Colorectal Cancer Detection
What are the symptoms of colorectal cancer?
The symptoms of colorectal cancer are very non specific, actually. It can be anything from a vague abdominal discomfort or pain that doesn't go away to change in bowel habits: diarrhea, constipation, something again which doesn't go away after a couple days, that it persists. There can be a loss of weight, that can be a sign of colorectal cancer. Or bleeding, blood in the bowel movements. Feelings of fatigue or symptoms of anemia: shortness of breath, difficulty climbing stairs, carrying things can be the earliest signs of colorectal cancer because the chronic blood loss from polyps and from colorectal cancer can lead to an anemia. And often times, it's the anemia symptoms which call somebody to medical attention.
What is an "anal pap smear"?
An anal pap smear is a test that looks for atypical cells in the anus. The anal pap smear does not screen for colon cancer. The anal pap smear does not screen for rectal cancer. The anal pap smear is a screen for anal cancer. Because just like cervical cancer, the earliest signs of atypical cells can indicate that a cancer may present later down the line. And it's not clear exactly what to do if you find atypical cells. For a pap smear, we know that doing surgical procedures, cryotherapy, whatnot can help to prevent a cervical cancer from occurring. For anal pap smears, we just don't have the long term studies to show that cryotherapy to these atypical cells can prevent an anal cancer later on, but the anal pap smear is a test for certain individuals who may be at higher risk for developing anal cancer. In other words, people with a history of anal warts, or people who engage in anal-receptive intercourse are at higher risk for developing anal cancer, and should have an anal pap smear.
What is "cryotherapy"?
Cryotherapy is a procedure that uses cold substances to destroy surface cells while keeping the cells underneath - the healthy cells - alive and well. The purpose of cryotherapy is to try to kill the atypical precancerous cells before they ever have the chance of developing into cancer.
What is "anal cancer"?
Anal cancer is cancer of the anus, which is the tissue between the rectum and the outside of the body that expels waste from the gastrointestinal tract. The anus is lined with squamous epithelium which is different to the cells that line the inside of the colon and the rectum. Therefore, the type of cancer that happens to the anus is different than the type of cancer that happens to the colon or the rectum.
What is an "enema" and "barium enema"?
An enema is the process of infusing liquid into the rectum. An enema is done by inserting a tube into the anus and then using gravity to pull liquids into the rectum and the colon. It can be used to help somebody to have a bowel movement if they're constipated. Specifically for cancer, a Barium enema is a test where Barium is put into the bowel and then X-rays are taken. Barium is a radio opaque material, meaning that it shows up as a white area on an X-ray following the enema. Based upon where Barium shows up and where it doesn't, we can examine the lining of the colon and the lining of the intestine to see if there are any areas that are concerning for polyps or colorectal cancer.
Is barium a safe substance?
Overall, Barium is a safe substance. One of the main side effects is that it can potentially cause constipation, but usually that does not happen when it's instilled as an enema. If people drink Barium to get X-Rays of the upper intestinal tract it is less safe, as it can take some time to pass through the intestine and cause constipation in those instances Usually this does not occur when it's used in a Barium enema.
What is a "colonoscopy"?
A colonoscopy is a test that is done by a physician, usually a gastro-enterologist or surgeon who inserts a scope which has a small camera and a small light on the end of it into the rectum and up through the colon. You can see the sides of the colon to evaluate for any abnormalities, polyps, early cancers or any full cancers which then, through the small hole in the scope can be biopsied and the tissue can be analyzed by the pathologist to see if it is indeed cancer or a benign polyp. For a colonoscopy, before somebody is ready to undergo one, it's important that they have an appropriate bowel preparative regimen. That means that they drink liquids that are laxatives that cause them to go to the bathroom so that their intestine, in particular their colon, becomes clean.
What is a "flexible sigmoidoscopy" or "flex-sig"?
A flex sig or a flexible sigmoidoscopy is where a smaller tube rather than the full colonospic tube is used to evaluate the rectum and just the sigmoid colon. The flex sig does not go higher up into the colon to evaluate everywhere for polyps; the flex sig just evaluates the last third of the colon for any abnormalities. Meaning, polyps, sources of bleeding, or cancers.
What is a "virtual colonoscopy"?
A virtual colonoscopy is a new technology that utilizes CT scanning, which is non-invasive imaging, to look inside the colon for any abnormalities in the wall of the colon; in other words, polyps, pre-cancers, or cancers. The good thing about a virtual colonoscopy is that people don't need to be sedated. They just go into a CT scanning machine, and the virtual colonoscopy is a relatively quick, painless test. The downside is that, if there's any abnormalities that are seen on the virtual colonoscopy, they still need to undergo a colonoscopy to go in and get a biopsy so that we can tell if it's cancer, if it's not cancer, if it's a polyp, so it can be removed and be prevented from ever becoming cancer.
What is a "digital rectal examination"?
A digital rectal exam is where a clinician inserts his or her finger into the anus, to feel the mucosa of the anus, as well as the rectum, to feel if there are any abnormalities that feel like a polyp or a cancer which could indicate that a biopsy is needed. It's important for men because we need to be able to check the prostate to make sure there are no abnormalities of the prostrate, and we can also check the anus and the most distal part of the rectum at that time. It can be helpful for women too; to check the mucosa as well as to check for any pelvic or gynaecologic abnormalities.
What is a "DNA stool test"?
A DNA stool test is a new test that is in clinical trials right now. It is not something that is recommended for the average person to get. It's a test that evaluates the stool for any cells that have DNA damage consistent with having colorectal cancer or having an atypical adenoma or a lesion which are concerning for developing into colorectal cancer later. The difficult thing is that it is just right now in clinical trials; it's a new technology and we don't know how best to incorporate it into clinical practice, so it is something that is on the horizon but it is not something right now that is recommended for individual to have outside of a clinical trial.
What is a "CBC"?
CBC stands for a complete blood count, and it's basically just a blood test that evaluates somebody's white blood cell count, their red blood cell count, and their platelet count. As far as it's related to colorectal cancer, the important thing is the red blood cell count; seeing if somebody is anaemic, and seeing if those red blood cells are consistent with iron deficiency anaemia. Iron deficiency anaemia can be associated with colorectal cancer because it is the chronic blood loss or the chronic iron loss which happens through shedding from the colorectal cancer, which then can lead to somebody developing anaemia and developing symptoms of anaemia, which then leads them to seek medical attention.
How are "liver function tests" used to detect colorectal cancer?
Liver function tests are blood tests that evaluate certain proteins that are made in the liver. Liver function tests are not good for detecting colorectal cancer because if there are abnormalities in these tests, it's usually because the cancer has already spread to the liver. This means you're picking up the colorectal cancer at a much later stage. Thus, they're not useful for screening for colorectal cancer.
What are "tumor markers"?
Tumour markers - CEAs or Carcino Embryonic Antigens - are proteins that are sometimes made by colorectal cancer. Not all colorectal cancers make tumour markers, and these proteins can also be elevated in other types of cancers, so they are very non-specific. In addition, some individuals can have an elevated CEA and not have cancer at all. Therefore, the usefulness of CEA tests is not in detecting cancer but in following individuals with cancer. With Individuals who have metastatic colorectal cancer that makes CEA, we can follow CEA as a marker for their response to therapy. In other words, generally if somebody is responding to therapy, the CEA comes down and if they're not responding to therapy, the CEA goes up.
What is a "FOBT"?
An "FOBT", or a "Fecal Occult Blood Test", is a test to see if there's any blood in the stool. Occult blood is blood that you cannot see: it's there, but we're not sure it's there until we run an FOBT. The reason Fecal Occult Blood Tests are important is because polyps and cancers can bleed. So, on a FOBT, if there is blood present it may indicate that somebody has a polyp or colorectal cancer that we need to find, and it can prompt a colonoscopy.
What is a "FIT"?
A fecal immunochemical test, or an FIT, is a newer type of fecal occult blood test. The traditional fecal occult blood test just looks to see if there is blood in the bowel movement. It doesn't tell us where that blood came from and there can be false positives and false negatives. If somebody has eaten a diet high in iron, or steak, or animal flesh, that can sometimes show up as a false positive on a fecal occult blood test. In addition, if somebody is on aspirin or anti-inflammatories which can irritate the stomach, and if there's any type of blood that oozes from the stomach, this can be picked up on a fecal occult blood test. But the FIT, the fecal immunochemical test, is basically just looking for undigested human hemoglobin. It won't pick up any animal hemoglobin and it won't pick up digested blood from higher up in the intestinal tract. So it is more specific for bleeding in the colon or in the rectum and therefore more useful for separating out blood that is present from a potential polyp or colorectal cancer.
