"It was just fatigue." This is how a 52-year-old man described the first signs that he ignored for months. A teacher, active and with no known history of cancer, he believed that the change in bowel function was a consequence of the stress of his routine. He had no severe pain, saw no obvious blood in his stool, and continued working normally.

During a routine consultation at the Basic Health Unit, the physician suggested a simple test: the FIT, an acronym for Fecal Immunochemical Test. The result came back positive. After the colonoscopy, an advanced polyp was discovered in the intestine—a lesion that could evolve into cancer in the coming years. The problem was removed before that could happen.

Cases like this help explain why FIT has been gaining ground in colorectal cancer screening strategies in the Brazilian public health system (SUS) and in various countries.

What is FIT?

FIT (Fecal Immunochemical Test) is an exam that detects small amounts of occult blood in stool, invisible to the naked eye. Unlike older occult blood tests, it uses specific antibodies to identify human blood from the large intestine.

In practice, the patient collects a small stool sample at home and sends it for laboratory analysis.

The main objective is to identify early signs of intestinal changes even before symptoms appear.

Does FIT detect only cancer?

No.

Although it is best known for helping in early detection of colorectal cancer, the test can also identify other alterations that cause intestinal bleeding, such as:

  • intestinal polyps;

  • adenomas (precancerous lesions);

  • diverticulosis;

  • inflammatory bowel disease;

  • hemorrhoids;

  • anal fissures;

  • colitis.

Therefore, a positive FIT does not necessarily mean cancer. It only indicates that there is intestinal bleeding that needs to be investigated.

Which cancer does the test help detect?

The main focus is colorectal cancer, which affects:

  • colon;

  • rectum;

  • end portion of the large intestine.

This is one of the cancers that has been growing most rapidly in Brazil and worldwide.

According to the National Cancer Institute (INCA), Brazil is expected to register approximately 45,630 new cases of colorectal cancer per year in the current three-year period, with approximately 21,970 cases in men and 23,660 in women.

Colorectal cancer is already among the most frequent in the country, especially in the South and Southeast regions.

Who should have FIT done?

The test is most indicated for asymptomatic people with usual risk, mainly starting from ages 45 to 50, depending on the screening strategy adopted by the health service.

Both men and women can undergo the test.

In general:

People without symptoms and without risk factors

  • screening usually begins between ages 45 and 50;

  • FIT can be performed periodically, usually annually or biennially, according to adopted protocol.

People with symptoms

Even below the screening age, the test can be requested when there are:

  • blood in stool;

  • persistent change in bowel habits;

  • unexplained weight loss;

  • anemia;

  • persistent abdominal pain;

  • sensation of incomplete evacuation;

  • significant family history.

In these cases, colonoscopy often ends up being necessary regardless of the FIT result.

Does FIT replace colonoscopy?

Not completely.

FIT is considered a screening and surveillance test. It helps select patients who need more in-depth investigation.

When the result is positive, the next step is usually colonoscopy.

The main advantage of FIT is that it is:

  • simple;

  • noninvasive;

  • painless;

  • less expensive;

  • accessible;

  • easy to repeat periodically.

Colonoscopy, on the other hand, remains the most comprehensive test because it allows direct visualization of the intestine and polyp removal during the procedure.

What are the risk factors for intestinal cancer?

The main factors associated with colorectal cancer include:

  • age over 50 years;

  • obesity;

  • sedentary lifestyle;

  • smoking;

  • frequent alcohol consumption;

  • diet rich in processed meats;

  • low fiber intake;

  • family history;

  • inflammatory bowel diseases.

The increase in sedentary lifestyle, obesity, and ultraprocessed food consumption concerns specialists because it has been raising the incidence of this cancer in younger adults.

What symptoms warrant attention?

Intestinal cancer can remain silent for years.

When symptoms do appear, the most common include:

  • blood in stool;

  • persistent diarrhea or constipation;

  • change in stool shape;

  • abdominal pain;

  • anemia;

  • unexplained weight loss;

  • frequent fatigue;

  • sensation of incomplete evacuation.

The problem is that many patients only seek help when the disease is already in more advanced stages.

Why is early detection so important?

When identified early, colorectal cancer has high chances of cure.

Moreover, many cases can be prevented before cancer even appears, through the removal of intestinal polyps identified on exams.

Specialists also warn that late diagnosis significantly increases treatment costs for the SUS and reduces the chances of therapeutic success.

Does the SUS offer the test?

Access may vary depending on the region, local availability, and screening programs implemented by municipalities and states.

In recent years, FIT has received greater attention precisely because it has good capacity for population screening with lower cost than universal colonoscopy strategies.

The trend is for the test to be increasingly incorporated into colorectal cancer prevention public policies.

What can be done to reduce risk?

Some measures help in prevention:

  • maintain a diet rich in fiber;

  • consume fruits, vegetables, and legumes;

  • reduce processed meats;

  • exercise regularly;

  • control weight;

  • avoid smoking;

  • reduce alcohol;

  • undergo preventive screenings at the recommended age.

When to see a doctor?

Any persistent intestinal change deserves medical evaluation, especially after age 45.

Even people without symptoms may need to begin preventive screening depending on age and family history.

Early diagnosis remains one of the most important tools for reducing deaths from intestinal cancer.

This content is exclusively informational in nature and does not replace medical consultation, individualized evaluation, or specialized professional follow-up. In case of symptoms or doubts, seek health care.

Dr. Rebeca Soares Andrade CRM-GO 39335