What is Colorectal Tumor?
Colorectal Tumor is cancer involving the colon (ascending colon, transverse colon, descending colon), rectum to the anus. It is one of the top leading cancer involving both men and women. Internationally, more than 1 million people are diagnosed with colorectal tumor every year. When detected early and treated in early stages, the prognosis is good.
Colorectal cancer is mostly adenocarcinomas. Other rarer cancers involving the colon are carcinoid tumors, melanomas, lymphomas and sarcomas. Most colorectal cancers derived from small noncancerous adenomatous polyps which may turn cancerous with time. If the polyps are greater than 1 cm, has villous features or has high grade dysplasia, the chance of malignancy (cancer) increases. Hence when detected and removed early, risk of colorectal cancer decreases.
75% of colon cancer patients have no known predisposing factors. So what leads to the development of colorectal tumor?
1. About 85% of sporadic colon cancer arises from noncancerous benign polyps which look like mushrooms found on the lining of the colon. There is a loss of tumor suppressor genes and activation of oncogenes which leads to malignant transformation of normal cells to cancerous cells.
2. About 10-20 % of colon cancers arise from serrated polyps which involves the inactivation of DNA mismatch repair gene MLH1which eventually activates the mutations of BRAF gene. These mutations in turn lead to cancerous transformation of cells.
3. 5 % of colon cancers arise from inherited germline mutations resulting in Familial Adenomatosis Polyposis (FAP), Lynch Syndrome and Hereditary NonPolyposis Colorectal Cancer (HNPCC). These hereditary syndromes results in thousands of polyps lining the colon and rectum which increase one’s risk of colorectal tumor. These syndromes are detectable through genetic testing. Colorectal screenings for these patients are highly recommended.
Risk factors of developing colorectal tumor
1. Age: The incidence of colon cancer increase sharply after age 45. 90% of cancer patients are diagnosed at age 50 and above.
2. Family History of Colon Cancer or polyps: If your first degree family members (child, siblings or parents) have colon cancer, your risk of colon cancer is 2 times more than general population. Your risk increased to 4 fold if your family member is diagnosed at < 45 years of age. Your lifetime risk of colon cancer is about 25-50% if more than one family member has the disease.
3. Inflammatory Bowel Disease: Chronic inflammatory disease of the colon such as ulcerative colitis and Crohn’s disease increases your risk of colon cancer. The risk begins to rise after 7-10 years after the disease onset and continues to rise as the disease progresses.
4. Race: African- Americans are at higher risk as compared to other races.
5. Personal history of colon cancer or polyps: If you have a history of colon cancer or polyps, the risk of recurrence is higher.
6. Inherited Syndromes: Familial Adenomatous Polyposis (FAP) and Hereditary NonPolyposis Colorectal Cancer also known as Lynch syndrome puts you at higher risk of colorectal tumor. Genetic Screening and colorectal cancer screening is advisable for families with these syndromes.
7. Diet and Lifestyle activities: Diet rich in fats and red meats and low in fiber is associated with increased risk of colorectal cancer. Smoking and alcohol intake, sedentary lifestyle, pre-existing diabetes and obesity also put you at higher risk of colorectal tumor.
8. Previous radiotherapy: Previous radiation therapy targeted at the abdomen for previous cancer treatment also increases the risk of developing of colorectal cancer.
The symptoms of colon cancer depend on its location and whether it has metastasis (spread).
1. Fatigue and weakness which is the result of chronic blood loss which leads to iron deficiency anemia.
2. Change in bowel habits: These include changes in stool frequency, stool consistency or constipation alternating with diarrhea.
3. Per rectal bleeding: Blood stained stools or passing out frank blood during defecation.
4. Abdomen pain will occur when there is severe obstruction and maybe accompanied with abdomen distension, vomiting and constipation.
5. Unintentional weight loss
6. Tenesmus : Feeling of incomplete emptying of stools
Right sided colon cancer usually causes chronic blood loss resulting in anemia hence patients will feel fatigue. Obstruction is less likely due to the larger diameter of the colon.
Left sided colon being smaller in diameter will often cause obstruction symptoms like abdomen pain, constipation alternating with diarrhea and blood stained stools.
Rectal tumors will result in patients experiencing tenesmus, urgency and recurrent bleeding per rectal.
Anal tumors may present as an external mass, ulcers, and polyps or as an internal mass. Rectal bleeding may be inconsistent. Pain is usually absent.
Physical clinical findings
The doctor will do a physical examination of your abdomen and a digital examination of your rectum. If the cancer is in advance stages, there may be a mass upon palpation of your abdomen as well as area of tenderness. The liver maybe enlarged if the tumor has spread to the liver. Digital examination through the anus will determine if there is any mass at the distal rectum, blood in stools and also whether the anal sphincter and pelvic floor is involved.
Investigations to confirm diagnosis
1. Blood tests
2. Fecal testing
3. Colonoscopy: It is a diagnostic procedure whereby a tube with a video camera is inserted through your anus upwards to visualize the whole colon. If a polyp is seen, biopsy of the polyp and removal can be done during this procedure.
4. Barium enema: Barium a contrast dye is given to a patient via enema form and is captured by x-ray to visualize the entire colon including the caecum which may not be reachable at times by colonoscopy.
Staging of colorectal tumor
The TNM system is used to classify and stage colon cancer. It depends on the Tumor invasion depth into the wall of colon, the number of lymphNodes the cancer has spread to and lastly Metastasis whether the cancer has spread to other organs.
Staging is important as it correlates with patient’s long term survival. It also help the physician decide the management plan and also if pre-operative chemoradiotherapy is necessary to shrink the tumor before operation. It also determines if patient require adjuvant therapy like chemotherapy or radiotherapy.
Stage 0: The tumor is in very early stage and only involves the innermost layer of the colon. Also known as carcinoma in situ.
Stage 1: The tumor has grown through the mucosa colon wall (superficial lining) but has not invaded into the wall.
Stage 2: The tumor has invaded through the colon wall but has not spread to any lymph nodes.
Stage 3: The tumor has invaded through the colon wall and has spread to lymph nodes.
Stage 4: The tumor has spread beyond the colon to other organs such as liver and lungs.
The treatment for colorectal tumor depends on the stage of the cancer.
1. Surgery: Colectomy which means resection of the primary colon or rectal cancer and also the involved lymph nodes is the treatment of choice for localized colon cancer stage 1-3. For stage 4 colorectal tumors where the cancer has spread to other organs, surgery is usually palliative to relieve symptoms such as intestinal obstruction, bleeding and pain. The treatment of choice for such advanced disease is usually systemic chemotherapy.
As medicine advances, colectomy may be done with laparoscopy which is less invasive and speed up recovery as compared with previous open colectomy.
In some patients, a colostomy which is a bag connected to a section of the colon (stoma) that is brought to an opening in the abdomen may be necessary to divert the body wastes while waiting for the operated site of the colon to heal. Most of the time this is temporary however if the cancer involves the rectum outlet it may be permanent.
2. Chemotherapy: Adjuvant Chemotherapy which is post operation chemotherapy is standard treatment for patients with Stage 3 colon cancer and also in some patients with stage 2 colon cancer. Chemotherapy drugs commonly used are fluorouracil in combination with other drugs such as levamisole and leucovorin. These drugs are used to kill the remnant cancer cells and to relieve symptoms. If the colorectal tumor is too large to operate, chemotherapy may be given prior to operation to shrink the tumor first. This is known as neo-adjuvant chemotherapy. Medical Oncologist will decide the chemotherapy regime and frequency.
3. Biologic Agents: Monoclonal antibodies such as cetuximab (Erbitux), panitumumab (Vectibix), bevacizumab (Avastin) are anti-angiogenesis drugs that act on specific defects that allow cancer cells to proliferate. They can be given alone or together with chemotherapy. They are reserved for people with very advanced stage of colon cancer.
4. Radiation therapy: It is standard treatment for patients with rectal cancer. Role of radiation therapy in colon cancer patients is limited. However it is sometimes used with chemotherapy to shrink large tumors before operation. Radiation uses powerful energy sources like x-rays to kill cancer cells. It is also useful if cancer cells have spread to the bone and brain.
5. Treatment options if cancer has spread to liver: Radiofrequency Ablation of the liver lesion (burning the cancer), surgical resection of the tumor, cryotherapy (freezing the tumor) or chemotherapy and radiation therapy targeted at the liver.
The stage of the cancer at presentation is important determining factor of long term survival. 5 year survival rate means the percentage of patients that survive at least 5 years after diagnosis.
Stage 1: > 90%
Stage 2: 70-85%
Stage 3: with less than 4 positive lymph nodes: 67%
Stage 3: with more than 4 positive lymph nodes: 33 %
Stage 4: 5-7% due to cancer having spread to other organs
At each stage, cancer of the rectum has poorer outcomes.
Prevention of colorectal cancers
1. Colorectal cancer screening has proven to save lives and reduce mortality. This is because detection of early stages of cancer with improved treatment as well as prevention by removing polyps has deterred cancers being diagnosed at a later stage which has poorer outcomes.
The screening tests recommended depend on the risk an individual has in developing in cancer. It will be covered in greater details in the next page.
2. Dietary and Lifestyle changes:
3. Medications like aspirin, Nsaids and Celebrex: Some studies have found that these drugs may reduce the risk of colorectal cancer. However they do carry increased risk of gastrointestinal bleeding, stomach ulcers and heart problems (especially in COX2 inhibitors). The risks and benefits must be weighed and discussed with your doctor before taking such medications.
4. Surgery: In patients with inherited conditions like Familial Adenomatosis polyposis, Hereditary NonPolyposis Colorectal Cancer and inflammatory bowel disease like Ulcerative Colitis, the risk of developing cancer is many times higher than a normal person. Hence, your doctor may recommend prophylactic surgical removal of the whole colon and rectum to prevent cancer to develop.
After having discussed all about colorectal tumors, you should know there are some conditions that may present similarly to the symptoms of colorectal cancer. The conditions include:
1. Irritable Bowel Disease
2. Diverticular disease
3. Ischemic Colitis
4. Inflammatory Bowel Disease
5. Infectious Colitis
7. Carcinoid tumors
8. Arteriovenous Malformation (AVM)
9. Gastrointestinal lymphoma
In conclusion, if you have symptoms suggestive of colorectal tumor, do seek a doctor’s advice and carry out the necessary tests to determine the actual cause. It could be any of the above conditions instead of the cancer. Also lead a healthy lifestyle balanced with the right diet and adequate amount of exercise as general prevention of cancer.