New Guidelines for Colorectal Cancer Detection

At just 31 years old, Adrian Ford began experiencing some mild abdominal discomfort. It wasn’t severe; no blood in her stool, no nausea, and no weight loss. Active and healthy, she had even had routine medical checkups just six months earlier that showed nothing alarming. But when the discomfort didn’t fade and she noticed a small lump, she decided it was time to visit the emergency room.

“I thought they had made a mistake. I couldn’t believe the scan was mine,” she recalled. To her shock, she was diagnosed with stage 4 colorectal cancer that had already spread to her liver. “Among the three cancers they suspected—pancreatic, stomach, or colon—I actually felt relieved when they identified it as colorectal cancer because I thought that meant the odds were better,” she said.

Given this scenario, the American Cancer Society (ACS) has updated its guidelines regarding the early detection of colorectal and rectal cancer. For the first time, they have included blood tests as a supplementary screening option. This change, announced in the journal *CA: A Cancer Journal for Clinicians*, is based on a detailed examination of studies about how new screening methods might influence both disease management and outcomes.

However, the ACS clearly states that blood tests are not the first choice currently. Colonoscopies and stool-based assessments still hold the mantle as the most effective screening methods. The reasoning here is that blood tests tend to be less effective in pinpointing precancerous polyps or catching cancer in the early stages. According to the new guidelines, blood tests can be a fallback for those who are unwilling or unable to undergo standard colonoscopy or stool testing.

“Blood tests aren’t the first choice,” explained Dr. William Dahut, the ACS’s chief scientific officer, in a conversation with CNN. “There are many individuals who either cannot undergo a colonoscopy or are reluctant to provide a stool sample. Having more options can help increase screening rates, leading to earlier cancer detection and potentially more patients being cured.”

The updated guidelines recommend that adults aged 45 and older, who are at average risk, get screened regularly. Suggested methods include high-sensitivity stool tests or visual screenings based on personal preference and availability. These methods encompass, but aren’t limited to, colonoscopy every 10 years, virtual colonoscopy every five years, flexible sigmoidoscopy every five years, annual FIT or high-sensitivity fecal occult blood tests, and multi-target stool DNA tests every three years.

Blood tests, particularly the Shield test developed by Guardant Health, are meant for individuals who either refuse or don’t undergo preferred screening methods. Medical professionals should inform patients that blood tests are less effective in spotting serious precancerous changes or early cancer, and a positive result will necessitate a follow-up colonoscopy.

The ACS guidelines do not include high-risk individuals—those with personal or familial histories of colorectal cancer, advanced polyps, inflammatory bowel diseases, genetic syndromes linked to cancer, or previous abdominal radiation. They also apply to asymptomatic individuals. Dr. Dahut emphasized that symptoms such as bleeding, abdominal pain, or changes in bowel habits require immediate evaluation through colonoscopy rather than relying solely on blood or stool tests.

Data presented in the ACS guidelines reveal that the rate of colorectal cancer among people under 50 has surged by approximately 3% each year from 2013 to 2022. Rates among adults aged 50 to 64 have also risen, albeit more modestly, at 0.4% per year. Furthermore, the incidence of rectal cancer has grown by about 1% annually since 2018, now accounting for close to one-third of all colorectal cancer cases.

In fact, colorectal cancer has become the leading cause of cancer-related deaths for men under 50 in the U.S. and the second most common among younger women. Expected statistics for 2026 forecast around 158,850 new cases and nearly 55,000 fatalities.

While the ACS reduced the age for recommended screenings from 50 to 45 in 2018, the participation rates among younger adults have remained relatively low. By 2023, only 37% of those aged 45 to 49 reported being up to date with their screenings, in contrast to 55% of individuals between 50 and 54.

Researchers believe one of the reasons for the push toward new screening options is to boost participation. Studies indicate that providing multiple choices can improve compliance; after all, the most effective test is the one that gets completed.

The primary blood test outlined in the new guidelines, Shield by Guardant Health, gained FDA approval in 2024 and is covered by Medicare. It identifies fragments of tumor DNA in the blood linked to colorectal cancer and is available once every three years.

The extensive ECLIPSE study used almost 8,000 participants from over 200 medical centers across the U.S. All subjects also underwent colonoscopy to serve as the benchmark for comparison.

Results from the study indicated that the blood test detected 83.1% of colorectal cancer cases overall. Yet, its ability to identify early-stage disease was less impressive: sensitivity for stage 1 cancer was only 64.7%, while it reached 100% for later stages.

A significant drawback is its limited effectiveness in identifying polyps and precancerous lesions—changes that could eventually lead to cancer. The ECLIPSE study found that only 13.2% of advanced precancerous lesions were detected by the blood test. Another study, called PREEMPT CRC, assessed a different blood test by Freenome, achieving just 12.5% sensitivity for advanced lesions and remained under FDA review at the time of publication.

Researchers have highlighted that this limitation is critical; much of the benefit derived from screening is attributed to early identification and removal of these precancerous polyps before they evolve into cancer. Modeling studies referenced in the guidelines suggest that roughly 80% of the long-term advantages of screening come from finding and removing these lesions.

Consequently, blood tests aren’t viewed as a preferred method of screening. The ACS suggests they might be beneficial mainly for individuals who would not undergo colonoscopy or stool testing since some screening is better than none.

Dr. Shira Shor, a gastroenterologist, pointed out that blood-based tests are becoming increasingly popular in oncology. “These technologies are expanding into various fields, including early detection in oncology,” she stated. “We are starting to see them applied for cancer prevention as well.”

However, she emphasizes a crucial difference between these new blood tests and existing screening options. “The American Cancer Society mainly suggests these tests for people who, for various reasons, skip routine screening. They’re focused on the early detection of existing cancer rather than on prevention. Early detection is very critical, but often, the disease can actually be prevented.”

It’s important to note that the majority of colorectal cancers start as polyps that can be eliminated. “If you find and remove them early, you can prevent cancer from developing,” she added.

Colonoscopy remains the most effective prevention method, according to her. “This is one of the few types of cancer that can genuinely be prevented,” she explained. “The challenge is that we often miss the opportunity for early detection. There’s no reason that close to 3,000 new cases should be diagnosed in Israel annually when this disease is frequently preventable.”

Updated recommendations also include stool-based tests with higher sensitivity, alongside colonoscopy. Dr. Shor advises that individuals should be aware of their own risk levels, particularly family history, which can significantly elevate risk.

Alongside blood tests, the new guidelines incorporate modern molecular stool tests like ColoSense and Cologuard Plus, which are at-home tests that analyze stool samples for biological indications linked to colorectal cancer.

One significant study on ColoSense, involving over 14,000 participants, demonstrated that it detected 94.4% of colorectal cancers, a sharp improvement from the standard FIT test’s 77.8%. It also identified every stage 1 cancer in the sample compared to around 71% for FIT. In terms of advanced precancerous lesions, ColoSense showcased 45.9% sensitivity compared to FIT’s 28.9%.

Researchers do note a trade-off: lower specificity results in more false positives and consequently more necessary follow-up colonoscopies for people who do not have significant diseases.

Cologuard Plus was evaluated in a study involving over 26,000 participants, achieving 93.9% sensitivity for colorectal cancer and 43.4% sensitivity for advanced precancerous lesions. The updated guidelines now recognize these stool DNA tests as preferred screening options every three years.

Experts are optimistic that blood tests could enhance screening rates, especially among people hesitant to undergo colonoscopies or stool tests. According to Guardant Health, more than 90% of individuals complete their screenings when offered a blood test versus only 28% to 71% for colonoscopy or stool approaches. However, guideline authors caution that real-world data remains sparse, particularly regarding long-term adherence and follow-up rates following positive results.

Surveys included in the guidelines reveal that 53% of participants would select a blood test every three years compared to 32% who opted for annual stool testing and 16% who preferred a colonoscopy every ten years.

In summation, the ACS recognizes newer stool DNA tests as part of the preferred screening arsenal for colorectal cancer. However, blood tests are not yet deemed a satisfactory substitute for colonoscopy or stool-based screenings but do serve as an option for those otherwise remaining unscreened.

The essential takeaway is clear: any positive result from a non-colonoscopy test—whether through blood or stool—requires follow-up colonoscopy, ideally within six months.