The incidence of rectal cancer in India is lower than that in the western countries, and it is the tenth leading cancer in India 
Mean age of rectal cancer (RC): around 40-45 yr.
Risk factors you cannot change (non-modifiable risk factors)
If you have had colorectal cancer earlier, you are more prone to develop new cancers in other areas of the colon and rectum even if the previous cancer was completely removed. The chances are greater if you had your first colorectal cancer at a younger age.
Risk factors you can change (Modifiable risk factors)
Cooking meats at very high heat (frying, broiling, or grilling) can create chemicals that might increase cancer risk. Diets high in vegetables, fruits, and whole grains have been linked with a lower risk of colorectal cancer, but fiber supplements have not been shown to help.
Signs and Symptoms
Most people with colorectal cancer do not experience any symptoms or have only non-specific symptoms in the early stages. When the symptoms appear, they vary depending upon the size and location of tumor in the intestine.
Screening and Diagnosis
Screening for Colorectal Cancer
Regular screening can help in early detection of colorectal cancer, when it is likely to be curable. In addition, some polyps can be detected and removed before they turn into colorectal cancer.
The various tests recommended to be used in screening for colorectal cancer include:
Screening is recommended for high-risk individuals, i.e. those with a close relative having colorectal cancer or polyps or patients having inflammatory bowel disease or patients with an inherited syndrome that increase the risk of colorectal cancer. FOBT should be done every 1-2 years, flexible sigmoidoscopy every 5 years and colonoscopy every 10 years in high-risk individuals.
Diagnosis of Colorectal Cancer
The symptoms of colorectal cancer usually appear only with advanced disease. If your doctor finds something suspicious in screening or you have any of the symptoms of colorectal cancer, further tests will be required to diagnose the condition.
History & Physical Examination:
In case you have any of the signs or symptoms suggesting colorectal cancer, the doctor will take complete medical history for presence of risk factors, including your family history.
During general physical examination, the doctor will palpate your abdomen for palpable masses or enlarged organs. A digital rectal examination (DRE) may also be performed. In this test, a gloved and lubricated finger is inserted into the rectum to feel for any abnormal areas.
These tumor markers cannot be used for screening of colorectal cancer because elevation of their levels doesn’t tell for sure that the person has cancer. The levels of these markers can sometimes be raised in benign conditions as well.
This is the most commonly used test to diagnose colorectal cancer if the symptoms are highly suggestive. It allows the doctor to look at the entire length of the colon and rectum using a colonoscope which is a thin flexible lighted tube with camera at the end attached to a monitor on the doctor’s desk. It is inserted through the anus and the camera allows the doctor to closely examine the inside of the colon through the images on the monitor. The colonoscope can also be used to insert special instruments to take a biopsy of suspicious-looking area or to remove polyps.
The test can be done on an outpatient basis in a hospital or doctor’s clinic. Before the test, certain instructions are given to make colon and rectum empty of food residue by a laxative and/or enema. These instructions should be understood well and followed perfectly. Colonoscopy is generally performed under mild sedation. The procedure is quite safe, though uncomfortable. Sometimes, you may have bloating, gas pains or cramping since air is pumped into the colon for better visualization. If a biopsy has been taken or polyp removed, you may have blood in stool for 1-2 days after the test.
Tissue biopsy is taken during colonoscopy from any suspicious area. A small piece of tissue is removed with a special instrument passed through the scope. The sample is sent to pathology lab for testing by a pathologist who looks for cancer cells in the specimen.
Genetic tests may also be done on the biopsy specimens to identify specific gene changes in the cancer cells. These tests are available at very few centres in the country.
Stages of Colorectal Cancer
Stage 0 or Carcinoma in situ: Abnormal cells are found in the innermost lining of the colon or rectal wall (mucosa).
Stage I: In this stage, cancer has formed in the mucosa (innermost layer) and has spread to the submucosa (layer of tissue under the mucosa) and muscle layer of colon or rectum. It has not spread into nearby tissue or lymph nodes
Stage II: The cancer has grown through the wall of the colon or rectum to the lining of the abdomen, called the visceral peritoneum and has grown into nearby structures. It has not spread to the nearby lymph nodes or elsewhere.
Stage III: The cancer has grown through the inner lining or into the muscle layers of the intestine and spread to lymph nodes, but not to other distant parts of the body
Stage IV: The cancer has spread to a distant part of the body, such as the liver or lungs.
Treatment of Colorectal cancer
Different modalities to treat colorectal cancer include:
These are used alone or in combination depending on the stage of the cancer, performance status of the patient, grade of the tumor and other factors.
Stage-wise treatment of colorectal cancer:
Treatment of colorectal cancer depends on the stage of the cancer.
Stage 0 colon/rectal cancer
Removal of a polyp which is called polypectomy, during the colonoscopy procedure is the treatment at this stage. If the polyp is not excised completely, additional surgery may be required. Rarely removing a part of the colon which is called partial colectomy may be required if a tumor is too big to be removed by local excision.
Stage I colon/rectal cancer
Surgical removal of the tumor and lymph nodes is usually the only treatment needed.
Partial colectomy- surgery to remove the section of colon that has cancer and nearby lymph nodes is the standard treatment. Additional treatment is usually not required.
Stage II colon/rectal cancer
Partial colectomy -surgery to remove the section of colon that has cancer and nearby lymph nodes is the standard treatment. Additional treatment in the form of chemotherapy or radiotherapy is indicated in certain conditions like: high grade tumor, high CEA (carcinoembryonic antigen) levels >5 ng/ml, if fewer than 12 lymph nodes are removed and examined and if the tumor had caused obstruction or perforation of the colon before surgery.
The various chemotherapy regimens used in treatment of colorectal cancer are given below.
Stage III colon/rectal cancer
Treatment usually involves surgical removal of the tumor followed by adjuvant chemotherapy. Patients with rectal cancer, radiation therapy may be used along with chemotherapy before or after surgery along with adjuvant chemotherapy.
Stage IV colon cancer
In this stage, surgery is not possible in majority of the cases considering the metastasis of the disease. However if the size of the metastasis is small and is excisable, surgery may be planned in such cases at the discretion of the surgeon.
Operations such as diverting colostomy may be required in patients with obstructed colon or perforated colon. In this procedure, the colon is cut above the level of the cancer and the end is attached to an opening in the skin on the abdomen to allow waste out.
CHEMOTHERAPY REGIMENS USED IN COLORECTAL CANCER
Some common treatment regimens include:
TARGETED THERAPY IN THE TREATMENT OF COLORECTAL CANCER
Targeted therapy targets the cancer’s specific genes, proteins, or the tissue environment that contributes to cancer growth and survival. Targeted therapy blocks the growth and spread of cancer cells while limiting damage to healthy cells.
It acts by stopping angiogenesis, which is the process of making new blood vessels. Few examples in this group include Bevacizumab, Ziv-aflibercept, Ramucirumab etc.
It acts by inhibiting the epidermal growth factor receptor. This may be effective for stopping or slowing the growth of colorectal cancer. Cetuximab, Panitumumab belong to this group of targeted therapy.
 Three-years report of Population Based Cancer Registries 2006-2008 (Detailed Tabulations of Individual Registries Data). National Cancer Registry Programme (Indian Council of Medical Research), Bangalore November 2010. Available from: http://www.PBCR_2006_2008.aspx, (accessed on December 27, 2012)