And then the other big spot is right at the hepatic flexure, right where that turn is made into the ascending colon. Just because it's sort of a blind spot, as if you're driving, it's sort of a blind spot on a colonoscopy. So really taking time, looking at that area at least two to three times with careful withdrawal, and then spending sort of adequate time withdrawing throughout the whole colonial. Our metrics, our quality metrics are always sort of improving. Now we're trying to hit at least 10 minutes, 8 to 10 minutes on withdrawal. And that's really important because these lesions can be very small. They can be very flat and very easy to miss. So taking your time is really important during a colonoscopy.

[Navin]

That's great, Seth. Yeah. When I have medical students come shadow me an endoscopy, I know I have them shadow you as well. I think they're always surprised by how small and subtle some of these polyps are. So it truly takes an experienced eye but just extra time to find these lesions that can otherwise be potentially missed. So this was great. I want to get back to our case, and let's review. So based on your knowledge of the guidelines, you recommend that this patient start colon cancer screening at age 45, as he's considered average risk for CRC. Together, you decide on a plan for a screening colonoscopy. At that time, as he is a healthy candidate and he's motivated to undergo a diagnostic and potentially therapeutic procedure. He also feels reassured by his average wrist status after your review of the guidelines. So with that sith, can you conclude our episode with some RTL pearls from today?

[Dr. Sith Saker]

Absolutely. I think the biggest pearl, and one that's really important to understand, is that it's important to learn your patient's family history. You know, obtaining any patient's family's procedure and pathology reports if needed. A lot of times, sort of, those advanced adenomas can be missed in the patient's family history, as it's not something often mentioned to children. Colon cancer patients usually know their family history of but those advanced adenomas into review. Anything that's greater than 1cm in size has tubulo villus or villus histology. High grade dysplasia or any sort of advanced sessile serrated lesions are really important to know because that puts them at sort of the same risk as having colon cancer in their first degree relatives would and starting screening at age 40 or 10 years before the diagnosis. So that's a really important pearl to understand. And then it's, you know, there are a lot of different colon cancer screening strategies. Colonoscopy provides both that screening and diagnostic aspect of removing the polyps and lesions at the time of the procedure, but understanding that the best strategy is the one that the patient is going to follow. So if they're reluctant to get a colonoscopy but will undergo stool testing, I think it's important to discuss that with them. Talk between fit and sort of DNA based, such as cologuard, do it at the appropriate intervals and you know, most importantly, if it does become positive, refer them for that colonoscopy so that we can do more of a diagnostic look to try to see, you know, why it turned positive. If there's a large polyp or anything like that that needs to be removed.

[Navin]

Those are some great pearls, Seth. And you know, I do think the bowel preparation is the most challenging piece of the experience for patients. And when I have patients who come see me for the first time for their colon cancer screening and colonoscopy, it's often that first step of just getting through the prep and then once they're actually here for the procedure, everything like you said, provided that it is done carefully and with high quality, goes very smoothly almost all the time. So the ability to screen for colon cancer is so, so important. So I really appreciate you going through all the different options and especially that take home point that the best screening strategy is the one that your patient is going to follow through with. So thank you so much, Sif. This was great. We had such a nice time discussing colon cancer screening in depth with you and I look forward to having you back on RTL in the future.

[Dr. Sith Saker]

Thank you for having me.