Left colonic cancers
Rectal cancers
Diagnosis
Staging of Colorectal Cancer
Treatment
Carcinoma of colon and rectum is the second most common cause of carcinoma deaths in the US. It starts to occur from 40 to 70 years of age. Right sided colonic cancers are more common in women and left sided colonic and rectal cancers are more common in men. Predisposing factors are family history of carcinoma of colon, familial colonic polyposis, regional enteritis and ulcerative colitis. Consumption of high fiber diet and taking aspirin daily may reduce incidence of colon cancer. Symptoms of cancer depend mainly on which side of the colon it is present. Right sided cancers tend to be insidious in onset and left sided colonic cancers present as disturbance in bowel habits.
Right colonic cancers: Cancers arising from caecum and ascending colon present late because of the late onset of symptoms. The colonic walls are thin and the bowel contents are liquid in nature here. So the cancer grows to a large size before the patient complains of any problem. But the growth continues to bleed so the patient may present with anemia and general debility. If the growth is large, it may be palpable through the abdominal wall. Pain is rarely a symptom. The lymph nodes and liver may also get involved before a diagnosis is made.
Left colonic cancers: Because the bowel contents are semi solid in the left side of colon and also because the colon is thick walled on the left side, carcinomas arising from left side of colon tend to obstruct the lumen and so present as subacute obstruction. Cancer of colon may be an ulcer, a cauliflower like growth, a constricting ring like growth or that arising from a polyp. The encircling constriction like cancer is the one to present as an obstruction first. Other types present as bleeding in stools. Symptoms of carcinoma of left colon are altered bowel habits with alternating episodes of constipation and diarrhoea. There may be distension of bowel proximal to the obstruction.
Rectal cancers: Carcinoma of rectum presents as passing blood and mucus in stools. There may be dyschezia (sensation of incomplete evacuation) and pain while passing motion. Dragging pain in the perineum and anal region indicate involvement of surrounding structures.
Diagnosis: Occult blood in stool is always present. Barium enema X rays may show the growth in 70% of the people. Colonoscopy with a flexible endoscope is necessary to diagnose carcinoma of colon and to take a biopsy for histopathological diagnosis. Sigmoidoscopy reveals cancers of rectum and sigmoid colon. Digital per rectal examination and proctoscopy are enough to diagnose rectal cancers. Blood tests show anemia, rise in ESR and an increase in carcino embryonic antigen. This test is more useful to assess the completeness of surgical resections and any recurrence of cancer later. Ultrasonography is done to ascertain the presence of liver secondaries.
TNM staging of Colorectal Cancer
TNM staging of colorectal cancer is done by assessing the extent of spread through the layers that form the wall of the colon and rectum. These layers, from the inner to the outer, include the mucosa, the muscularis mucosae, the submucosa, the muscularis propria, the subserosa, and the serosa. Though all these layers are not important in microscopic level, the outcome of treatment of carcinoma of colon and rectum depends on the extent of involvement of these layers.
Tx: Incomplete information.
Tis: The cancer is in the earliest stage. It has not grown beyond the mucosa (inner layer) of the colon or rectum. This stage is also known as carcinoma in situ.
T1: The cancer has grown through the mucosa and, the muscularis mucosae and infiltrates the submucosa.
T2: The cancer has involved the mucosa, the muscularis mucosae, the submucosa, and extends into the muscularis propria.
T3: The cancer has grown all the layers of the colon or rectum. It has spread to the subserosa and serosa but not to any neighboring organs or tissues.
T4: The cancer has spread through the wall of the colon or rectum into nearby tissues or organs.
N Categories for Colorectal Cancer.
N categories indicate whether or not the cancer has spread to regional lymph nodes and, if so, how many lymph nodes are involved.
Nx: Incomplete information regarding lymph node involvement.
N0: No lymph node involvement.
N1: Cancer cells involve 1 to 3 regional lymph nodes.
N2: Cancer cells involve 4 or more regional lymph nodes.
M stages for Colorectal Cancer.
M categories indicate whether or not the cancer has spread to distant organs like the liver, lungs or nonregional lymph nodes.
Mx: Incomplete information regarding distant metastasis.
M0: No distant spread.
M1: Distant spread is present.
Stage Grouping
Once a patient's T, N, and M involvement has been determined, this information is combined in a process called stage grouping to determine the stage, expressed in Roman numerals from stage I (the least advanced stage) to stage IV (the most advanced stage). The following table illustrates how TNM categories are grouped together into stages.
Stage 0: Tis, N0, M0
Stage I: T1, N0, M0 T2, N0, M0
Stage II: T3, N0, M0T4, N0, M0
Stage III: Any T, N1, M0 Any T, N2, M0
Stage IV: Any T, Any N, M1
A Simplified staging for carcinoma of colon and rectum (Duke's Classification).
Stage 0: The cancer is in the earliest stage. Only the Inner layer (mucosa) of the colon or rectum is involved. This stage is also known as carcinoma in situ.
Stage I: The cancer has grown through the mucosa and the next layer, the muscularis mucosae, and into the submucosa. It may also have grown into the muscularis propria, but it has not spread outside the wall itself into nearby tissue.
Stage II: The cancer has grown through the wall of the colon or rectum through the muscularis propria into nearby tissues. It has not yet spread to the nearby lymph nodes.
Stage III: The cancer has spread to nearby lymph nodes but it has not spread to other parts of the body.
Stage IV: Here the cancer has spread to distant organs such as the liver, lung, peritoneum or ovary.
Treatment: Most of the patients with carcinoma of colon are treated with surgical removal of the cancer and a large segment of affected colon and lymph nodes. Right sided colonic growths are treated with right hemicolectomy , transverse colon growths with transverse colectomy and left colonic growths with left hemicolectomy. Sigmoid colectomy alone may be sufficient for growths from sigmoid colon. Rectal cancers are dealt with according to the location of the cancer. Anterior resection, abdomino perineal resection, Hartman's procedure are all options for carcinoma of rectum. Most often a permanent or temporary colostomy is necessary.
For obstructing growths a temporary colostomy may be done to tide over the crisis and a definitive surgery is performed later. For inoperable obstructing carcinomas a colostomy is done to make the patient more comfortable and palliative chemotherapy with 5 fluro uracil is given. Very late stages of carcinoma colon with liver metastasis are treated with injection of chemotherapy agents directly into the hepatic artery.
Levamisole is given as empirical treatment to boost host immunity. All these measures improve quality of life but do not prolong it.