The large intestine in humans is divided into the colon, rectum, and anus. The colon is the largest part of the large intestine. Various types of cells are present in the colon. Mutations in one or more cell types may result in uncontrolled growth and division. This condition involving uncontrolled growth and division of colon cells leading to tumor formation is known as colon cancer or colon carcinoma.
Although colon carcinoma may develop in people of any age, it most often occurs in the elderly. The initial stage of colon cancer is the formation of polyps. Although not all polyps turn into cancer, the presence of polyps significantly increases the risk of colon cancer. Men are at a higher risk of developing this condition than women.
Colon carcinoma is slowly becoming one of the most prevalent cancers in India. The survival rates for this disease are relatively lower in India as compared to developed countries, and probable reasons for this include delayed diagnosis and limited access to better quality healthcare.
Also, another important aspect is that colon cancer incidence in India is likely under-reported due to underdiagnosis and limited access to healthcare in rural areas.
Based on the type of cell that it arises from, colon cancer is classified into various types. Different types of colon cancer include:
Several glandular cells are present in the colon and produce mucus. The mucus is important for lubrication and protection of the internal wall of the colon. The cancer of these gland cells in the colon is known as colon adenocarcinoma. It is the most common type of colon carcinoma.
Squamous cell carcinoma arises from squamous cells, and it is exceptionally uncommon, as compared to other types of colon cancer.
Carcinoid tumors are types of neuroendocrine tumors that are slow-growing. Carcinoid tumors usually do not cause any symptoms and are diagnosed incidentally. Due to their slow growth rate, they have very little potential to metastasize. In many cases, there will be more than one carcinoid tumor.
Colon lymphoma, or colonic lymphoma, is one of the relatively rare types of colon cancer, and it arises from the lymphatic system in the colon. Non-Hodgkin lymphoma is a more common form of colonic lymphoma.
These rare lesions in the colon occur due to the formation of abnormal cells in the tissues of the colon. The risk of gastrointestinal stromal tumors is increased by certain genetic factors. The symptoms of gastrointestinal stromal tumors include vomiting and blood in the stool. GISTs often begin as benign tumors and later become cancerous.
Leiomyosarcoma of the colon is an extremely invasive and rare tumor. The tumor develops in the muscularis propria, which is the smooth muscle layer of the gastrointestinal tract.
Melanomas of the colon are exceptionally rare. Melanoma is a type of skin cancer that can rarely metastasize into the colon. In exceedingly rare cases, melanoma-causing cancer cells (cancerous melanocytes) develop in the colon, and such cases are termed primary colonic melanoma.
Following are the colon cancer stages:
This stage is known as cancer in situ. The cancerous cells are present only in the inner lining of the colon, or mucosa.
Cancer develops in the mucosa and muscular layers of the colon. No cancer growth occurs in the nearby lymph nodes or tissues.
The cancer invades the wall of the colon, the muscle of the abdominal lining (visceral peritoneum), or the wall of the colon and nearby structures but does not spread to nearby lymph nodes.
The cancer has grown to the inner muscular lining with 1 to 3 lymph nodes, or the bowel wall or surrounding organs with 1 to 3 lymph nodes, or ≥ 4 lymph nodes, irrespective of the depth of cancer growth.
Cancer has spread to only one distant site, such as the lungs or liver, or to more than one distant site, or to the peritoneum, with or without invading distant organs.
Learning about the different signs and symptoms of colon cancer and understanding the possible causes associated with it is important as these help patients receive an accurate diagnosis and appropriate treatment. Some colon cancer patients may not show any symptoms initially; however, as the disease progresses, they start exhibiting symptoms. Therefore, along with keeping an eye on the symptoms, it is also necessary to opt for regular health checkups to catch colon cancer in its early stages.
Colon cancer is found to be more common in individuals who have the following risk factors:
1. Above 50 years of age
2. Family history of colon cancer
3. Medical history of polyps
4. Underlying conditions, such as diabetes, IBD, and obesity
5. Radiation exposure for other abdominal cancer treatment
6. Excessive tobacco and alcohol consumption
Colon cancer symptoms do not present early in most patients. Once the disease starts progressing, the patients start experiencing symptoms. Symptoms of colon cancer in women are similar to signs of colon cancer in men. Early colon cancer symptoms, if present, include:
Any change in the bowel habits, such as frequent constipation or diarrhea, maybe a sign of colon cancer. Patients should also consult a doctor if they have narrowed stools.
Blood in the stool is one of the most common colon cancer symptoms. However, bloody stool may also be due to hemorrhoids or anal tears. Patients should consult the doctor if they have dark black or brown stools as this helps them with a definitive diagnosis.
Patients with colon cancer may experience rectal bleeding. That said, other conditions like anal fissures, hemorrhoids, IBS, etc., can also cause rectal bleeding. For a conclusive diagnosis, one must see a doctor.
Bleeding due to colon cancer may result in anemia. Anemia causes weakness and fatigue, which may also be the early symptoms of colon cancer.
Unintended weight loss is sometimes one of the early signs and symptoms of colon cancer. Cancer results in weight loss due to various mechanisms. These include difficulty eating due to nausea and lack of appetite. Further, cancer causes inflammation in the body. The inflammatory mediators also alter the metabolism and lead to weight loss.
Patients with colon cancer also experience vague abdominal cramps or pain. It may be due to the invasion of cancer into the walls of the colon or the spread of the tumor to nearby structures. It is one of the early symptoms of colon cancer. It could also be one of the signs of advanced-stage colon cancer.
Gas, bloating with a feeling of dullness, and abdominal pain are common signs of colon cancer. Bloating occurs due to the inability to pass gas because of obstruction by the tumor.
Nausea and vomiting may also be experienced by patients with colon cancer due to obstruction by the tumor in passing gas or solid or liquid waste.
Patients with advanced-stage colon adenocarcinoma experience various symptoms, such as unexplained weight loss, rectal bleeding, bloody stool, and pain in the stomach.
Patients with squamous cell carcinoma experience unintended weight loss, altered bowel habits, abdominal pain, and rectal bleeding.
The majority of patients with carcinoid tumors do not experience any symptoms. Symptoms, if present, include bleeding, weight loss, colon obstruction, constipation, and abdominal pain.
Patients with colon lymphoma have weakness, diarrhea, night sweats, gastrointestinal bleeding, bowel obstruction, fever, unintended weight loss, and abdominal pain.
Symptoms of gastrointestinal stromal tumors include tiredness, blood in the stools, and abdominal pain.
Patients with leiomyosarcoma experience several non-specific symptoms, including obscure or fresh rectal bleeding, abdominal pain, intra-abdominal hemorrhage, bowel obstruction, altered bowel habits, weight loss, and a frequent urge to use the restroom.
Patients with colon melanoma experience nausea and vomiting, irregular and difficult defecation, and abdominal pain.
Patients usually ask about what causes colon cancer. Some of the common colon cancer causes include:
Colon cancer mostly occurs in people over the age of 50. However, there is an increasing trend of colon cancer occurrence in people under 50.
People with a family history of colon cancer have a higher risk of developing it. Certain inherited conditions, such as Lynch syndrome, are also reasons for colon cancer.
Those with colorectal polyps also have an increased risk of developing colon cancer.
IBD, such as ulcerative colitis and Crohn's disease, may also cause colon cancer because of persistent inflammation in the colon.
Obesity increases the likelihood of developing colon cancer. It also increases the risk of death due to colon cancer. Excess weight causes an imbalance in hormone levels and other substances that regulate the division of cells.
Physically inactive people may have colon cancer. It may be due to increased body weight and obesity.
Tobacco consumption and excessive intake of alcohol may also be possible causes of colon cancer.
Diabetes causes colon cancer through various mechanisms. High levels of sugar and insulin create a favorable environment for tumor formation in the colon.
Reports suggest that a low dose of aspirin may have a protective effect against colon cancer.
Radiation exposure, as a part of radiation therapy for treating other abdominal cancers, may also serve as one of the possible colon cancer causes.
One must see a gastroenterologist if they are experiencing persistent GI issues and other symptoms of colon cancer. This is important for timely detection and treatment of colon cancer.
When a patient starts experiencing colon cancer symptoms, they must immediately see a doctor for a proper evaluation. The doctor may begin with a physical examination and medical history assessment before any test in order to understand the causes of the symptoms.
If the colon cancer diagnosis is confirmed, the doctor may further proceed with staging. Upon obtaining crucial information like the type of colon cancer, its stage, its grade, its exact location, and the patient’s overall health status, the doctor, along with their team, will devise a personalized colon cancer treatment plan.
Oncologists are often asked about how to detect colon cancer at home or through self-tests. It is not possible to detect colon cancer at home, as it requires a battery of specialized tests to be diagnosed accurately. The following are the most recommended tests for colon cancer diagnosis:
The doctor may advise the patients to undergo fecal occult blood tests to determine the presence of blood in the stool. This is because the blood vessels in the cancerous tumor are generally fragile and easily damaged during stool passage.
The test is also called a multi-targeted stool DNA test. It allows the doctors to determine the abnormalities in the DNA of the cancerous cells. The test also identifies the hidden blood in the stools.
This test is performed with the assistance of a colonoscope. The colonoscope comprises a thin, long tube for easy insertion into the anus, with a camera and light source to view the internal tissues of the colon.
Colonoscopy is a method to visualize the internal tissues of the colon with a colonoscope to detect the presence of abnormal cells or polyps. However, in some cases, the doctors may need to collect the samples after visualizing the abnormal tissues or polyps for further examination (biopsy). In such cases, specialized instruments are inserted through the colonoscope to obtain the samples.
Sigmoidoscopy is a colon cancer test performed with the help of a sigmoidoscope. It is similar to a colonoscope (a thin tube with a camera at the tip). Unlike colonoscopy, which involves the examination of the entire colon, sigmoidoscopy examines only the lower colon.
This test is useful for patients who do not wish to undergo more uncomfortable procedures for colon examination, such as colonoscopy. Virtual colonoscopy involves using computed tomography to detect polyps or abnormal areas of the colon. Further, a colonoscopy is required after a virtual colonoscopy to obtain the tissue samples.
A CT scan is an imaging technique employed to develop high-quality images of the colon with the help of X-rays. Apart from detecting abnormal cells in the colon, the test also determines the spread of cancer to nearby lymph nodes or distant organs, such as the lungs or liver.
Magnetic resonance imaging gives clear images of the colon using strong magnets and radio waves. The doctor may inject a contrast agent, such as gadolinium, to get clearer images before the MRI. MRI may also detect the spread of colon cancer to distant organs, e.g., the liver, brain, or spinal cord.
Unlike other imaging techniques, such as CT and MRI, that provide morphological and anatomical structures of the target site, a PET scan gives detailed information about the metabolism of the tumor. It assists oncologists in differentiating between malignant and benign tumors. The PET scan also helps in staging colon cancer by determining the spread of the tumor to nearby and distant areas.
Once the diagnosis is confirmed, the disease has to be staged to understand the extent of its spread. Based on the information obtained through staging, the doctors devise a customized treatment plan for each case. While staging, various factors, such as tumor size, depth of invasion into the colon wall, lymph node involvement, and the presence of distant metastases, are taken into consideration. Stage 0, stage 1, stage 2, stage 3, and stage 4 are the different stages of colon cancer.
Samples obtained through colonoscopy are sent for a comprehensive laboratory examination. The tissue samples are analyzed under the microscope to determine the presence of cancerous cells.
Genetic testing is also performed on the samples obtained during the biopsy. Genetic testing helps determine the type of gene mutation that has led to the formation of cancer. It is often recommended for patients with advanced colon cancer to identify specific gene mutations to determine their eligibility for targeted therapy.
Once the screening or diagnostic testing is complete, the doctor consults with the patient and provides an appropriate treatment plan. If the patient is diagnosed with polyps, usually no medication is prescribed.
However, the patient may be advised to undergo scheduled monitoring to constantly check if the polyps have developed into colon cancer.
The colon cancer treatment plan is created after considering a myriad of factors, starting from the type of cancer, its stage, and grade to the overall health of the patient. Some of the colon cancer treatment options include:
Surgery is the preferred treatment for early-stage colon cancer. The primary goal of surgery is to remove the tumor. Colon cancer surgery may or may not be followed by other treatments like chemotherapy and radiation therapy.
Polypectomy is a type of colon cancer surgery to remove early-stage colon cancer (stage 1 colon cancer treatment) and polyps. Polypectomy involves the removal of the polyps from the base of the polyps by inserting a wire loop into the colonoscope and passing an electric current through the wire.
Laparoscopic surgery for colon cancer is a minimally invasive procedure for removing the cancerous tissues from the colon. Unlike conventional open colon cancer surgery, laparoscopic surgery involves making small incisions in the abdomen to remove the cancerous tissues. During laparoscopic surgery, the surgeon may also obtain samples of nearby lymph nodes to detect the spread of cancer outside the colon.
Colectomy involves the removal of the colon, partially or completely. If the colon is removed partially, the procedure is known as a partial colectomy, hemicolectomy, or segmental resection. If the colon is completely removed, the procedure is known as a total colectomy. Colectomy is considered an effective cure for colon cancer if the disease is limited to the colon.
Sometimes, the surgeon may remove the nearby lymph nodes to check for cancer. It will help in staging the disease and narrowing the optimal treatment options.
A colostomy is a procedure to form an opening of the colon onto the abdomen to pass stool. It is done when there is a need for intestinal removal, such as in colon, rectal, or anal cancer. An ileostomy is a procedure that involves opening the ileum into the abdomen.
Chemotherapy for colon cancer involves using medications that kill rapidly dividing cells, including colon cancer cells. Chemotherapy is usually prescribed as a combination of various drugs. The delivery of drugs is through the oral or injectable route. Chemotherapy may be administered before the surgery (neoadjuvant chemotherapy) or after the surgery (adjuvant chemotherapy).
Targeted therapy is one of the newer colon cancer treatments. Certain cellular components and pathways are specific to cancer cells, and they are vital for the growth, division, and spread of cancer. Targeted therapy targets those specific molecules and cellular pathways and interferes with the growth, cell division, and proliferation of cancerous cells.
Immunotherapy delivers the drugs that stimulate the immune system to damage the cancerous cells. Drugs delivered under immunotherapy interfere with the processes through which the cancer cells hide from the immune system, thus making them more vulnerable to being attacked by the immune cells.
In radiation therapy for colon cancer, specialists guide high-energy radiation toward the tumor, damaging the cancerous cells. Radiation therapy is usually used in combination with chemotherapy or surgery.
Adjuvant therapy for colon cancer may also be prescribed. As an adjuvant therapy, chemotherapy destroys residual cancer cells after surgery. Another adjuvant therapy for colon cancer is embolization or ablation of the cancer.
Palliative care is recommended for patients with advanced-stage colon cancer. Palliative care aims to manage cancer symptoms and improve the patient's quality of life.
Patients who do not show a desirable response to the standard colon cancer treatments may register themselves in clinical trials where they can access new drugs and treatments whose efficacy is yet to be understood.
Patients must know that the clinical trial team prioritizes patient safety and that they are closely monitored throughout the study.
Lastly, clinical trials are not suitable for all patients. The eligibility criteria may vary depending on the objective of the trial and other parameters. Those patients who are interested in enrolling in clinical trials should have a detailed discussion with their expert team.
HCG is one of the leading comprehensive cancer treatment hospitals in India, with all the facilities available for effectively diagnosing and treating colon cancer. The center is equipped with advanced diagnostic facilities that assist oncologists with accurate colon cancer diagnoses. As one of the best colon cancer treatment hospitals in India, HCG houses advanced treatment facilities to administer modern treatments like immunotherapy, targeted therapy, and minimally invasive surgeries as a part of colon cancer treatment.
Through years of study, we have learned that certain factors can increase the risk of colon cancer. Having these risk factors does not guarantee a colon cancer diagnosis; however, having these risk factors means one has a higher risk of developing colon cancer. Such individuals should pay extra attention to their health, follow appropriate preventive measures, and opt for regular screening to put themselves a step ahead of colon cancer.
Some risk factors for colon cancer are controllable or lifestyle-related, while others are non-controllable or non-lifestyle-related. Lifestyle-related risk factors can be modified, while non-lifestyle-related factors cannot. The most common colon cancer risk factors include:
The colon cancer risk increases with age. Colon cancer is usually found in people over the age of 50. However, in recent times, there has been an increasing trend in the development of colon cancer in people under 50 years of age.
A sedentary lifestyle, involving a poor diet, limited physical activity, and excessive tobacco and alcohol consumption, increases the risk of colon cancer.
People with immediate relatives who have been diagnosed with colon cancer are at an increased risk of developing it. The risk of colon cancer increases with the number of family members diagnosed with the disease. Further, patients with a personal history of colon cancer also have an increased recurrence risk.
Patients with inflammatory bowel disease have persistent pain and inflammation in the bowel. The conditions include Crohn’s disease and ulcerative colitis. Having these conditions is one of the colon cancer risk factors.
DNA alterations that increase the risk of colon cancer are sometimes inherited. The common genetic conditions that increase the risk of colon cancer include Lynch syndrome, Peutz-Jeghers syndrome, and familial adenomatous polyposis.
Individuals on a typical Western diet have an increased risk of developing colon cancer. The Western diet is high in calories and fat and low in fiber. Individuals who regularly consume processed meat, red meat, highly processed carbohydrates, sugary foods, etc., are at a higher risk of colon cancer.
People with obesity are at a higher risk of developing colon cancer and succumbing to it. This is because fat accumulation leads to hormonal imbalance and inflammation, which can trigger tumor formation.
Those who lead a sedentary life also have an increased colon cancer risk. Lack of physical activity increases fat accumulation and obesity, leading to an increased likelihood of colon cancer.
Smokers have a higher risk of developing more numerous and larger colon polyps. It has been found that the risk of colon cancer occurrence is higher in individuals who smoke than in those with a family history of colon cancer.
People who consume moderate to heavy alcohol have a 1.2–1.5 times increased risk for colon cancer compared to people who do not consume alcohol.
Type 2 diabetes increases the risk of colon cancer due to hyperinsulinemia, gastrointestinal motility disorders, and adipose tissue dysfunction.
Those who have received radiation treatment in the past, especially to treat cancer in the abdominal region, are at a higher risk of developing colon cancer.
Environmental factors, such as exposure to harmful toxins, occupational exposure, food intake, and colon cancer awareness, affect the overall risk of colon cancer.
“How to avoid colon cancer?” or “How to prevent colon cancer?” is one question that oncologists around the world are asked every day.
The answer to this question is that there is no known way to prevent colon cancer. However, it is possible to reduce the risk of colon cancer with certain measures. The following measures are found to improve the chances of colon cancer prevention:
Regular screening is one of the most effective measures that can improve the chances of colon cancer prevention. Colon cancer often starts as polyps, and it takes 10 to 15 years for these polyps to become cancerous. Regular screening is especially recommended for high-risk individuals. For more information on the screening tests available for colon cancer and their frequency, one must talk to a specialist.
Incorporating fresh fruits and vegetables into the daily diet reduces the risk of colon cancer. A fiber-rich diet, antioxidants, and whole grains help in the possible prevention of colon cancer.
People who are obese should opt for healthy weight management by limiting calorie intake, consuming a balanced diet, and exercising regularly. People with healthy weight should maintain weight to reduce the risk of colon cancer.
Limiting alcohol consumption can aid in the potential prevention of colon cancer.
Quitting smoking reduces the risk of colon cancer significantly. Numerous studies have reported that non-smokers are at a lower risk of colon cancer than former and current smokers.
Studies suggest a link between adequate water consumption and reduced risk of colon cancer. The mechanism involves early evacuation of the potential carcinogens from the intestine with adequate water intake.
Physical activity helps maintain a healthy weight, lowering the risk of colon cancer.
Several conditions enhance the likelihood of colon cancer. These include obesity, type 2 diabetes, and inflammatory bowel disease. Efficient management of these conditions helps individuals lower their risk of colon cancer.
Minimal or no exposure to environmental pollutants, such as water pollution, air pollution, chemicals in food and soil, and pesticides, reduces the colon cancer risk.
Colon carcinoma may develop in any person. However, some individuals are at increased risk of developing colon cancer. These include individuals with polyps, inflammatory bowel disease, radiation exposure, and inherited medical conditions such as Peutz-Jeghers syndrome, Lynch syndrome, and familial adenomatous polyposis.
Colon carcinoma occurs in the colon and is one of the most common cancers globally. There are various types of colon cancer. The most common are squamous cell carcinoma, lymphoma, adenocarcinoma, and carcinoid tumors.
Colon carcinoma is categorized into various stages depending on the extent of the disease’s spread. Early-stage cancers have a better prognosis than those in advanced stages.
