A New Option Could Help More People Catch a Deadly Cancer Early
Colorectal cancer is one of the most preventable forms of cancer, yet it remains one of the deadliest when it is discovered too late. Every year, more than 50,000 Americans die from the disease, even though screening can often detect it before it becomes life threatening. Now, the American Cancer Society (ACS) has updated its screening guidelines to include a new blood test as an option for people who avoid traditional screening methods.
The change reflects a simple reality. About one in three adults who should be screened for colorectal cancer have not been tested as recommended. By making screening easier, experts hope more lives can be saved.
What Is Colorectal Cancer?
Colorectal cancer begins in the colon or rectum, usually developing slowly over 10 to 15 years. It often starts as small, precancerous growths called polyps that can be removed before they become cancerous.
“When detected early, survival rates are excellent,” said Dr. Tiago Biachi, a medical oncologist specializing in gastrointestinal cancers.
One of the most concerning trends is that colorectal cancer is increasingly affecting younger adults. It has become the leading cause of cancer death in Americans under age 50, and approximately one in five colorectal cancers is now diagnosed in people younger than 55. Many of these cancers are found only after they have reached an advanced stage, making treatment more difficult.
Doctors believe factors such as obesity, low physical activity, diets high in processed foods and red meat, increased alcohol use, and changes in the gut microbiome may all contribute to the rise, although the exact cause remains unknown.
Traditional Screening Methods
Until now, people at average risk generally had two primary screening choices beginning at age 45.
The first is the colonoscopy, which remains the gold standard. During the procedure, doctors use a flexible camera to examine the entire colon and rectum. If polyps are found, they can be removed immediately, preventing cancer from developing. Because of its effectiveness, a normal colonoscopy only needs to be repeated every ten years.
Several stool-based tests are also available. These tests can detect hidden blood or DNA changes associated with colorectal cancer. Depending on the specific test, they are repeated every one to three years. If the results are abnormal, a follow-up colonoscopy is required.
Despite these options, many people avoid screening because colonoscopies require bowel preparation, sedation, time away from work, and many patients simply dread the procedure. As colorectal surgeon Dr. Ketan Thanki explained, “Colonoscopies are expensive and time-consuming, and people often dread the prep and have a fear of complications. Blood and stool tests avoid those issues.”
A Simple Blood Test Joins the List
The new screening option is the Shield blood test, which was approved by the FDA in 2024 and has now been added to the American Cancer Society’s screening guidelines for average-risk adults who decline or do not complete preferred screening methods. The test is recommended every three years.
The test works by analyzing a small blood sample for DNA changes released by colorectal cancer cells into the bloodstream. Instead of collecting a stool sample or undergoing an invasive examination, patients simply have blood drawn during a routine medical visit.
For many people, that convenience could make the difference between getting screened and continuing to postpone testing.
As Dr. Lilian Chen noted, “The best screening test is ultimately the one that gets done consistently.”
The Advantages and Limitations
The blood test offers several important advantages. It is quick, minimally invasive, requires no bowel preparation, no sedation, and no recovery time. It may also improve access for people living in rural or underserved areas where colonoscopy services are less readily available.
However, the blood test does have important limitations.
Unlike a colonoscopy, it cannot remove polyps or identify exactly where abnormalities are located. More importantly, blood tests are less effective at detecting advanced precancerous lesions and some stage 1 cancers. Because of this, they may miss cancers at their earliest and most treatable stages.
Dr. Thanki remains clear about the preferred order of screening choices. “It remains the gold standard because colonoscopies are very good at detecting abnormal lesions, identifying exactly what those lesions are, and most importantly, are preventative.” He added that blood tests “would be my last choice as they are generally best at detecting later-stage cancers and can miss precancerous polyps and early-stage cancers.”
Another important point is that any positive blood test must still be followed by a colonoscopy within six months. The blood test is a screening tool, not a definitive diagnostic procedure.
An Easier First Step
Experts increasingly view the blood test as a practical way to reach people who have avoided screening altogether.
Dr. Biachi described it as an “entry-level option” for patients who have been putting off testing. While he still recommends colonoscopy every ten years for most healthy adults beginning at age 45, he recognizes that convenience matters. Ultimately, he said, “the right choice depends on your personality, lifestyle, and how much you value convenience versus maximum effectiveness.”
The American Cancer Society hopes that offering another screening option will encourage millions of Americans to take action. For people who have delayed a colonoscopy because of fear, inconvenience, or lack of time, a simple blood draw may finally provide the motivation to get screened. While it does not replace the effectiveness of a colonoscopy, it is far better than skipping screening altogether, and early detection remains the single best defense against one of America’s most preventable cancers