Molecules aren't the only things that get a makeover - your entire colon gets one too, round by round, every time you show up for your FIT screening. Think of it like a recurring spa appointment for your insides: each session buffs away the sketchy polyps and leaves behind a sleeker, lower-risk you. And a massive new study just dropped the receipts on exactly how dramatic that transformation really is.
2.81 Million People, Seven Rounds, One Wild Dataset
Researchers from Catalonia, Spain, tracked nearly 2.81 million people invited to a biennial (that's every-two-years) faecal immunochemical test (FIT) screening program from 2010 to 2023. FIT is that deceptively simple stool test that checks for hidden blood - the kind you can't see - which can flag polyps or early-stage colorectal cancer (CRC) before things get serious (Ladabaum et al., 2025).
Seven rounds. Fourteen years. Millions of poop samples. Science at its absolute finest.
The First Round Hits Different
Here's where things get spicy. That very first screening round? It's the blockbuster round. FIT positivity peaked at 5.8%, the positive predictive value (PPV) for cancer was 5.1%, and the detection rate clocked in at 2.65 cancers per 1,000 participants. The first round basically sweeps up all the trouble that's been quietly accumulating in colons that have never been screened.
But - and this is the genuinely exciting part - those numbers dropped because the screening was working. By round three and beyond, outcomes stabilized at substantially lower levels. The CRC detection rate in adherent participants by the seventh round? Around 1.6-2.2% PPV at median age 62-65. Compare that to 6.6% PPV for brand-new screeners of the same age who were just stepping into the screening game for the first time. That gap is the glow-up in action: repeated screening strips away high-risk neoplasia and leaves behind a population that's been progressively de-risked.
Nearly Half the People Never Showed Up (Yikes)
The study also revealed a participation pattern that should make public health folks reach for their stress balls. Of those 2.81 million invitees:
- 29.2% were consistent attendees (100% of rounds)
- 8.6% were frequent (66-99%)
- 11.5% were occasional (33-65%)
- 4.5% were infrequent (1-32%)
- 46.2% never showed up at all
Almost half. Nearly half the invited population never completed a single FIT. Meanwhile, prior research shows that European organized screening programs struggle to meet even the recommended minimum participation of 45% (Klabunde et al., 2015). This is a problem because the whole point of population-based screening is that it only works if the population actually, you know, participates.
So Can You Stop Screening After a Few Clean Results?
This is the question that prompted the study, and the answer is a resounding nope.
Some have wondered whether people who've been diligently screening with normal results for years might safely stop early. It's a tempting thought - if you've had several clean FITs, surely your colon is basically a pristine meadow, right? Wrong. Even in the most adherent group, the detection rates remained clinically meaningful through all seven rounds. Cancer kept showing up, just at lower rates.
The researchers put it bluntly: "early screening cessation after a sequence of normal biennial FITs is not justified." Your colon can still grow new troublemakers between screenings. Biology doesn't care about your winning streak.
This aligns with current USPSTF and ACS guidelines recommending continued screening through age 75, with individualized decisions for ages 76-85 (USPSTF, 2021). Meanwhile, the recent SCREESCO trial reinforced that both FIT and colonoscopy improve early-stage CRC detection compared to usual care (Forsberg et al., 2026).
The Silver Lining (It's Bright)
Colonoscopy completion after a positive FIT was 87.3% in this program - an impressively high follow-through rate that many programs would envy. And here's what all the declining numbers actually mean: the system is working exactly as designed. Each round removes the highest-risk lesions, creating a progressively safer population. It's like a bouncer methodically clearing out the rowdiest troublemakers from the club - round after round, the crowd gets calmer, but you still need the bouncer there.
Colorectal cancer remains the third most common cancer worldwide, but it's also one of the most preventable through screening. This study, one of the largest and longest to examine repeated FIT-based screening, gives us the strongest evidence yet that sticking with the program pays off - and that quitting early doesn't.
So if that FIT kit is sitting on your bathroom shelf collecting dust: this is your sign. Your colon's glow-up is waiting.
References
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Ladabaum U, Font Marimon R, Castells X, et al. Effect of long-term adherence on faecal immunochemical test positivity rate, positive predictive value and detection rate in organised population-based colorectal cancer screening. Gut. 2025. DOI: 10.1136/gutjnl-2025-336994. PMID: 41617486
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Klabunde C, Blom J, Bulliard JL, et al. Participation rates for organized colorectal cancer screening programmes: an international comparison. J Med Screen. 2015;22(3):127-136. DOI: 10.1177/0969141315584694
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Jensen CD, Corley DA, Quinn VP, et al. Fecal Immunochemical Test Program Performance Over 4 Rounds of Annual Screening: A Retrospective Cohort Study. Ann Intern Med. 2016;164(7):456-463. PMID: 26811150
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Forsberg A, et al. Colonoscopy and fecal immunochemical testing versus usual care in diagnostic colorectal cancer screening: the SCREESCO randomized controlled trial. Nat Med. 2026. DOI: 10.1038/s41591-026-04225-9
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US Preventive Services Task Force. Screening for Colorectal Cancer: US Preventive Services Task Force Recommendation Statement. JAMA. 2021;325(19):1965-1977. Available at: USPSTF
Disclaimer: The image accompanying this article is for illustrative purposes only and does not depict actual experimental results, data, or biological mechanisms.