Colon Cancer

COLON CANCER

5 Sections of large intestine : Right colon Transverse colon Descending colon Sigmoid colon Rectum

Difference between Colon and Rectum Tube - shaped organ inside abdomen stretch from right side of abdomen over to the left like an upside down ”U”

Muscular bands of the colon splay out and create a pouch (last 15 cm of large intestine)

4 layers of colon : Mucosa

-Innermost layer of colon Submucosa -Lies below mucosa -Contain microscopic blood vessels & lymph channels that supply the colon Muscularis -Push the contents of colon toward rectum Serosa -Outermosts layer of tissue

Colon cancer üCaused by polyps (abnormal mucosal growth) üSurgery required for its removal differs depending on the segment of colon involved

Polyps

Definition 



of polyp:

- any growth arise from the intestine and protruding into the lumen



Generally,

polyp arise from sub epithelial tissue . In colon cancer, polyp is arise from intestinal epithelium.



Polyp

can be either malignant or benign. The polyp in colon cancer is

Classification of Polyp Neoplostic

Adenomatous polyps are neoplastic by definition Precursor to colon cancer Subclassfied into dysplasia depending on the architechtural features; -high -low -medium High-gred dysplasia and adeno carcinoma and the main cause in most cancer cell

Non - neoplastic

The most commonly encounter in the colon are hyper plastic polyp Less risky and lower frequency in being malignant

Genetic Event in Colon Cancer



A model of Genetic Event in Cololectal Cancer.

Adenoma-Carcinoma Sequence Originally

proposed by Hill and in

1978 It is generally believed that almost all colorectal adenocarcinoma arise from adenomas. Specific chromosomal and somatic genetic changes during the transition from colonic to invasive carcinoma. 

A

PC gene  APC gene has been mapped to the tumor suppressor locus (5q21-q22) and it is thought to be involved in the initiation of adenoma formation

  Inactivation

of APC gene by 2 mutations is involved in the development of adenomas, and loss of heterozygosity of the APC gene is associated with the further progression to carcinoma.

  Mutation

in AOC gene is the most frequent genetic mutation seen in colon cancer cells.



K-

ras protooncogene This gene is thought to promote tumorigenesis by causing hyperproliferation of the colon cells, both at early adenoma stage and later at the time of malignant transformation.  DCC

gene Located in chromosome 18q and is a neural cell adhesion molecule. It may play role in tumor progression, invasion and metastatis.

p53

gene Located on chromosome p17 and involved in late malignant transformation, during the conversion from adenoma to focal carcinoma. Lost gene function is more common in carcinomas. Mutation of p53 mat have multiple effects - Decrease ability to detect DNA damage

 

Causes or factors for developing colorectal cancer

High fat diet intake. - A diet high in fat, especially animal fat, not only raises the risk factor of being overweight, it also increases risk factor for colon cancer. Have a mother, father, sister, or brother who developed colorectal cancer or polyps. - When more than one family member has had colorectal cancer, the risk to other members may be three-to-four times higher of developing the disease. This higher risk may be due to an inherited gene.



Have history of benign growths, such as polyps, that have been surgically removed. Age. Colon cancer is rare in those under 40 years. The rate of colorectal cancer detection begins to increase after age 40. Most colorectal cancer is diagnosed in those over 60 years.  

Stages of the Colon Cancer

Why colon cancer divided into many stages? Important

to indicate the extent of cancer within the body Staging needed to determine the likely outcome of cancer and treatment suitable to cure it. Useful way to identifying the extent of tumor-size, degree of growth and its ability to spread. 

Colon cancer stages categorized based on 3 criteria: 1)Tumor(T) depth 2)Evidence of lymph node(D) spread 3)Present or absent of metastases(M).

Stage 1 The

tumors are small and just start developing. The cancer is confined to the lining or muscular wall of the colon and yet spread anywhere else Less advance tumor Normally treated by surgery Have 90% of curability 

Stage 2 Cancer

have spread through muscular muscle of intestine and might as well extended to the adjacent organs through the structure but have not spread to the lymph node. Treated by surgery. Have 80% chances of cure.

Stage 3 Cancer

have spread outside the intestine to one or more lymph node near the bowel. Can be treated by surgery or chemotherapy. Have 60-70% chance of cure. 

Stage 4 The

cancer have spread beyond the colon to distant sites or organs, possibly including the liver or lungs. Only can be treated by chemotherapy. The chance of cure is rare.

Treatment for Colon Cancer 1. Surgical resection - Remove affected region

2. Chemotherapy - Chemical treatment - Kill off cancer cell - Keep the cell from dividing

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3. Radiation therapy - Before surgery- shrink the tumor - After surgery – prevent the tumor from coming back - Most common use- external radiation - Quick but frequent



Surgery

Surgery (removing

the cancer in an operation) is the most common treatment for all stages of colon cancer. There are 5 types of surgery that can be done to the patient that are: ◦ ◦ ◦ ◦ ◦

Local excision Resection Resection and colostomy Radiofrequency ablation cryosugery

Local excision If

the cancer is found at a very early stage, it may be remove without cutting through the abdominal wall. By putting a tube through the rectum into the colon and cut the cancer out. This is called a local excision. If the cancer is found in a polyp (a small bulging piece of tissue), the operation is called a polypectomy.

polyp

Resection If

the cancer is larger, perform a partial colectomy (removing the cancer and a small amount of healthy tissue around it). The doctor may then perform an anastomosis (sewing the healthy parts of the colon together). The doctor will also usually remove lymph nodes near the colon and examine them under a microscope to see whether they

       Colon

cancer surgery with anastomosis. Part of the colon containing the cancer and nearby healthy tissue is removed, and then the cut ends of the colon are joined.

Large polyp

Resection and colostomy  If

the doctor is not able to sew the 2 ends of the colon back together, a stoma(an opening) is made on the outside of the body for waste to pass through.  This procedure is called a colostomy.  A bag is placed around the stoma to collect the waste.  Sometimes the colostomy is needed only until the lower colon has healed, and then it can be reversed.  If the doctor needs to remove the entire

      

 Colon

cancer surgery with colostomy. Part of the colon containing the cancer and nearby healthy tissue is removed, a stoma is created, and a colostomy bag is attached to the stoma.

Radiofrequency ablation The

use of a special probe with tiny electrodes that kill cancer cells. Sometimes the probe is inserted directly through the skin and only local anesthesia is needed. In other cases, the probe is inserted through an incision in the abdomen. This is done in the hospital with general anesthesia.

Cryosugery A

treatment that uses an instrument to freeze and destroy abnormal tissue, such ascarcinoma in situ. Also called cryotherapy.

Side effect Surgery causes

short-term pain and tenderness in the area of the operation. Surgery for colorectal cancer may also cause temporary constipation or diarrhea. Patients who have a colostomy may have irritation of the skin around the stoma. 

 Chemotherapy  Affects

cancer cells and also normal

cells.  Side effects depend largely on the specific drugs and the dose (amount of drug given).  Common side effects of chemotherapy include: ◦ ◦ ◦ ◦ ◦ ◦

nausea and vomiting hair loss mouth sores Diarrhea Fatigue Less often, serious side effects may occur, such as infection or bleeding.

 Radiation

therapy  Also affects on cancer cells and normal cells.  Side effects of radiation therapy depend mainly on the treatment dose and the part of the body that is treated.  Common side effects of radiation therapy: ◦ Fatigue ◦ skin changes at the site where the treatment is given ◦ loss of appetite ◦ Nausea ◦ Diarrhea ◦ Sometimes, radiation therapy can cause

Prevention

Taking

non-steroidal antiinflammatory drugs(NSAids)- it protect against colon cancer development by inducing cell death or by inhibiting growth in colon cancer cell lines



Taking

high calcium diet may be protective – calcium may counteract the carcinogenic properties of high fat meat by binding free bile and fatty acids.

Other prevention on daily basis Eat

plenty of fruits and vegetables – for example five portions a day Diet low in animal fat Reduce red meat intake and replace with fish and poultry Moderate alcohol intake Avoid smoking Regular exercise Maintain a healthy weight

Seek

advice about the symptomsso , we can get early treatment and reduce the risk getting the colon cancer

References 

1. Bub et al. (2008) Colorectal Cancer 2nd Ed. Canada. Jones & Bartlett Publishing.

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2. Bub et al. (2003) About Colorectal Cancer. Canada. Jones & Bartlett Publishing.

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3. Holen & Chung (2008) Dx/Rx Colorectal Cancer. Canada. Jones & Bartlett Publishing.

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4. Edited by Swan (2005) Colorectal Cancer. London. Whurr Publishers.

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5. Vogelstein & Kinzler (2002) The Human Genetic Basis of Human Cancer 2nd Ed. New York. Mc-Graw Hill Medical Publishing Division.

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6. Dollinger et al. (1991) Everyone’s Guide to Cancer Therapy. U.S.A. A Somerville House Book.

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Edited by Saltz(2007) Colorectal Cancer Evidence-Based Chemotherapy