Colorectal Cancers

These tumors arising from the large intestine are one of the most common cancers worldwide. They are the second most leading cause of cancer related deaths among women and third most common in men. The inner lining of the intestine called as mucosa, being in constant contact with the food we eat, is most prone for cancers. The risk factors for these tumors can be broadly classified into three categories.

• Genetic/ Hereditary: The genetic/ inherited conditions which run in families include HNPCC (Hereditary non polyposis colorectal cancer) and FAP (familial adenomatous polyposis). Patients with strong family history of colorectal or uterine cancers, especially relatated to people who developed these tumours at a younger age and those who have multiple relatives affected by these cancers should undergo regular screening.
• Environmental: The second risk factor includes environmental/ dietary which include smoking, inadequate dietary fiber, excessive consumption of red meat and food additives. Colon being the last portion of the intestine where the undigested food materials get concentrated is exposed to the highest concentration of these carcinogenic chemicals.
• Predisposing Diseases: The third category include patients with pre-existing colonic diseases like inflammatory bowel disease and polyposis which increase the risk of tumors. Current recommendations advice screening from the age of 45 years in normal people and earlier in people with above risk factors.

Early symptoms include change in bowel habits, bleeding in the stools, abdominal or perianal pain, loss of weight and unexplained anaemia. Depending on the clinical suspicion, these tumors can be diagnosed based on colonoscopy. Evaluation also includes either CECT or a PET scan for assessing the extent of the disease.

Colorectal cancer starts in the colon or the rectum. These cancers can also be called colon cancer or rectal cancer, depending on where they start.

Since these are very common tumors, universal screening is recommended. All patients above 45 years need screening. People in high risk groups should start getting screened even earlier based on their risk factors. Colonoscopy is the most accurate screening test and is recommended once in 10 years for average risk patients and every 5 years for high risk patients. Faecal occult blood test done yearly is the non invasive option for low risk patients for follow up after initial screening colonoscopy.

Treatment and outcome depend on the site of the tumor, stage and the nature of the tumors. Surgery followed by chemotherapy is offered for early tumors. Patients with advanced tumors benefit from down-staging by neoadjuvant chemo-radiation prior to surgery. Princples of surgery involves removal of the affected segment of large intestine along with its lymphatics for adequate microscopic clearance. Depending on the location, this can be right or left hemicolectomy, sigmoid colectomy and anterior resection of the rectum. Patients with very low rectal tumors involving anal canal may need abdominoperineal resection. All the above can be performed laparoscopically for faster recovery. Patients with very low rectal tumors or those presenting for emergency surgery may need a temporary colostomy for enhanced safety.

Other less common tumors of the large intestine include GIST, intestinal lymphomas and sarcomas. The treatment of these tumors is also primarily surgical but needs to be individualized.