Colon And Rectal Cancer
COLON AND RECTAL CANCER
Cancers of the colon and rectum are the commonest cancers of humankind. Several factors contribute to their high mortality–their internal location makes early detection difficult, and social values and personal factors make public awareness and screening efforts somewhat difficult. Yet current methods of screening would cut the mortality of these diseases considerably if only the medical and lay community would institute them regularly.
The colon and rectum are exposed to a wide variety of metabolic and environmental toxins ingested and excreted daily. Furthermore, the bacteria within the intestinal tract produce additional chemicals of their own. It is likely that some of this myriad of substances is cancer-causing in susceptible individual. A low fiber diet allows these chemical to come into contact with the inner wall of the colon and rectum for longer periods of time than a high fiber diet, and fiber may chemically neutralize some of these substances. Thus this dietary factor has been theorized to play a role in some populations as well. The specific cause of this cancer must nonetheless be considered unknown.
Some 60,000 deaths occur annually in the U.S. from this cancer, a high percentage of which could be avoided with appropriate screening and follow-up programs
SYMPTOMS
By the time a colon or rectal cancer causes symptoms it is frequently advanced beyond hope for a cure, although this is not always the case. Frequent symptoms include altered bowel habits or bloody stools, abdominal pain or fullness, a lump in the abdomen, weight loss and fatigue. Sometimes bleeding causes anemia which can in turn lead to lightheadedness, pale skin, and other symptoms.
Screening
A major goal is to detect the disease in the very earliest stages, or even in the pre- malignant phase. This refers to the detection of certain types of benign colon polyps which might later degenerate into cancer. Screening measures include testing several stool samples for microscopic amounts of blood using a special card test. This is advised periodically after age 40. A rectal exam by the physician also becomes important at that age in both sexes. After age fifty, proctosigmoidoscopy (“procto”) becomes equally important, this being examination of the lower colon through a viewing instrument; recently smaller flexible instruments have made this a much less uncomfortable and a more sensitive exam than it was just a few years ago. Barium enema colon x-ray is another exam used for diagnosis, but not generally in a screening setting.
Certain patients are at higher risk for colon cancer, including those with a familial form of colon polyps, ulcerative colitis, and a very strong family history of this type of cancer. Even more vigorous screening is called for in this setting. Although the screening recommendations are applicable to general populations, variations on them are common and the advice of the patient’s personal physician should be sought.
DIAGNOSIS
Once one or more of the tests above shows an abnormality, additional tests may include biopsy of any polyps or tumors. This may be done through a colonoscope (a longer version of the procto instrument) in some cases. If the tumor is large or if blockage appears imminent, an operation may be necessary. Depending on the location and extent of the tumor, the colon may be repaired to its normal state. In other cases a temporary or permanent drainage opening in the abdomen may be necessary (a colostomy).
Blood tests, x-rays, and scans may reveal evidence of tumor spread at the time of diagnosis, and at least preliminary evaluation should be done to evaluate the extent of spread.
TREATMENT
Surgery as mentioned above is the primary means of treatment. In the case of polyps or very early cancers, this may be curative, and even in other cases is often beneficial since blockage of the colon is inevitable in other cases at some point.
Cancers low in the rectum may be approachable and occasionally even curable by special radiation techniques. This may not be available or advisable in many cases, but is worth considering for some.
Chemotherapy has been disappointing both as a curative and even as a palliative measure to reduce symptoms. Some patients derive temporary reduction in the tumor and metastases, but this usually does not last long enough to be meaningful for most. At present the role of chemotherapy in colon and rectal cancer must be considered limited.
PROGNOSIS
Five year survival data for colon cancer vary from around 70% for early cancers confined to the lining of the intestine to less than 10% when the tumor has already spread to the nearby lymph nodes. If distant spread has already occurred at the time of diagnosis, long-term survival should not be anticipated.
SUMMARY
It is worth emphasizing that the means to improve the detection of and survival for this disease is already available in the form of screening tests as discussed. The minor inconvenience, cost, and discomfort of the measures described, and the social reluctance to address issues pertaining to the rectum are killing many people each year. Every effort should be made to overcome these factors given the dismal and worsening statistics for cancer of the colon and rectum.