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OLON  ANCER

  
   

 

Definition:

‘Colon cancer’ refers to a malignant growth in the colon or rectum – Colorectal Cancer.

Colon cancer is the third most common cancer worldwide with a growing tendency.  Men are more often afflicted than women.  The most frequent type of colon cancer is the adenocarcinoma (95% of all colon cancers), a cancer derived from the mucous producing cells and glands in the epithelium of the large intestine.  Other rare types of colon cancer are the squamous cell carcinoma, lymphoma, and others.

Risk factors

The exact cause for the development of colon cancer is not known; however, there are a number of known risk factors, such as:

  • Age – colon cancer usually develops after the age of 50.
  • Diet – colon cancer seems to appear more often in people who eat an unbalanced diet, especially a diet that is rich in fats and calories, and low in fiber.  Alcohol, especially beer, red meat and smoking are all associated with an increased risk of developing colorectal cancer.
  • Polyps – so-called adenomatous polyps, are mushroom shaped growths of the mucosa (the epithelium that lines the inside of the large intestine) of the colon and/or rectum, which occur relatively frequently, especially after the age of 50.  While most of these polyps are benign tumorous growths, some of them harbor the possibility of developing into malignant cancerous growths. 
  • Familial adenomatous polyposis – FAP, is considered a hereditary colon cancer syndrome that carries an almost 100% chance of developing colorectal cancer by the age of 40.
  • Predisposition factors – there is a known familial tendency towards the development of colon cancer, thus, if one family member has been inflicted with colon cancer, there is an increased chance for another family member along the genetic line (children, grandchildren) to develop colorectal cancer at some point in his/her life time.  Also, if a patient has already experienced another type of cancer, such as cancer of the ovary, uterus (womb) or breast, the risk of also developing colon cancer is considerably increased.
  • Chronic infections – such as ulcerative colitis (chronic inflammation of the colonic mucosa with the development of colonic ulcers) and long standing Crohn’s disease affecting the colon can carry an increased risk of exacerbating into colon of cancer. 
  • Virus causing colon cancer – there is an increased chance of developing cancer of the colon, caused by certain subtypes of the Human Papillomavirus, HPV – a virus that is sexually transmitted and considered to be part of the sexually transmitted diseases.

 

Symptoms:

Frequent, albeit non-specific symptoms include changes in bowel habits, in regard to quantity as well as quality of the stool.  Unexplained changes between diarrhea and constipation, which are not based on dietary changes, and the feeling of not having emptied the colon completely, should be reviewed and examined by a medical professional. 

The presences of blood in the stool – a very dark to black colored stool – definitely requires medical attention.  While this sign is not diagnostic of colon cancer, it points to an actively bleeding incidence somewhere along the length of the colon, which needs to be diagnosed (identified) and treated accordingly.  The blood can be caused by an ulcerous lesion such as ulcerative colitis, which is a seriously debilitating disease, and can also exacerbate into colonic cancer.  Bleeding can also derive from surface mucosal injuries of various, often larger size polyps, which can demonstrate a precancerous growth pattern with an increased chance of developing into full blown cancer at some point in time.

Also, the feeling of general malaise, unexplained feeling of fullness, excessive gas production or abdominal cramps, as well as unintended weight loss, continuous tiredness and repeated vomiting are all signs that could be associated with colon cancer.

While all of the above listed symptoms are rather non-specific, and could also be caused by an intestinal infection, they should be worked up by the family practitioner or another physician, who will be able to correctly identify the symptoms, make an accurate diagnosis, and start an appropriate treatment, or conduct further investigations.


 
Diagnosis:

The physician will start with taking a detailed personal and family medical history, followed by a thorough physical examination.

Many tumors can be diagnosed by a rectal exam.  Upon suspicion, further tests will be arranged and performed by specialists; these tests include a barium enema, which is a special kind of x-ray procedure that can detect the presence of polyps.

A colonoscopy, in which a flexible tube will be inserted rectally, allows for a visual inspection of the entire colon, as well as for the possibility to take small tissue samples (biopsy) from suspicious areas of the colonic mucosa or colonic polyps.  These biopsy specimens will then be examined by a pathologist who will render a diagnosis as to the quality (benign or malignant) of the cells (histology).

In addition, a computer tomography – a CT-scan – can provide insight to the presence of possible metastases (malignant satellite tumor growths) in other (non-colonic) organs, such as the liver or lungs, among others.

A diagnosis based on the cancer’s histology will categorize the cancer into either adenocarcinoma (95% of all colon cancers), or other types of cancer, such as squamous cell carcinoma, lymphoma, or even rarer types of cancer. 

Following the proper diagnosis, ‘cancer staging’ will estimate the extent of cancer penetration, evaluating local cancer growth beyond the colon itself, and the degree of lymph node involvement, as well as determine the presence of distant metastases.  The first staging system for colon cancer, which is still being used, is the so-called Dukes classification, comprised of four stages:

  • Stage A - Tumor is confined to the intestinal wall;
  • Stage B - Tumor is invading and penetrating through the intestinal wall into adjacent tissue;
  • Stage C - Regional lymph node(s) are involved with tumor;
  • Stage D - Distant metastases in other organs or tissues.

The most common, currently used staging system is the so-called TNM system, detailing the size of the tumor (T), the extent of lymph node involvement (N), and the presence of distant metastases (M):

  • T – the extent of tumor invasion of the intestinal wall:
    • T0 – no evidence of tumor;
    • TIS – cancer in situ (tumor present, but no mucosa invasion);
    • T1 – invasion through the submucosa into the basement membrane;
    • T2 – invasion into the proper muscle of the bowel wall;
    • T3 – invasion through the outer lining of the intestinal wall (the subserosa);
    • T4 – invasion of surrounding structures (e.g. bladder), or tumor cells present on the free external surface of the bowel;
  • N – the extent of lymph node involvement:
    • N0 – no lymph nodes involved;
    • N1 – one to three lymph nodes involved;
    • N2 – four or more lymph nodes involved;
  • M – the extent of distant metastases:
    • M0 – no metastasis;
    • M1 – metastasis present.  

 
Treatment:

The therapy depends on the extent of the tumor – its grade (histological type of cells) and especially, its stage (size, and presence and extent of metastases).

Benign polyps, as well as so-called precancerous polyps can often be removed surgically and do not require additional treatment; however, the patient needs to be followed and re-examined regularly to identify possible new growth as soon as possible.

Larger tumors and malignant cancer growth may require extensive surgery, such as partial or total removal of the colon, followed by a temporary or permanent artificial anus (colostomy).

Local radiation with high energy x-rays may be necessary to the area of the tumor, and/or a systemic chemotherapy with drugs that are transported by the blood stream throughout the body, in order to kill satellite cancer cells (metastases) may also be required.  Chemotherapy is often used prior to surgery, in order to shrink the tumor, or to slow tumor growth, and is the preferred course of treatment for older patients who may represent a higher risk for surgery.

A so-called biological treatment can follow the operation, but never replace the medical therapy.  The biological treatment is aimed at strengthening the body’s immune system, allowing it to better fight the cancer cells.  This kind of therapy can, and often is also used in combination with chemotherapy and radiation therapy.

Course and prognosis of colorectal cancer depends largely on the type and growth pattern of the cancer.  In addition, one’s own WILL to fight the cancer can have an important influence on the body’s ability to battle the disease.

Side effects of the chemotherapy, such as hair loss, changes in blood profile, nausea, tiredness and more, can be various in extent, depending on the personal profile of the patient, and most of these side effects return to normal after the chemotherapy cycles have been completed.

Follow-up visits to your physician, and specific tests and examinations are extremely important in colon cancer.  Regular controls such as simple blood tests, stool tests or other screening examinations can discover new growths early, and therefore allow restarting an appropriate treatment at the earliest possible point in time.


Prevention:

Cancer screening is a simple and effective way of identifying a cancer in the early stages of development, and is an absolutely necessary way of preventing the recurrence of a previously diagnosed and treated colon cancer.

Since colon cancer often develops from benign polyps, the early detection of those polyps and their subsequent surgical removal are of tremendous importance.  Especially after the age of 50, or earlier if there is a potential familial predisposition, regular controls should be performed, which may include one or more of the following screening tests:

  • Fecal occult blood test – this test detects minimal amounts of blood in the stool, pointing to a possible source of bleeding in the colon.  This test should be performed every one to two years in people over 50, or even more often in patients with a high risk profile (see above);
  • Barium enema – especially in high risk patients, this examination should be performed regularly, in order to identify polyps and tumors in their early developmental phase; 
  • Colonoscopy or sigmoidoscopy – is an examination of the entire colon or the distal (end) segment of the colon, respectively, in which a flexible tube with an optic eye is inserted, which also allows to take a tissue biopsy from suspicious areas.  These examinations should be performed upon suspicion or in high risk patients.

Overall, a balanced diet with less fat containing foods and more fiber seems to have a positive impact, and to lower the risk of developing colon cancer over one’s life time.  It is assumed that the slow passage of fatty foods and deeply fried (red and white) meats, can release mucosa damaging heterocyclic amines which harbor carcinogenic (cancer promoting) substances.  Therefore, cutting down on these kinds of foods while concomitantly adding supplemental fiber to the daily diet, which is thought to ‘dilute’ the damaging substances, as well as to fasten the passage of the food products through the colon (and thus limiting the exposure of the damaging substances to the colonic mucosa), is believed to provide some protective effects.

A series of tests have also shown that vitamins, especially vitamin E and D, as well as multivitamins, supplemented with folic acid, harbor certain protective effects.
 
In 2006, a first type of vaccine was developed, which is, however, still in the early stages of development and may take several more years until its efficiency and safety have been tested in clinical trials, prior to its availability to the market.

     

                                                                               

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