Colorectal Cancer

Synonyms

4

Overview

The rectum is the portion of the large bowel that lies in the pelvis, terminating at the anus. Cancer of the rectum is the disease characterized by the development of malignant cells in the lining or epithelium of the rectum. Malignant cells have changed such that they lose normal control mechanisms governing growth. These cells may invade surrounding local tissue or they may spread throughout the body and invade other organ systems.

Symptoms

The list of signs and symptoms mentioned in various sources for rectal cancer includes the symptoms listed below:

  • bright red blood present with stool
  • abdominal distention (stretching from internal pressure), bloating, inability to have a bowel movement
  • narrowing of the stool, so-called ribbon stools
  • pelvic pain
  • unexplained weight loss  
  • persistent chronic fatigue
  • rarely, urinary infection or passage of air in urine in males (late symptom)
  • rarely, passage of feces through vagina in females (late symptom)

Causes

Causes of rectal cancer are probably environmental in sporadic cases (80%), and genetic in the heredity-predisposed (20%) cases. Since malignant cells have a changed genetic makeup, this means that in 80% of cases, the environment spontaneously induces change. Those born with a genetic predisposition are either destined to get the cancer, or it will take less environmental exposure to induce the cancer. Exposure to agents in the environment that may induce mutation is the process of carcinogenesis and is caused by agents known as carcinogens. Specific carcinogens have been difficult to identify; dietary factors, however, seem to be involved.

Prevention

There is not an absolute method for preventing colon or rectal cancer. An individual can lessen risk or identify the precursors of colon and rectal cancer. The patient with a familial history can enter screening and surveillance programs earlier than the general population. High-fiber diets and vitamins, avoiding obesity, and staying active lessen the risk. In fact, a 2003 report said that vigorous exercise (to the point of sweating or feeling out of breath) lowered risk of rectal cancer by nearly 40% compared to those who exercised less. Avoiding cigarettes and alcohol may be helpful. By controlling these environmental factors, an individual can lessen risk and to this degree prevent the disease

Diagnosis

Screening evaluation of the colon and rectum are accomplished together. Screening involves physical exam, simple laboratory tests, and the visualization of the lining of the rectum and colon. X rays (indirect visualization) and endoscopy (direct visualization) are used to visualize the organs' lining. The physical examination involves the performance of a digital rectal exam (DRE). At the time of this exam, the physician checks the stool on the examining glove with a chemical to see if any occult (invisible), blood is present. At home, after having a bowel movement, the patient is asked to swipe a sample of stool obtained with a small stick on a card. After three such specimens are on the card, the card is then easily chemically tested for occult blood. These exams are accomplished as an easy part of a routine yearly physical exam.

Prognosis

Survival is directly related to detection and the type of cancer involved, but overall is poor for symptomatic cancers, as they are typically quite advanced. Survival rates for early stage detection is about five times that of late stage cancers. People with a tumor that has not breached the muscularis mucosa (TNM stage Tis, N0, M0) have a five-year survival rate of 100%, while those with invasive cancer of T1 (within the submucosal layer) or T2 (within the muscular layer) have an average five-year survival rate of approximately 90%. Those with a more invasive tumor yet without node involvement (T3-4, N0, M0) have an average five-year survival rate of approximately 70%. Patients with positive regional lymph nodes (any T, N1-3, M0) have an average five-year survival rate of approximately 40%, while those with distant metastases (any T, any N, M1) have an average five-year survival rate of approximately 5%

Treatment

Once the diagnosis has been confirmed by biopsy and the endorectal ultrasound has been performed, the clinical stage of the cancer is assigned. The treating physicians use staging to plan the specific treatment protocol for the patient. In addition, the stage of the cancer at the time of presentation gives a statistical likelihood of the treatment outcome (prognosis).