What are the other Names for this Condition? (Also known as/Synonyms)

• Bowel Cancer
• Colon and Rectum Cancer
• Colorectal Cancer (CRC)

What is Colon Cancer? (Definition/Background Information)

• Colon Cancer is a malignant tumor of the colon and rectum that is observed in adult males and females worldwide. Since Rectal Cancer shares many similar features with Colon Cancer, they are normally grouped together and also known as Colorectal Cancer (CRC)
• The most common type of Colon Cancer is colorectal adenocarcinoma. Since colorectal adenocarcinomas constitute a vast majority of the cases (over 90% of the cases), the term Colon Cancer generally refers to the adenocarcinoma type
• Other uncommon subtypes of Colon Cancer include lymphomas, gastrointestinal stromal tumors, and sarcomas, among others. There are many variants of colorectal adenocarcinoma too; the following are some of the well-described and well-recognized ones:
  • Mucinous adenocarcinoma
  • Signet ring-cell carcinoma
  • Medullary carcinoma
  • Serrated adenocarcinoma
  • Cribriform comedo-type adenocarcinoma
  • Micropapillary adenocarcinoma
  • Adenosquamous carcinoma
  • Spindle cell carcinoma
  • Undifferentiated carcinoma
• Some of the other less frequently noted Colon Cancer types include:
  • Gastrointestinal carcinoid tumor: It forms in the lining of the gastrointestinal tract
  • Gastrointestinal stromal tumor (GIST): It is a type of tumor that occurs in the gastrointestinal tract
  • Neuroendocrine carcinoma (NEC): It arises from the neuroendocrine cells and are classified as low-grade and high-grade tumors
  • Lymphoma: This is a malignant tumor of the lymphocytes, which are types of blood cells. Some are slow-growing, while other are potentially aggressive. There are different lymphoma subtypes, and it is important to identify these since the treatments can vary from one type to another
  • Sarcoma: It is a malignant tumor that arises from the mesenchymal and stromal cells. In many cases, sarcomas are aggressive requiring multidisciplinary team to manage and treat the malignancy
  • Melanoma: It is a tumor of the melanocytes present in skin; however, rarely they are present in the colon and rectum
• The distribution of Colon Cancer shows a wide variance between the developed and developing geographical regions. The incidence rates are much higher in countries such as USA, Canada, Australia, and certain European nations, compared to Southeast Asian and African countries
• The risk factors, cause, signs and symptoms, complications, and treatment protocols may vary according to the specific Colon Cancer type that is noted in the individual. The prognosis of Colon Cancer depends on the type and stage of cancer observed

According to the World Health Organization (WHO) Classification of Tumors (5th Edition), Tumors of the Colon and Rectum include the following types:

Benign epithelial tumors and precursors:

• Colorectal serrated lesions and polyps
  • Hyperplastic polyp
  • Hyperplastic polyp, microvesicular type
  • Hyperplastic polyp, goblet cell-rich type
  • Sessile serrated lesion
  • Sessile serrated lesion with dysplasia
  • Traditional serrated adenoma
  • Serrated adenoma, unclassified
• Conventional colorectal adenoma
  • Tubular adenoma NOS
  • Tubulovillous adenoma NOS
  • Villous adenoma NOS
  • Low-grade glandular intraepithelial neoplasia
  • High-grade glandular intraepithelial neoplasia
  • Advanced adenoma
• Inflammatory bowel disease-associated dysplasia of the colorectum

Malignant epithelial tumors:

• Colorectal adenocarcinoma
  • Micropapillary adenocarcinoma
  • Medullary adenocarcinoma
  • Mucinous adenocarcinoma
  • Serrated adenocarcinoma
  • Poorly-cohesive adenocarcinoma, including signet-ring cell carcinoma
  • Adenosquamous carcinoma
  • Adenoma-like adenocarcinoma
  • Undifferentiated carcinoma
  • Carcinoma with sarcomatoid components
• Colorectal neuroendocrine neoplasms
  • Neuroendocrine tumor (NET)
  • Neuroendocrine carcinoma (NEC)
  • Mixed neuroendocrine-non-neuroendocrine neoplasm (MiNEN)

Who gets Colon Cancer? (Age and Sex Distribution)

• Colon Cancer is generally seen in middle-aged and older adults
• Both males and females are affected, although a greater number of cases are observed in males
• All races and ethnic groups are at risk for the condition, although:
  • A higher number of cases (per million population) are reported from well-developed regions of the world such as Australia and New Zealand, Japan, USA and Canada, and European countries
  • Parts of Africa, India, Pakistan, and other underdeveloped/developing geographical regions report a much lower incidence
  • The highest risk for Colon Cancer are reported among the Ashkenazi Jews (Jews of Eastern European descent)

What are the Risk Factors for Colon Cancer? (Predisposing Factors)

The predisposing factors for Colon Cancer varies from one cancer subtype to the other. In general, the following factors are known to increase the risk for adenocarcinoma of colon that represent a vast majority of Colon Cancers:

• Advancing age
• Presence of certain genetic disorders such as:
  • Lynch syndrome or hereditary nonpolyposis colorectal cancer (HNPCC)
  • Familial adenomatous polyposis
  • Gardner syndrome
  • Peutz-Jeghers syndrome
  • MUTYH-associated polyposis (MAP)
• Positive family history of Colorectal Cancer or precancerous lesions in the colon or rectum
• Chronic inflammatory bowel disorders such as Crohn’s disease, ulcerative colitis, and schistosomiasis
• Consuming a high calorie diet
• Meat consumption (including animal fat) and leading a sedentary lifestyle
• Presence of premalignant lesions including adenomatous colon polyps and serrated colon polyps
• Alcohol consumption that is moderate to high
• Obesity or being overweight may increase the risk
• Type 2 diabetes
• Radiation therapy to the pelvic region for cancer
• Surgery for bladder cancer treatment
• Smoking tobacco may increase the risk

It is important to note that having a risk factor does not mean that one will get the condition. A risk factor increases one’s chances of getting a condition compared to an individual without the risk factors. Some risk factors are more important than others.

Also, not having a risk factor does not mean that an individual will not get the condition. It is always important to discuss the effect of risk factors with your healthcare provider.

What are the Causes of Colon Cancer? (Etiology)

• Presently, the cause of development of Colon Cancer is generally unknown. The cause may vary from one Colon Cancer subtype to the other
• Research scientists believe that the cause of the condition is mostly due to inherited or acquired genetic mutations, influenced by factors that include food and lifestyle habits such as high-fat, high-calorie diet and sedentary lifestyle

What are the Sign and Symptoms of Colon Cancer?

The signs and symptoms of Colon Cancer varies from one cancer subtype to the other. In general, the signs and symptoms of adenocarcinoma of colon, which represent a vast majority of Colon Cancers, may include:

• Typically, a single mass-like a polyp is noted; ulceration of the tumor is common, especially when it is large
• It can cause narrowing of the colon
• Passing of fresh blood in stool (hematochezia) and anemia is observed, if bleeding from the tumor is observed
• Change in bowel habits; increased episodes of constipation may be noted, due to stool being obstructed by the tumor mass
• Severe constipation can cause enlarged intestine (abdominal distention) and abdominal pain
• Sometimes, perforation of the intestinal walls may occur
• Fever, unintended weight loss, and fatigue/tiredness
• The symptoms may vary based on location of tumor in the colon
• Signs and symptoms of any underlying genetic disorder, if present, may be noted

In some cases, the malignancy may be detected while conducting diagnostic imaging tests for other medical conditions, since no symptoms may be observed.

How is Colon Cancer Diagnosed?

The diagnosis of Colon Cancer can vary from one cancer subtype to the other. In general, the diagnostic tests and exams for adenocarcinoma of colon, which represent a vast majority of Colon Cancers, may include:

• Complete evaluation of family (medical) history, along with a thorough physical examination
• Stool sample analysis
• Screening colonoscopy: Some subtypes of Colon Cancers may be diagnosed during colonoscopies. A colonoscopy is a test that allows the physician to look at the inner lining of the colon and rectum. A typical colonoscopy involves using a thin, flexible tube (called a colonoscope), with an attached video camera, to view the colon and rectum
• Lower gastrointestinal series, which are a combination of analysis methods, combining X-rays and barium to visualize the intestinal region
• Imaging studies, such as MRI scan, transrectal ultrasound scan (TRUS), scintigraphy, and PET scan, may be performed to detect tumor invasion and metastasis
• Tissue biopsy of the tumor:
  • A tissue biopsy of the tumor is performed and sent to a laboratory for a pathological examination. A pathologist examines the biopsy under a microscope. After putting together clinical findings, special studies on tissues (if needed) and with microscope findings, the pathologist arrives at a definitive diagnosis. Examination of the biopsy under a microscope by a pathologist is considered to be gold standard in arriving at a conclusive diagnosis
  • Biopsy specimens are studied initially using Hematoxylin and Eosin staining. The pathologist then decides on additional studies depending on the clinical situation
  • Sometimes, the pathologist may perform special studies, which may include immunohistochemical stains, molecular testing, and very rarely, electron microscopic studies to assist in the diagnosis

Many clinical conditions may have similar signs and symptoms. Your healthcare provider may perform additional tests to rule out other clinical conditions to arrive at a definitive diagnosis.

What are the possible Complications of Colon Cancer?

The complications of Colon Cancer can vary from one cancer subtype to the other. Some potential complications include:

• Emotional and psychological stress due to cancer diagnosis
• Intussusception: When one part of the intestine pushes itself into another part of the intestine, causing obstruction of the bowel necessitating surgical correction
• Tumor infiltration to the pelvic region
• Metastasis to local and regional sites; spread of tumor to the lymph nodes
• Recurrence of the tumor after treatment, especially due to partial surgical removal
• Anastomotic leak; leakage of GI tract contents following surgical procedures, which can result in severe infection and even sepsis
• Side effects from cancer treatment such as chemotherapy and radiation therapy

How is Colon Cancer Treated?

The treatment of Colon Cancer may depend upon a consideration of the following set of factors:

• The histological subtype of Colon Cancer: This is the most significant factor which will help the healthcare provider decide upon the treatment modality to be considered based on the specific Colon Cancer variant diagnosed in the individual
• Stage of the cancer
• Size and location of the tumor
• Severity of the signs and symptoms
• Age of the individual
• Overall health status of the individual
• The treatment preferences of the individual

Following staging of the Colon Cancer subtype, it may be treated in the following manner:

• Surgery may be performed in many of the cases deepening on the evaluation by a healthcare expert
• In case of lymph node metastasis, surgery may be followed by chemotherapy and/or radiation therapy (adjuvant therapy)
• In case of rectal carcinoma, chemotherapy and/or radiation therapy, to shrink tumor before surgery, may be provided (neoadjuvant therapy)

The treatment measures include the following:

• Surgical removal of the entire tumor may be the preferred method of treatment in some cases of Colon Cancer
• In case of cancer spread to local and distant region, ablation and embolization techniques may be used
  • In ablation, the cancer is destroyed without surgically removing them using high-energy radio waves (called radiofrequency ablation), injecting the tumor with ethanol (called ethanol/alcohol ablation), or by using extremely cold temperatures to freeze them using a probe (called cryotherapy)
  • In embolization, the blood flow to the tumor is minimized or obstructed through techniques termed as arterial embolization, chemoembolization, or radioembolization
• Chemotherapy: This approach uses a combination of drugs to kill the cancerous cells and can be used in patients, for all stages of the tumor
  • There can be severe side effects including fatigue, nausea, hair loss, anemia, high risk of infection, and drug-specific reactions
  • Chemotherapy can be administered as a pill, liquid, shot, or intravenously
• Radiation: Radiation therapy is the use of high-energy radiation waves to kill cancer cells, by destroying their DNA
  • This treatment modality may be used in combination with chemotherapy
  • The radiation may be administered by a machine placed outside the body, or by placing a radioactive material inside the body
  • The side effects of radiation therapy include nausea, vomiting, fatigue, pain, risk of cancer later in life, and risk of heart disease
  • Radiation can damage healthy cells in addition to cancer cells, causing further complications
• Supportive treatment: Steroids, blood transfusions, anti-nausea medications, and antibiotics, may be used as supportive therapy. In combination with other treatment measures, these can help combat the symptoms of immunodeficiency
• Undertaking treatment of underlying inflammatory bowel diseases/genetic disorders, as necessary
• Targeted drug therapy: Specific medications are administered periodically to stop tumor growth, particularly during the advanced stages
• Immunotherapy: A patient’s immune system is activated to combat the cancer in this kind of therapy

Regular observation and periodic checkups to monitor the condition is highly recommended following treatment.

How can Colon Cancer be Prevented?

Presently, there are no specific methods or guidelines to prevent the formation of Colon Cancer/Colorectal Cancer. However, if it is associated with a genetic disorder, the following may be considered:

• Genetic counseling and testing: If there is a family history of the condition, then genetic counseling will help assess risks, before planning for a child
• Regular health check-ups might help those individuals with a history of the condition in the immediate family and help diagnose the tumor early

Factors that can help reduce the risk for cancers of the colon and rectum may include:

• Screening colonoscopy: It is important to undergo routine colonoscopy screenings as one gets older (over the age of 45-50 years), to ensure early detection of colon tumors or cancers
• Consuming a diet that is rich in whole grains, vegetables, and fruits
• Taking foods rich in vitamin D and calcium
• Physical activities and regular exercising
• In women, estrogen replacement treatment
• Long-term use of non-steroidal anti-inflammatory drugs (NSAIDs)
• Taking early and appropriate treatment for inflammatory bowel diseases if any
• In order to avoid a relapse, or be prepared for a recurrence, the entire diagnosis, treatment process, drugs administered, etc. should be well-documented and follow-up measures initiated

Regular medical screening at periodic intervals with blood tests, scans, and physical examinations are mandatory. Often several years of active vigilance are crucial and necessary.

What is the Prognosis of Colon Cancer? (Outcomes/Resolutions)

The prognosis mainly depends on the specific subtype of Colon Cancer noted in the individual.

• With prompt diagnosis and appropriate treatment, the prognosis may be favorable in some cases. In case of colorectal adenocarcinoma, the overall 5-year prognosis during the initial stages is about 90%
• Once the type of Colon Cancer subtype is known, then the stage of the malignancy is the most important prognostic factor. A poor prognosis is dictated by high-grade tumors, advanced stages, and positive surgical margins (indicating that some cancer cells are left behind following surgery)
• In general, the prognosis of Colon Cancer depends upon a set of factors that include: 
  • Histological subtype of the Colon Cancer
  • Stage of tumor: With lower-stage tumors, when the tumor is confined to site of origin, the prognosis is usually excellent with appropriate therapy. In higher-stage tumors, such as tumors with metastasis, the prognosis is poor
  • Overall health of the individual: Individuals with overall excellent health have better prognosis compared with those with poor health
  • Age of the individual: Older individuals generally have poorer prognosis than younger individuals
  • The size of the tumor: Individuals with small-sized tumors fare better than those with large-sized tumors
  • Individuals with bulky disease have a poorer prognosis
  • Involvement of vital organs may complicate the condition
  • The surgical resectability of the tumor (meaning if the tumor can be removed completely) - it is a rare option
  • Whether the tumor is occurring for the first time or is a recurrent tumor. Recurring tumors have worse prognosis compared to tumors that do not recur 
  • Response to treatment: Tumors that respond to treatment have better prognosis compared to tumors that do not respond to treatment
  • Progression of the condition makes the outcome worse
• The combination chemotherapy drugs used, may have some severe side effects (such as cardio-toxicity). These chiefly impacts the elderly adults, or those who are already affected by other medical conditions. Tolerance to the chemotherapy sessions is a positive influencing factor

An early diagnosis and prompt treatment of Colon Cancer generally yields better outcomes than a late diagnosis and delayed treatment.

Additional and Relevant Useful Information for Colon Cancer:

The following article link will help you understand other cancers and benign tumors:

http://www.dovemed.com/diseases-conditions/cancer/