The colon is a part of the digestive tract that connects the stomach
and small intestine to the anus. The terminal portion of this colon is
called the rectum, spanning approximately 12cm in length. About 20% of
all cancers that occur in the colon arise in this rectum.
Bleeding
is the most common symptom associated with rectal cancer, occurring in
up to 60% of patients. Other frequent symptoms include change in bowel
habit, and abdominal pain.
The diagnosis of rectal cancer usually
involves colonoscopy, an examination of the colon using an instrument
called colonoscope that enables an evaluation of the entire inner lining
of the colon including the rectum. Once the diagnosis of cancer is
made, the extent of the disease is often determined using a radiologic
examination called CT scan. It allows an initial assessment of the
extent of spread of cancer. In addition, an endoscopic ultrasound may be
helpful in assessing the local spread of cancer. At the same time,
routine blood tests including complete blood count (CBC), liver function
tests, and a tumor marker called CEA are usually obtained during the
initial evaluation.
There are 4 stages of rectal cancer. Rectal
cancer is defined as Stage 1, if the cancer tissue is confined to the
lining of the rectum. In Stage 2 cancer, the cancer tissue has invaded
the layers of rectal wall, and may have invaded nearby organs such as
bladder or uterus. In Stage 3 rectal cancer, the cancer tissue has
spread to nearby lymph nodes, tiny bean shaped glands of lymphatic
system. In Stage 4 cancer, the cancer has spread to other organs such as
liver or lung.
The staging of rectal cancer is important since
the prognosis of affected individual is highly dependent on the staging
of cancer. For example, patients diagnosed with Stage 1 rectal cancer
have overall 5-year survival rate of 74%. On the other hand, those
diagnosed with stage 4 cancer can only expect 6% survival rate at 5
year.
The treatment of rectal cancer often involves combination of
surgery, radiation therapy, and chemotherapy. Because of the complex
anatomy of anal sphincter, there are various surgical techniques that
may be utilized to preserve the anal sphincteric function. In addition,
radiation therapy and chemotherapy are often administered to shrink the
tumor, prior to performing the surgery.
For cancer that is
localized and has not spread, the excision surgery is the treatment of
choice. More advanced cancer usually requires chemo-radiation therapy,
followed by surgery. The type of surgery performed will be dependent on
the exact location, size, and extent of cancer with the intent of
preserving anal sphincteric, if at all possible. Recently,
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