Other tests for colorectal cancer — If the doctor is unsure about the presence of the cancer, he may advise backup tests that will definitively confirm cancer. We’ve listed the most common tests for colorectal cancer here:
Colonoscopy — Colonoscopy refers to the process of visually examining the colon and rectum with a thin, flexible tube. The tube contains a camera, a light source, and a thin filament that carries information to the attached computer. The tube is inserted in the colon through the anus and pictures are transmitted back to the operating computer. A doctor will view the images and confirm/ deny the presence of cancer. For small cancers, benign lumps or polyps, incising instruments can be passed through the same tube and treatment can be done at the same time. Colonoscopy is usually done in the outpatient department of the hospital, in a clinic or at a clinic.
Preparing for the test — If you have been advised a colonoscopy, you can prepare for the test by following instructions given by the doctor. Tell the doctor about any medications that you are taking. The colon and rectum also have to be empty before the test can be done. As a result, you may be asked to take a liquid laxative to clean out your intestine before the test. This means you will be spending most of the previous evening and night in the bathroom emptying your colon and rectum. You will be given clear instructions on how to consume medication and water to make the test easier. Make sure you buy everything in advance. If you are not understanding the medical instructions, you will have to call the doctor’s office and review the instructions with the nurse.
Food consumption before the test – Bowel preparation is difficult, but it is vital to the success of the colonoscopy. You may also have to consume only clear liquids like water, apple juice, tea, white grape juice or clear jelly to ensure a clean bowel. Please note that tea and coffee are fine, but milk and creamer are not allowed. Avoid all foods that are highly colored as they tend to color stool and this makes the viewing process difficult. You can consume clear soup, ginger ale, clear sports drinks, and most soft drinks to ensure an accurate test. You will have to avoid all food the night before the test. If you consume medications, discuss how you will be taking them before the test.
During the test — A mild sedative is given to relax the patient. The test usually takes 30 minutes or less. Before the process, you may also be given an IV sedative to make your sleepy and comfortable. You will be awake, but you won’t remember the process afterward. During the examination, the doctor will insert a gloved finger into the rectum to assess it before a colonoscope is inserted. You will be asked to lie on your side with your knees pulled up towards your chest. A drape will cover you completely. An anesthetist will measure your temperature, BP, and pulse during the entire process. The colonoscope is lubricated and then inserted in the rectum through the anus. The anus is very constricted. Sometimes visualization of the colon interior is very difficult. In this case, the operator injects a neutral gas into the colon and inflates it gently. This makes it easier to see the color and visualize problem areas.
Treatment — During the visualization process, the doctor may sometimes find small polyps or problem areas. In this case, treatment can be immediate. A wire loop present in the colonoscope is heated and used to scrape off the polyp and a little of the surrounding area. An electric current is passed through the loop, and it acts like an electric cautery. The cauterized tissue is then sent to the lab to evaluate it for medical problems. This process is called a biopsy, and it is quite simple. The cut tissue is stained or colored with special dyes and then checked under a microscope for abnormal growths.
Possible effects of the procedure — The colonoscopy is uncomfortable, and patients may experience pain and discomfort after the process. However, the sedative usually helps the patient deal with the discomfort and pain. During the process, the intestine is pumped up with air, and this can result in a bloated feeling with cramps and pains. However, once the extra gas is passed through the anus, the pain and discomfort wears off. Very rarely patients experience irregular heartbeats and low blood pressure. However, as there is a doctor monitoring the process and the patient’s vital signs, these side effects are managed quite well.
After the test – Most people are fully awake by the time the test is complete, and they are physically able to go home. We do recommend that you arrange someone to take you home. In case a poly was removed, or if treatment was done, you might notice blood in your stool. In very rare cases, serious bleeding may take place but this is usually manageable. A colonoscopy procedure is quite simple and very safe. However, very rare complications include a bowel perforation. When this happens, the patient may experience severe cramping pain, belly aches, nausea, vomiting, and other symptoms. This can be life threatening, and it requires immediate medical intervention.
Biopsy — Biopsies are an important test done to assess the type and extent of spread of the cancer. In a biopsy, the doctor will take a sample of the indicated tissue. Sometimes, the doctor will excise the entire tissue and then send it to the laboratory for viewing. In the lab, the tissue is stained and prepared for viewing under the microscope. By doing this, the lab technician can assess the type of tissue growth and how far it could have spread in the body. After a biopsy, some patients may experience pain and bleeding but this usually stops by itself. In some cases, the cancer has spread so much, that the entire rectum, part of the colon, or the entire colon is removed. If this was done the patient may require backup surgeries to create alternative stool openings.
Testing of Tissue Samples — At the lab, the tissue samples are evaluated by a medical professional called a pathologist. The pathologist can detect tissue changes that indicate cancer, and he will classify the type of cancer as well.
Gene Tests may also be done on the tissue samples. Certain cancers have specific genetic markers that are indicative of specific cancers. These genes will also tell the doctor exactly how to treat the cancer. For example, most pathologists and surgeons will test tissue samples for the KRAS gene. In this case, the gene is mutated in about 4 out of 10 patients who have colorectal cancer. A few doctors may also test for other genetic changes like the BRAF gene. This is quite interesting as detecting the gene can influence treatment in colorectal cancer patients. for example, patients with this kind of cancer gene cannot be treated with some anti-cancer drugs like cetuximab (Erbitux®) and panitumumab (Vectibix®).
MSI Testing — This is another unique type of tissue testing that is done to check for a genetic predisposition to cancer. MSI refers to microsatellite instability and colorectal cancers usually do demonstrate this change inside the cell structure. MSI changes are also seen in patients who have colorectal cancer caused by HNPCC or hereditary non-polyposis colon cancer. However, it may also be seen in patients who do not have this type of colorectal cancer. In this case, you may be wondering why the MSI test is done. The test is done to find patients who already have HNPCC. If the patient is confirmed with HNPCC, then treatment can be started, and preventive screening can be done to catch any signs of colorectal cancer. It may also be advisable to screen the entire family for HNPCC to assess the familial risk for developing cancer. A few patients may be asked to do MSI testing only if required. The doctor may also assess each patient for suitability and risk for cancer before doing the test. Another way to do it is by starting with an immunohistochemistry test. If this test comes positive, then the patient may be tested further with an MSI test. Not all patients who have been tested for cancer will show positive MSI and HNPCC results.
Imaging tests — Apart from colonoscopy and biopsy tests, imaging tests are also done to provide a visual idea of the cancer and how far it has spread. However, as colorectal cancer is a soft tissue cancer, it is not visible on ordinary X-rays. In this case, a combination of sound waves, magnetic fields, radioactive substances, and x-rays is used to produce a detailed image of the cancer. The most common imaging tests used to check for soft tissue cancer are listed here:
Computed tomography (CT or CAT) scan — This scanning procedure is one of the most detailed visualization procedures available for doctors. This process produces incredibly detailed cross-sectional images of the body. The images appear like body slices, and the width and depth of the slices can be modified according to requirement. The patient lies down on a table, and the CT scanner moves around the patient to create detailed images of the required body part. The test can tell you if the cancer has spread into different parts of the body. The procedure itself is quite simple and takes less than 20 minutes to complete. In some cases, you may be asked to drink two to three liters of a special liquid called contrast medium. This contrast medium coats your intestine and provides extra detail during scanning. Sometimes, the doctor may provide an IV solution. The contrast medium or dye is injected into the blood, and this also produces a very detailed images. In some cases, the contrast material or dye may produce adverse effects like flushing, redness, feeling of warmth and fullness. These effects subside once the contrast medium is flushed out of the body. In other cases, patients may experience other side effects like allergic reactions, hives, rashes, low blood pressure and even difficulty in breathing. Make sure you tell the doctor is you have any allergies, and the doctor will provide the right medication to help you through the reaction. You should know that different procedures take different times to complete. For example, X-rays are simple and take very little time to complete. However, CT scans take longer than X-rays. You may also need to sit down on a table or a chair while the scan is being carried out. During the procedure, the bed or chair is passed through the donut of the CT scanner. Patients do feel a little claustrophobic while passing through the CT donut but the technician, or the attending physician, will help you deal with the issue. Specific tests like CT Portography are designed to scan the portal vein that carried blood to the liver from the intestine. In this test, contrast medium is injected directly into the veins connecting to the liver as it provides a detailed image of colorectal cancer in case it has spread to the liver.
CT-Scan Guided Needle Biopsy — If a cancerous area lies deep inside the body, then it is possible to insert a thin biopsy needle directly into the cancer. The patient is placed on the bed, and continuous images are produced through the CT scanner. The doctor uses the scanner to guide the needle into the cancerous area. With the needle, he can then collect tissue, blood or liquid for a biopsy. As the procedure is done under the CT scanner, it is referred to as a CT-scan guided needle biopsy.
Ultrasounds — Sound waves are passed through the body to record the images of soft tissue. As soft tissue contains different types of chemicals and it is of a different thickness, the sound waves are absorbed differently, and this absorption is recorded by the ultrasound scanner. The test is painless, effective, and fast and images are produced almost instantly. The technician will move a transducer over the patient’s body, and images are transmitted to a computer for viewing. Different types of ultrasound imaging are done like abdominal ultrasound imaging, endorectal imaging, transesophageal imaging and so on. Intraoperative imaging is also done while the patient is being operated on. The transducer is placed on the liver, and it can produce very detailed images of any potential cancer in the liver.
MRI Scans — Magnetic resonance imaging is a wonderfully detailed way of getting tissue images. Radio waves are passed through the body, and the pattern of absorbed waves are recorded by the machine. In some cases, a contrast medium like gadolinium is also used to increase the difference in tissue imaging. MRIs are a little different from CT scans, and they can be a little uncomfortable as well. The test can take up to an hour, and the patient is placed in a narrow tube. The machine also makes a buzzing and clicking sound that can be a little worrying for the patient. You can wear earplugs to cut out the noise. To improve accuracy, some patients use endorectal coils to produce an endorectal MRI.
Chest X-ray — Chest X-rays are an easy and simple way to produce images of the chest and the abdominal area.
PET scans or positron emission tomography — These PET scans are incredibly accurate. In this test, a radioactive sugar called fluorodeoxyglucose is injected in the blood. Cancer cells pull up large amounts of this sugar and images can be produced quickly.
Angiography — Angiography is the process of recording blood flow through blood vessels. Contrast medium is injected into the artery, and then continuous images are taken as the contrast medium flow through the body. If the cancer has spread to the liver, this process will track the extent of the spread and help doctors plan a treatment protocol. The process may be uncomfortable as a small catheter is pushed into a blood vessel and pushed upward to the liver artery. You may be sedated until the procedure is complete. A local anesthetic is usually injected to make the process as painless as possible. Angiography is also done with a CT scanner to make the process simple and easy.