Introduction: Who Should Undergo Diagnostics

Metastatic colorectal cancer means that cancer which started in the colon or rectum has traveled to other parts of the body. This is also called stage 4 or advanced colorectal cancer. Even though the cancer has spread, it can still be managed with proper treatment and monitoring.^[1]

People who should consider diagnostic testing include those who already have been treated for colorectal cancer and are being monitored for signs that the disease has returned. Cancer can come back months or even years after the original treatment, so regular follow-up tests are important. If the original cancer was removed before it had a chance to spread, the chances of it returning are lower, but monitoring is still essential.^[3]

It’s also important to seek diagnostic testing if you develop new symptoms that might suggest cancer has spread or returned. These symptoms can include changes in bowel habits such as diarrhea or constipation that lasts for weeks, blood in the stool which appears as bright red blood or stools that look like black tar, unexplained weight loss, constant tiredness that doesn’t improve with rest, or pain in the belly that feels like cramps, gas, or a feeling of fullness.^[6]

If colorectal cancer has already been diagnosed and there’s concern it might have spread, additional symptoms may appear depending on where the cancer has traveled. For example, if cancer spreads to the liver, symptoms might include pain in the upper right part of the abdomen, yellowing of the skin and eyes known as jaundice, or swelling in the belly area. When cancer reaches the lungs, it can cause shortness of breath, persistent coughing, or chest pain. Spread to the brain might lead to headaches, seizures, dizziness, or confusion.^[1][3]

Some people with metastatic colorectal cancer may not experience any symptoms for quite some time. This is why doctors recommend regular monitoring and screening tests even when you feel well. Early detection of cancer spread can make a significant difference in treatment options and outcomes.^[6]

Diagnostic Methods for Identifying Metastatic Colorectal Cancer

Diagnosing metastatic or recurrent colorectal cancer involves using a combination of different tests. Doctors need to confirm whether cancer is present, determine where it has spread, and understand its characteristics to plan the best treatment approach. The process typically includes physical examinations, imaging tests, laboratory work, and tissue sampling.^[3]

Physical Examination

A physical exam is often one of the first steps in diagnosis. During this exam, your doctor will check for physical signs of cancer, such as lumps, swelling, or tenderness in the abdomen. They may also perform a digital rectal exam, where they use a gloved finger to feel inside the rectum for any abnormalities. While this exam can feel uncomfortable, it provides important information about the lower digestive tract.^[8]

Colonoscopy

A colonoscopy allows doctors to see inside your intestine and check if cancer has returned to the bowel. During this procedure, a thin, flexible tube with a camera on the end is inserted through the anus and guided through the large intestine. The doctor can view the lining of the colon on a screen and look for suspicious areas. If any abnormal tissue is found, small samples can be taken right away for further testing.^[6]

Colonoscopy is particularly helpful because it provides direct visualization of the inside of the colon and rectum. This makes it possible to see changes in the tissue that might not show up on other types of tests. Patients are typically given sedation to make them more comfortable during the procedure.^[6]

Imaging Tests

Imaging tests create pictures of the inside of your body and are essential for finding out if cancer has spread to other organs. Several different types of imaging may be used, and each provides different information about the cancer.

CT scans, also called computed tomography scans or CAT scans, use X-rays taken from many angles to create detailed cross-sectional images of the body. CT scans are the main imaging tests used to detect colorectal cancer and determine how far it has spread. They can show tumors in the chest, abdomen, and pelvis, helping doctors see if cancer has reached organs like the liver, lungs, or lymph nodes.^[8][6]

MRI scans, or magnetic resonance imaging, use powerful magnets and radio waves instead of X-rays to create detailed images of soft tissues. Like CT scans, MRI can help doctors see if colorectal cancer has spread to organs in the belly or pelvis. MRI may also be used to get a clearer picture of the brain if there are symptoms suggesting the cancer has spread there.^[6][8]

PET scans, which stands for positron emission tomography, involve injecting a small amount of radioactive sugar into the bloodstream. Cancer cells absorb more of this sugar than normal cells, causing them to light up on the scan. PET scans can help doctors decide if surgery is an option for cancer that has spread outside the colon, as they can show how active the cancer cells are in different parts of the body.^[8][6]

Doctors may also use ultrasound to examine organs like the liver. Ultrasound uses sound waves to create pictures of the inside of the body. It’s painless and doesn’t involve radiation. A bone scan might be ordered if there’s concern that cancer has spread to the bones. This test uses a small amount of radioactive material that collects in areas where bone is breaking down or repairing itself, which can happen when cancer affects the bones.^[6]

Blood Tests

Blood tests can provide important clues about whether cancer is present or progressing. One commonly used test is the carcinoembryonic antigen test, often called CEA. This test measures the level of a protein that some colon cancer cells produce. High levels of CEA in the blood can indicate the presence or progression of colon cancer, especially in advanced stages. However, CEA levels alone cannot diagnose cancer because other conditions can also raise these levels.^[8][6]

Blood tests may also check for anemia, which is a low red blood cell count. Colorectal cancer can cause bleeding in the digestive tract that leads to anemia. Signs of anemia include feeling tired, weak, and having pale skin. Other blood tests evaluate overall health and organ function, which helps doctors understand if the liver, kidneys, or other organs are affected by the cancer.^[1]

Biopsy

A biopsy is the removal of a small sample of tissue for examination under a microscope. It’s usually the only way to definitively confirm that cancer is present and determine what type it is. For colorectal cancer, the tissue sample is often collected during a colonoscopy. Sometimes surgery is needed to obtain the tissue sample, particularly if the suspicious area is in a location that’s hard to reach.^[8]

If imaging tests show a suspicious mass in the liver or lung, a doctor might perform a liver biopsy or lung biopsy to remove a small piece of tissue from that organ. This helps confirm whether the mass is cancer that has spread from the colon or rectum.^[6]

Once the tissue sample reaches the laboratory, tests can show whether the cells are cancerous, what type of cancer it is, and how aggressive it appears. Additional tests on the cancer cells provide information about genetic changes present in those cells. Understanding these genetic features helps doctors predict how the cancer will behave and which treatments are most likely to work.^[8]

Molecular and Genetic Testing

Some colorectal cancers have specific gene changes that affect how the cancer grows and responds to treatment. These genetic features are identified by testing the cancer tissue in a laboratory. Such tests are increasingly important because certain medications only work for cancers with specific gene changes. Doctors use this information to select the most effective treatment for each individual patient.^[8]

Testing may look for mutations in genes or changes in proteins that influence how cancer cells grow and spread. This detailed analysis, sometimes called biomarker testing, informs which targeted therapies or immunotherapies might be most helpful. It’s become standard practice to perform these tests on tumor samples from patients with metastatic colorectal cancer.^[7]

Diagnostics for Clinical Trial Qualification

Clinical trials are research studies that test new treatments or new combinations of existing treatments. They can offer access to cutting-edge therapies that aren’t yet widely available. For patients with metastatic colorectal cancer, participating in a clinical trial may be an important option, especially if standard treatments haven’t worked well or have caused too many side effects.^[3]

To qualify for a clinical trial, patients typically need to undergo specific diagnostic tests. These tests ensure that participants meet the criteria for the study and that the treatment being tested is appropriate for their particular type and stage of cancer. The exact tests required vary depending on the specific trial, but there are some common diagnostic procedures used to determine eligibility.^[3]

Confirming Cancer Type and Stage

Clinical trials usually require confirmation that a patient has metastatic colorectal cancer and documentation of where the cancer has spread. This means having recent imaging tests such as CT scans, MRI, or PET scans to show the location and extent of cancer in the body. Trials often specify how recently these images must have been taken, such as within the past few weeks or months.^[8]

Tissue samples from biopsies must typically be available to confirm the cancer diagnosis. Some trials require fresh tissue samples, while others can work with samples collected during earlier procedures. The cancer tissue is analyzed to verify that it is indeed colorectal cancer and not a different type of cancer that spread to the colon or rectum.^[8]

Biomarker and Genetic Testing

Many clinical trials for metastatic colorectal cancer focus on treatments that target specific genetic mutations or biomarkers. Therefore, detailed molecular and genetic testing of the tumor is often required for enrollment. Researchers need to know if the cancer has certain gene changes, such as mutations in specific genes or alterations in proteins that affect cell growth.^[7]

For instance, some trials test treatments that work only for cancers with certain characteristics, while others specifically look for patients whose cancers don’t have particular mutations. Biomarker testing helps match patients with the clinical trials where they’re most likely to benefit from the experimental treatment. This personalized approach to medicine aims to improve outcomes by selecting treatments based on the unique features of each person’s cancer.^[7]

Blood Tests and Overall Health Assessment

Clinical trials typically require baseline blood tests to assess a patient’s overall health and organ function. These tests check how well the liver, kidneys, and bone marrow are working. Good organ function is often necessary to safely tolerate new treatments being tested. Blood tests might also measure specific markers like CEA levels to establish a starting point for tracking how the cancer responds to treatment during the trial.^[8]

Additional health assessments may include measurements of heart function through tests like electrocardiograms, especially if the experimental treatment might affect the heart. Researchers need to ensure that participants are healthy enough to receive the treatment and to distinguish treatment effects from pre-existing health conditions.^[8]

Imaging Tests for Trial Monitoring

Beyond the initial diagnostic tests for enrollment, clinical trials often involve regular imaging tests throughout the study period. These ongoing scans help researchers track how well the experimental treatment is working. They provide objective measurements of tumor size and can show whether cancer is shrinking, staying the same, or growing despite treatment. This information is crucial for determining whether the new treatment being tested is effective.^[8]

The frequency of these follow-up imaging tests depends on the trial protocol. Some studies require scans every few weeks, while others space them out over months. Participants need to be willing and able to undergo these repeated tests as part of their commitment to the clinical trial.^[8]

Documentation and Medical History

Clinical trials require detailed documentation of a patient’s medical history, including all previous cancer treatments. This means having records of past surgeries, chemotherapy regimens, radiation therapy, and any other treatments received. Researchers need to understand what treatments have already been tried and how the cancer responded to them. This information helps determine if a patient is suitable for a trial and provides context for interpreting the results of the experimental treatment.^[3]

Having organized medical records that include dates of diagnosis, treatment details, imaging reports, pathology results, and documentation of disease progression makes the enrollment process smoother. Your healthcare team can help gather these records if you decide to explore clinical trial options.^[3]