Our colon is the largest part of the digestive system, and it does not only helps the body digest and absorb the nutrients, but also excretes the waste, undigested material through feces. It is further divided into 5 parts, the ascending colon, transverse colon, descending colon, sigmoid colon and rectum. Cancer can develop in any part of the colon, but it commonly appears in the sigmoid-rectal portion.
According to recent statistics by the American Cancer Society and Cancer Research UK, colon cancer is a leading cause of cancer-related deaths in both men and women. At the initial stages, medically known as “carcinoma in situ”, colorectal cancer symptoms are non-existent or minor, but there may be unusual early warning signs.
In the majority of cases, colon cancer symptoms may not develop until the tumor has grown into stage II or beyond. This is the reason why it remains undetected for several months or years, and doctors often recommend regular screening with a colonoscopy to detect the disease at an early stage. Annual screening for colorectal cancer is a part of a health plan in many developed countries, especially in high-risk groups such as those above 50 years of age or with a history of colon cancer in their family, alcohol abuse, and infectious colon disease that may later turn into cancer.
Depending on the stage and severity of the disease, the classical signs and symptoms of colon cancer include;
1) Unexplained Weight Loss
Sudden and unintentional weight loss can be the primary symptom of various types of cancer, including colorectal cancer. Losing 10 pounds or more in 6 months or less without any obvious reason should raise your concern, and in the case of cancer, it may have various explanations.
Cancer cells tend to grow at a faster pace compared to normal body cells and utilize a lot of the body’s energy such as glucose and other nutrients. The immune system also utilizes energy to fight off and eliminate growing tumor cells. These factors cause massive depletion of energy and nutrients meant to nourish other organs, and ultimately results in loss of muscle mass. Another explanation is that cancer cells release toxic substances that kills the immune cells and change the way your body processes the food to make energy.
Furthermore, when a tumor gets large enough, it could obstruct the colon. It also affects a person’s bowel habits and digestion, which contributes to unexplained weight loss.
2) Fatigue and Weakness
It is easy to confuse fatigue with just being tired. Between personal obligations and work, anybody can feel run down at times. It could be fatigue if it doesn’t go away after properly resting. However, fatigue and weakness could also be due to other health conditions like diabetes, cardiac disease, and anemia.
Chronic fatigue in colon cancer can develop as a result of depleting energy sources, loss of muscle mass and internal blood loss from the disease itself. In the absence of nutrients and energy, the body cells shift their metabolism from glucose to ketones and tend to work harder to strive for existence. This creates an acidic environment in the body. Secretion of metabolic waste products and other associated symptoms like alternative bowel habits can add fuel to the fire and increase the feeling of weakness and fatigue.
3) Abdominal Pain and Cramps
The majority of people experience abdominal pain and cramps at some point. Like many other symptoms, it may seem minor as it commonly develops as a result of non-threatening conditions like irritable bowel syndrome and hemorrhoids. However, the pain can raise concerns when it becomes chronic and won’t get better with over the counter drugs.
Depending on the location of cancer, this pain can be localized in specific abdominal part areas as in the flanks, below and above the navel or in the pelvic area. As the disease progresses, the pain would start getting worse, diffuse through the abdomen and may radiate towards other parts of the body. The abdominal cramping in colon cancer is due to irritation of local nerve supply due to the size of the growing tumor.
4) Blood in the Stools
Blood in the stools is one of the most common and characteristic signs of colon cancer. As the tumor grows in size, it tends to put pressure on the surrounding tissues, including the nerves and blood vessels. Damage to these delicate blood vessels results in hemorrhage and bleeding. The blood in the stools is either red and fresh or black and foul-smelling. Red blood indicates that the bleeding point is somewhere near the anus. In the majority of cases, blood will be visible to the naked eye while in some cases it may only be seen under a microscope. The amount of blood in the stool depends on the location, tumor size, and severity of the disease.
If you have dark feces or blood clots in the stools, it can be due to some other gut condition such as stomach or duodenal ulcers. Blood clots indicate a remote position from the anus.
Sometimes, blood clot also forms in colorectal cancer because of the secondary changes in the gut such as bowel obstruction or constipation. These conditions enable the large intestine to hold stools for a long period of time and may lead to dark-brown or cola-colored stools. Therefore, it is important to consult your health care provider to evaluate and diagnose the underlying cause of your bleeding. Your doctor will examine the stool sample under a microscope, perform a fecal occult test and do additional examinations such as colonoscopy to determine the source of the blood.
5) Rectal Bleeding
Bright red blood on the toilet paper is a common symptom of colorectal cancer that indicates that the blood is coming from the lower colon or rectum. Most people confuse this bleeding with that of hemorrhoids, which delays cancer diagnosis.
However, if you are not experiencing other symptoms of hemorrhoids such as pressure on the anal area, bleeding can be due to colon cancer and needs immediate medical evaluation.
6) Change in Bowel Habits
The polyps are small, abnormal growth of cells formed in the lining of the colon, known as colon mucosa. When colon cancer is staged according to TNM classification, polyps are classified as “stage 0″ or ‘pre-cancerous” stage that have the ability to grow faster and turn into tumor cells over time.
When polyps turn into cancer, they usually start putting pressure on surrounding tissues, affecting bowel habits and triggering certain symptoms. Any change in the stool consistency or frequency coupled with other symptoms discussed above can be indicative of colorectal cancer. The change in bowel habits can be either constipation or diarrhea.
● Constipation
Chronic constipation for more than 2 weeks can be a sign of cancer in the colon, especially if it is not relieved by taking laxatives or other constipation-soothing drugs. According to a 2011 study published in the Asian Pacific Journal of Cancer Prevention, there is a strong link between colon cancer and constipation. It has also demonstrated that chronic constipation is a major risk factor for developing colon cancer. Another study on colorectal cancer research also supported the hypothesis that polyps and tumor growth can obstruct the colon and make it very difficult to eliminate waste products, leading to constipation.
Immediately consult your doctor if you are experiencing altered bowel movements for more than a week or two. It can be an early symptom of colon cancer, and prompt diagnosis can increase the chance of recovery.
● Diarrhea
Like constipation, lingering diarrhea can also be an early sign of colon cancer. When tumor cells grow in size, they start putting pressure on surrounding areas and stimulate the nerve signals. The brain decodes these signals as if your body needs to cleanse itself of excess metabolic waste products. This results in a constant leaking of water and other food contents in the form of soft stools or diarrhea. Some people with colon cancer may also experience frequent abdominal pain, gas, nausea, and vomiting.
When diarrhea lasts for more than a week or so, it can lead to dehydration. This, in turn, can cause depletion of energy sources and stimulate the weight loss process, thereby worsening the symptoms of colon cancer.
7) Gas and Bloating
Gas and bloating are the sister symptoms that often accompany other gut symptoms like diarrhea, constipation and abdominal pain. The majority of people experience these symptoms occasionally. However, if they become chronic and associated with other symptoms mentioned here, it may indicate a tumor growing in the colon.
A growing tumor tends to block the lumen of the colon. Depending on the stage (severity) of the disease, this blockage may prevent passing gas, and may lead to progressive bloating.
8) Bowel Obstruction
Obstruction of the bowel can be due to large-sized polyps or a grown-up tumor. Both tend to stop digestive waste from passing through the bowel and leads to various symptoms such as;
- Constant inflammation of the tummy
- Intermittent and severe abdominal pain – The pain is more intense over the location of the obstruction and always provoked by eating
- Unintentional weight loss – due to poor processing of food, water, and nutrients. If you have already lost some pounds, a bowel obstruction can stimulate the process.
- Vomiting – The blockage and regurgitation of food particles lead to occasional vomiting.
Obstruction of the bowel is a medical emergency, that if not treated promptly, can cause necrosis (death of tissues due to stoppage of blood supply). If you are already diagnosed with colon cancer and experience sudden and sharp pain in the abdomen along with other symptoms of bowel obstruction, you should consult your health care provider quickly to evaluate and treat the underlying cause.
9) Anemia
Anemia is a symptom as well as complication of many types of cancers, including colon cancer. It refers to low hemoglobin or a low number of red blood cells that results in reduced oxygen supply to the organs. The most obvious symptom of anemia includes paleness of the skin and eyes, shortness of breath, dizziness, a fast or irregular heartbeat, and cold hands and feet. It can also contribute to the development of chronic fatigue and weakness.
Iron deficiency anemia usually develops in right-sided colon cancer. This happens when there is continuous bleeding secondary to the damage to the blood supply. Reduced capacity of red blood cells to carry and deliver oxygen and the collection and excretion of metabolic waste products also affect healthy cells.
A recent study published in the British Journal of Cancer shows that there is a strong connection between cancers (colon cancer among them) and anemia. The same study also confirms iron deficiency as a predictor of colon cancer, especially that affecting the right side of the colon.
If your skin is turning pale or you often feel fatigue after day-to-day activities like walking or climbing the stairs, consult your physician to get your hemoglobin levels checked.
10) Metastatic Colon Cancer Symptoms
Besides local symptoms discussed above, colon cancer can cause various symptoms due to metastasis (spread) of the tumor to the other organs. Metastatic symptoms usually develop in the advanced stages (stage 4) of the colon cancer and depend on the size of the tumor, the involvement of remote organs and lymph nodes. For instance:
- If the lungs are affected, the typical symptoms will be difficulty breathing, shortness of breath, coughing, fatigue, and chest pain.
- Symptoms may include pain, fractures, and high calcium levels when the tumor has spread to the bones.
- If the lymph nodes of the abdominal organs such as stomach and pancreas are affected, it may cause a swollen belly, bloating, and loss of appetite.
- If the tumor has spread to the liver through lymph nodes, symptoms may include swelling of the hands and feet, nausea, fatigue, jaundice, and increased abdominal girth.
- If the brain is affected, the usual symptoms may include severe headaches, confusion, blurred or double vision, memory loss, seizures, and difficulty speaking.
» Now, let’s discuss the stages of colon cancer.
Colon Cancer Stages
A scale of numbers from 0 to 4 or a letter X is specified for each category. This scale represents the severity of the disease. If the number is small, the disease is less severe. If there is a higher number, the disease is more severe. For example: as T represents the size of the tumor, T1 is considered as the tumor with a smaller size, T2 is greater in size than T1 and T3 is much bigger than both T1 and T2 and so on to T4. Whereas the letter “X” is used when the information about the disease is not determined.
Similarly, N0 indicates no lymph node involvement, N1 means less than 4 lymph nodes are affected and N2 describes the involvement of more than 4 lymph nodes. M0 means no metastasis (the tumor is still localized and has not yet spread to the other organs) while M1 indicates the active metastasis of tumor tissues.
According to the TNM classification, colon cancer is classified into four different stages using some specific numbers and letters that are assigned to each category. These numbers are assigned according to the structure and shape of the colon, the size of the tumor and explain how much the tumor has spread outside of the colon. These stages include;
A) Stage 0 Colon Cancer
This stage is considered a non-cancerous stage that has the tendency to progress to the cancerous changes. Generally, stage zero means polyps or small abnormal growths inside the colon or rectum. These polyps are usually formed in the lining of the colon, a tissue known as mucosa. At an early stage, these abnormal outgrowths are restricted to one place, and no further spread has observed in the surroundings. This is termed as “Carcinoma in situ”. They should be removed immediately when observed. If not treated at an early stage, they may turn into cancer cells.
B) Stage I Colon Cancer
This is the actual stage where the cancer starts developing. In this stage, cancer spreads into the mucosa which is the internal lining of the colon and may also involve submucosa. If not diagnosed and treated at the submucosal level, it has also the tendency to spread to the muscles. This stage is written as T0 or T1, depending on the size of the tumor. As there is no proof of tumor spreading into the lymph nodes and other organs surrounding the infected part, TO or T1 is usually accompanied with N0 and M0.
C) Stage II Colon Cancer
This stage of colon cancer is divided into the following three types:
Stage IIA: Cancer does not affect the organs or lymph nodes in this stage. They involve mucosa and further spread into the serosa, which is the tissue of the intestine made up of serous membrane.
Stage IIB: In this stage, cancer affects all the layers of the colon or rectum (mucosa, submucosa, and serosa). However, lymph nodes or distant organs are not infected yet.
Stage IIC: In this stage, cancer also spreads to involve the nearby lymph nodes, but the distant organs and lymph nodes are still unaffected.
D) Stage III Colon Cancer
Stage III colon cancer involves a compromise of the lymph nodes and can be divided into three categories:
Stage IIIA: This stage of cancer starts becoming severe. Cancer has now spread from mucosa to submucosa. And it is entering into the muscles. Cancer may spread into less than three nearby lymph nodes from where the primary tumor started.
Stage IIIB: Cancer has now gone through the colon’s outermost layer and it starts to affect 4 or more lymph nodes, nearby organs and tissues. Distant organs are still safe from the tumor.
Stage IIIC: The tumor has spread to involve four or more regional lymph nodes. Nearby organs are also affected. This stage is very difficult to treat and require long and thorough treatment. The typical options available to treat this stage of colon cancer are aggressive chemotherapy, radiotherapy and multiple surgical procedures combined.
E) Stage IV Colon Cancer
Stage 4 is the most advanced stage and indicates metastasis of the tumor tissue. In this stage, the tumor tissue spreads to distant organs such as the liver, lungs or even the brain. Stage 4 is also further divided into two classes: Stage IVA and Stage IVB. When cancer affects only one organ, it is known as Stage IVA of colorectal cancer. If more than one organ is involved, it is known as Stage IVB of colon cancer.
Low-grade VS High-grade
Cancer is also classified on the basis of grades. The lower grade represents a less severe cancer, while a higher grade represents more advanced levels.
The cancer cells get rankings when they are observed under a microscope. The microscopic features of the tumor cells elaborate the differentiation of the cancer cell. If the tumor looks less differentiated, a lower grade is given. The higher grades are given to the cells which are highly differentiated from the parent tissue and looks more abnormal. The higher the differentiation between cells, the higher will be their grade and malignancy.
Conclusion
There are numerous causes of colon cancer. It includes smoking, drinking alcohol in excess, diabetes, obesity, aging, hereditary, and less active lifestyle etc. Usually, colon cancer is diagnosed in people at the age of 50. But those with a family history of colorectal cancer can develop this disease at an early stage. There are a number of screening tests to detect colon cancer at initial stages. If diagnosed earlier and prompt treatment is given during the stage 1 or stage 2, the chances of full recovery are brighter. However, if the disease progressed to more advanced stages, it is very difficult to control the rapid spread of cancer.