Colorectal cancer, commonly referred to as colon cancer, is an abnormal pattern of growth of cells that invade and destroy the health surrounding tissue and may spread to distant sites. Cancer is life-threatening and early diagnosis, rapid treatment and proper monitoring is therefore essential. Malignant tumors may arise anywhere in the body and sometimes this spreads to the colon and rectum in which case it is known as a secondary tumor or metastases. If the tumor originates within the colon and rectum, then it is known as a primary tumor. Colorectal cancer is a very common types of cancer and a person with risk factors, like a family history of colorectal cancer, needs to be tested regularly.
Diagnosis of Colorectal Cancer
Screening tests are an effective means to identify cancer in the early stages and commencing treatment immediately. Early detection greatly increases the chances of survival. Annual screening tests should be conducted on a person who is considered high risk. These tests may include :
- Faecal occult blood test (FOBT) which can detect small amounts of blood present in stools.
- Sigmoidoscopy where the lower part of colon and rectum can be visualized for any polyps and abnormal growths through the use of a miniature video camera on a flexible tube.
- Colonoscopy where the whole colon with rectum can be visualized with a long lighted tube.
- Double contrast barium enema which highlights polyps or other growths on an X-ray or CT scan.
- Digital rectal exam (DRE) is part of a physical examination in which the doctor puts a gloved hand in the rectum to feel for any abnormal growth.
If the above tests reveal an abnormal growth like polyp or tumor, then the mass needs to be biopsied to examine it under a microscope. A pathologist can then determine the type of growth, whether benign or malignant, or if malignant then the stage of cancer. This greatly assists with determining the approach to treatment.
Stages of Colorectal Cancer
- Stage 0 : Carcinoma in situ where the cancer is limited to the innermost lining of the colon and rectum.
- Stage 1 : Cancer has progressed into inner layers of the colon and rectum but has not extended through the wall.
- Stage 2 : Cancer has spread more deeply into or through the wall extending to the local tissue but has not reached the lymph nodes as yet.
- Stage 3 : Cancer has spread to the lymph nodes but not to other organs of the body.
- Stage 4 : Metastasis (spread) to other organs such as liver and lungs.
Treatment of Colorectal Cancer
There are two types of cancer therapy- local therapy and systemic therapy.
Local therapy involves removing or destroying the cancer near the colon or rectum. The two main modalities of treatment in local therapy are surgery and radiotherapy (radiation).
Systemic therapy involves treatment with the use of drugs that enter the bloodstream and act on the tumor tissues throughout the body. It includes chemotherapy (cancer killing drugs) and biological therapy agents.
The most common mode of treatment is surgery and the cancerous tissues can be approached by following ways-
- Open surgery
After the tumor has been removed surgically, the tissue is send for biopsy and the lymph nodes are also examined and biopsied for evidence of local spread or metastasis. The affect part of the colon or rectum is removed and the healthy two ends are then surgically reconnected. When this is not possible due to excessive removal of tissue, then one end of the bowel is connected to an opening the abdominal wall (stoma). This type of operation is called a colostomy in which a bag is connected with the stoma to collect the waste matter.
- Stage 0 and stage 1 are managed with local surgical excision of the cancerous tissue. No additional treatment may be necessary for these stages of cancer.
- In stage 2 cancer, surgery is the main approach but in cases with risk of recurrence or a positive family history then additional adjuvant chemotherapy is also implemented.
- Stage 3 cancers are primarily treated with surgery (partial colectomy) followed by adjuvant chemotherapy.
- Stage 4 cases are unlikely to cure the cancer but surgery can help to ease symptoms and improve the quality of life. Chemotherapy is almost always indicated in these cases.