Colorectal cancer, also known as bowel cancer or colorectal cancer or cancer of the bowel, is the cancer of large intestine (lower part of the digestive system). Majority of colorectal cancer cases start as small and non-cancerous clumps of the cells known as adenomatous. After a certain period of time, these polyps become colorectal cancers.
Types of Colorectal Cancer
Adenocarcinoma is considered as the most common type of colorectal cancer. This type of colorectal cancer begins in the inner layer that spreads deep into the other layers. Adenocarcinoma can be further categorized into two subtypes that include –
- Signet Ring Cell Adenocarcinoma
- Mucinous Adenocarcinoma
Other Types of Colorectal Cancer
Gastrointestinal Stromal Tumors : This is considered as a rare type of colorectal cancer that begins in a cell found in the gastrointestinal tract lining known as interstitial cells of Cajal (ICCs). These type of tumors are classified as sarcomas that include cartilage, fat, bones, blood vessels, deep skin tissues, muscle and nerves.
Squamous Cell Carcinomas: Certain portions of the gastrointestinal tract such as the end of the anus and the upper part of the esophagus are lined with squamous cells. Squamous cell carcinomas are those cancers that begin in these cells.
Leiomyosarcomas: This type of cancer typically means- cancer of smooth muscle. This is considered as a rare type that account for only 0.1% of all colorectal cancer cases.
Gastrointestinal Carcinoid Tumors: This type of colorectal cancer is considered as a slow-growing cancer that develops in the neuroendocrine cell in the GI tract lining.
Melanomas: This type is primarily related with skin but can also happen anywhere that include recturm or colorectal.
Primary Colorectal Lymphomas: The cancers that grow in the lymphatic system of cells (lymphocytes) are known as lymphomas. Primary colorectal lymphomas develop in the later stages of life and are more commonly seen in men as compared to women.
The uncontrollable growth of cells that do not die causes cancer. There is a normal cycle of growth, division and death in case of normal cells but colorectal cancer do not experiences this type of normal cycle and continue to grow and divide. There are no as such known causes of colorectal cancer.
Symptoms of Colorectal Cancer
The early symptoms of colorectal cancer include –
- Unexplained weight loss
- Bleeding from the rectum or blood in the stools
- Abdominal pain
- Change in normal bowel habits that continue for more than 3 weeks including passing of stools more frequently, diarrhea or constipation
Sometimes bleeding happens when the colorectal cancer progresses. Gradually, there will be not enough red blood cells in the body that is called as anemia. Following are some of the symptoms of anemia –
Also obstruction is caused by the colorectal cancer that include following symptoms –
- A feeling of bloating, especially near the belly button
- Abdominal pain
Tests used to diagnose colorectal cancer include the following:
- Physical examination and History: An examination of the body to check general signs of health, including checking for signs of disease, such as lumps or anything else that seems unusual. A history of the patient's health habits and past illnesses and treatments will also be taken.
- Digital rectal exam (DRE): An exam of the rectum. The Oncologist or nurse inserts a lubricated, gloved finger into the lower part of the rectum to feel for lumps or anything else that seems unusual. In women, the vagina may also be examined.
- Proctoscopy: An exam of the rectum using a proctoscope, inserted into the rectum. A proctoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove tissue to be checked under a microscope for signs of disease.
- Colonoscopy: A procedure to look inside the rectum and colon for polyps (small pieces of bulging tissue), abnormal areas, or cancer. A colonoscope is a thin, tube-like instrument with a light and a lens for viewing. It may also have a tool to remove polyps or tissue samples, which are checked under a microscope for signs of cancer.
- Biopsy: The removal of cells or tissues so they can be viewed under a microscope to check for signs of cancer. Tumor tissue that is removed during the biopsy may be checked to see if the patient is likely to have the gene mutation that causes HNPCC. This may help to plan treatment. The following tests may be used:
- Reverse-transcription polymerase chain reaction (RT-PCR) test: A laboratory test in which cells in a sample of tissue are studied using chemicals to look for certain changes in the structure or function of genes.
- Immunohistochemistry study: A laboratory test in which a substance such as an antibody, dye, or radioisotope is added to a sample of tissue to test for certain antigens. This type of study is used to tell the difference between different types of cancer.
- Carcinoembryonic antigen (CEA) assay: A test that measures the level of CEA in the blood. CEA is released into the bloodstream from both cancer cells and normal cells. When found in higher than normal amounts, it can be a sign of rectal cancer or other conditions
After Colorectal cancer has been diagnosed, tests are done to find out if cancer cells have spread within the Colon and rectum or to other parts of the body.
The process used to find out whether cancer has spread within the colon and rectum or to other parts of the body is called staging. The information gathered from the staging process determines the stage of the disease. It is important to know the stage in order to plan treatment. The following tests and procedures may be used in the staging process:
- Chest x-ray
- CT scan
- MRI (magnetic resonance imaging)
- Endoscopic ultrasound (EUS)
- PET scan (positron emission tomography scan)
- Carcinoembryonic antigen (CEA) assay
Tumour Board Evaluation
In the tumor board various specialists (Surgical Oncologists, Medical Oncologists, Radiation Oncologists, Urologists, Oncopathologists, Radiologists and Microbiologists) evaluate and discuss the findings, and chart out the optimal plan of treatment for each patient based on established national and international guidelines and protocols.
Surgery is the mainstay of treatment and involves in block removal of diseased segment with adequate margins, surrounding tissue and lymph nodes. The names given to such resections are right hemicolectomy, transverse colectomy, left hemicolectomy, sigmoid colectomy, and subtotal colectomy.
- Polypectomy: If the cancer is found in a polyp (a small piece of bulging tissue), the polyp is often removed during a colonoscopy.
- Local excision: If the cancer is found on the inside surface of the rectum and has not spread into the wall of the rectum, the cancer and a small amount of surrounding healthy tissue is removed.
- Resection: If the cancer has spread into the wall of the rectum, the section of the rectum with cancer and nearby healthy tissue is removed. Sometimes the tissue between the rectum and the abdominal wall is also removed. The lymph nodes near the rectum are removed and checked under a microscope for signs of cancer.
- Pelvic exenteration: If the cancer has spread to other organs near the rectum, the lower colon, rectum, and bladder are removed. In women, the cervix, vagina, ovaries, and nearby lymph nodes may be removed. In men, the prostate may be removed. Artificial openings (stoma) are made for urine and stool to flow from the body to a collection bag.
Radiation therapy or chemotherapy may be given before surgery to shrink the tumor, make it easier to remove the cancer, and lessen problems with bowel control after surgery. Treatment given before surgery is called neoadjuvant therapy. Even if all the cancer that can be seen at the time of the operation is removed, some patients may be given radiation therapy or chemotherapy after surgery to kill any cancer cells that are left. Treatment given after the surgery, to lower the risk that the cancer will come back, is called adjuvant therapy.
Radiation therapy is a cancer treatment that uses high-energy beams or other types of radiation to kill cancer cells. There are two types of radiation therapy. External radiation therapy uses linear accelerators outside the body to send radiation toward the cancer. Internal radiation therapy (Brachytherapy) uses a radioactive substance sealed in needles, seeds, wires, or catheters that are placed directly into or near the cancer. The way the radiation therapy is given depends on the type and stage of the cancer being treated.
Chemotherapy is a cancer treatment that uses drugs to stop the growth of cancer cells, either by killing the cells or by stopping the cells from dividing. When chemotherapy is taken by mouth or injected into a vein or muscle, the drugs enter the bloodstream and can reach cancer cells throughout the body (systemic chemotherapy). When chemotherapy is placed directly in the cerebrospinal fluid, an organ, or a body cavity such as the abdomen, the drugs mainly affect cancer cells in those areas (regional chemotherapy). The way the chemotherapy is given depends on the type and stage of the cancer being treated.
OTHER TYPES OF TREATMENT
Targeted therapy is a type of treatment that uses drugs or other substances to identify and attack specific cancer cells without harming normal cells. Monoclonal antibody therapy is a type of targeted therapy being studied in the treatment of rectal cancer.
Monoclonal antibody therapy uses antibodies made in the laboratory from a single type of immune system cell. These antibodies can identify substances on cancer cells or normal substances that may help cancer cells grow. The antibodies attach to the substances and kill the cancer cells, block their growth, or keep them from spreading. Monoclonal antibodies are given by infusion. They may be used alone or to carry drugs, toxins, or radioactive material directly to cancer cells. At DHRC, Colorectal cancers are routinely tested for men targets to be able to select specific targeted therapy for the patient.