Colorectal Cancer (also named Colon Cancer or Rectal Cancer, depending on where they start, but often grouped together because they have many features in common), is a cancer that starts in the colon or the rectum. These both parts form the large intestine ―or large bowel―. Most of the large intestine is made up of the colon, a muscular tube about 5 feet long, that absorbs water and salt from the remaining food matter after it goes through the small intestine (small bowel). The waste matter that is left after going through the colon goes into the rectum ―the final 6 inches of the digestive system―, where it is stored until it passes out of the body through the anus.
Most Colorectal Cancers begin as a growth on the inner lining of the colon or rectum called a polyp. Some types of polyps can change into cancer over the course of several years, but not all polyps become cancer. The chance of changing into a cancer depends on the kind of polyp.
The 2 main types of polyps are:
- Adenomatous polyps (adenomas): polyps that sometimes change into cancer (because of this, adenomas are called a pre-cancerous condition).
- Hyperplastic polyps and inflammatory polyps: polyps that are more common, but in general they are not pre-cancerous.
Dysplasia, another pre-cancerous condition, is an area in a polyp or in the lining of the colon or rectum where the cells look abnormal (but not like true cancer cells).
Types of Colorectal Cancer
The 95% of Colorectal Cancers start in cells that form glands that make mucus to lubricate the inside of the colon and rectum. When doctors talk about Colorectal Cancer, they are almost always talking about this type:
- Adenocarcinomas: type of cancer that make up more than 95% of colorectal cancers. These cancers start in cells that form glands that make mucus to lubricate the inside of the colon and rectum.
By other way, other less common types of tumors can also start in the colon and rectum, such as:
- Carcinoid Tumors: type of cancer that starts from specialized hormone-making cells in the intestine.
- Gastrointestinal Stromal Tumors (GISTs): type of tumors that starts from specialized cells in the wall of the colon called the interstitial cells of Cajal and that in some cases are non-cancerous (benign). These tumors can be found anywhere in the digestive tract, but it is unusual to find them in the colon.
- Lymphomas: type of cancer of immune system cells that typically start in lymph nodes, but they can also start in the colon, rectum, or other organs.
- Sarcomas: type of cancer that can start in blood vessels, muscle layers, or other connective tissues in the wall of the colon and rectum. By the way, sarcomas of the colon or rectum are rare.
Researchers have found several risk factors that might increase a person’s chance of developing Colorectal Polyps or Colorectal Cancer, being the most relevant:
- Being older
- A personal history of Colorectal Polyps or Colorectal Cancer
- A personal history of Inflammatory Bowel Disease (IBD)
- A family history of Colorectal Cancer or Adenomatous Polyps
- Having an inherited síndrome
- Your racial and ethnic background
- Having type 2 diabetes
Besides, links between diet, weight, and exercise and Colorectal Cancer risk have been also detected. Most lifestyle-related factors linked to Colorectal Cancer are:
- Being overweight or obese
- Physical inactivity
- Certain types of diets
- Heavy alcohol use
Signs and Symptoms
Colorectal Cancer might not cause symptoms right away, but if it does, most of them are more often caused by conditions other than Colorectal Cancer, such as infection, hemorrhoids, or irritable bowel syndrome.
Some of possible symptoms and signs may include:
- A change in bowel habits, such as diarrhea, constipation, or narrowing of the stool, that lasts for more than a few days
- A feeling that you need to have a bowel movement that is not relieved by doing so
- Rectal bleeding
- Blood in the stool, which may make it look dark
- Cramping or abdominal (belly) pain
- Weakness and fatigue
- Unintended weight loss
Besides, Colorectal Cancers can often bleed into the digestive tract. While sometimes the blood can be seen in the stool or make it look darker, often the stool looks normal. But over time, the blood loss can build up and can lead to low red blood cell counts (anemia). Sometimes the first sign of Colorectal Cancer is a blood test showing a low red blood cell count.
The survival rate in colorectal cancer is related to the stage the tumour is and its localization. Tumours that develops in the rectus, are more prone to be more lethal than those grown in the colon. In addition, the main difference can be noticed between initial and advanced stages. The 5-year relative survival rate for people with stage I of colorectal cancer is about 90%., being between 80% and 50% in stage II depending if it is IIA or IIB respectively. The same happens in stage III, where the 5-year relative survival rate for stage IIIA is about 80% and 50% in stage IIIB. Colon cancers that have spread to other parts of the body are often harder to treat and tend to have a poorer outlook. Metastatic, or stage IV colon cancers, have a 5-year relative survival rate of about 11%. Still, there are often many treatment options available for people with this stage of cancer.
Colorectal Cancer Diagnosis
PLEASE NOTE: EARLY DIAGNOSIS IN CANCER IS VERY IMPORTANT BECAUSE CANCER THAT’S DIAGNOSED AT AN EARLY STAGE ―BEFORE IT’S HAD THE CHANCE TO GET TOO BIG OR SPREAD―, IS MORE LIKELY TO BE TREATED SUCCESSFULLY. IF THE CANCER HAS SPREAD, TREATMENT BECOMES MORE DIFFICULT, AND GENERALLY A PERSON’S CHANCES OF SURVIVING ARE MUCH LOWER.
State of the Art
Some techniques have been developed with the aim of diagnosing colorectal cancer. The used are colonoscopy and blood tests; but these present some limitations as it could be the stress on the patient caused by the insertion of the tube or the lack of specificity of the blood test. For these reasons, it is necessary to develop new methods in order to tackle the identification of this kind of cancer.