colon cancer symptom : What happens during radiation therapy?

Radiation is a special kind of energy carried by waves or a stream of particles. When radiation is used at high doses—much higher than the amount used to obtain x-ray images—it can destroy abnormal cells that cause cancer. It does this by damaging the cell's DNA, which eventually causes the cell to die.

Because of the importance of treating the cancer but sparing healthy tissue, you will visit the medical center a few times before actual therapy for treatment planning and simulation. Correct patient positions for radiation exposure are determined for accurate, effective therapeutic results. Your skin may be marked with permanent ink. Custom-made lead shields may be constructed to protect your healthy organs from the radiation, or the radiation fields may be shaped for your situation with special blocks inside the radiation machine.

What are possible side effects of radiation therapy?
Complications of radiation therapy may include diarrhea or frequent bowel movements, fatigue, appetite loss, and redness of the skin where external x-rays enter the body. Generally, side effects stop gradually once treatment is discontinued, but often bowel function remains altered from what it was before the disease started.

What kind of treatment follow-up should I expect?
Colorectal cancer can recur, or reappear, in a patient previously treated for the disease. Because patients can sometimes be cured after their tumor recurs, follow-up care is critically important.

Physical examination. Patients will undergo frequent physical examinations from a few weeks to many years after treatment, especially if side effects from the treatment do not subside or new symptoms develop. Symptoms of pain, unexplained weight loss, or bleeding can occur with tumor recurrence.
Blood tests. Follow-up evaluation usually includes periodic blood tests. An abnormal result may indicate that the colorectal cancer has recurred.
Colonoscopy. Approximately one year after treatment for colorectal cancer, patients usually undergo a colonoscopy, or examination of the colon with a tiny camera at the end of a hollow, flexible tube to detect recurrence or development of new benign or malignant masses. If findings from this examination are normal, it should be repeated three years later, then every five years after that.
Imaging. Also during follow-up examinations, a patient may undergo computed tomography (CT) or magnetic resonance imaging (MRI). The images obtained by using these devices can help determine treatment response and detect disease spread. Occasionally, a specialized screening procedure, called positron emission tomography (PET), can also be used to detect disease spread, but this is normally used only when other symptoms are present.

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