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Radiation Treatment for Colon Cancer
Radiation treatment for colon cancer, also known as radiotherapy for colon cancer, is a type of treatment for colon cancer using high energy particles or waves (eg: X-rays, gamma rays, electron beams) to destroy the cancer cells.
Radiotherapy breaks the DNA strands within the cancer cell that control the abnormal growth rate, multiplication of cancer cells. Unlike chemotherapy that exposes the entire body to drugs that kills cancer cells, radiotherapy is usually a regional treatment, focusing on the cancer affected part only. Thus, with such a targeted treatment, those surrounding healthy tissues are less affected.
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Possible Indications for Radiation Treatment
Clinical oncologists may consider radiation therapy for colon cancer patients for the following reasons:
• To destroy residual cancer cells that are found after surgery.
• To prepare the patient for surgery by shrinking the large tumor prior to surgery. This would facilitate the surgical removal of the tumor.
• To relieve the symptoms of colon cancer (pain, bleeding and obstruction) particularly important in palliative care.
• To prevent the cancer recurrence after surgery.
Interestingly, the radiation therapy can be given either as a combination (with chemotherapy or/and surgery) or alone. Certain drugs are capable of making the cancer cells more sensitive to radiation therapy, allowing the radiation to kill more cancer cells effectively. These kinds of drugs are known as radiosensitizers.
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Types of Radiation Therapy
Basically, there are mainly two distinct types of radiation therapy for colon cancer:
External Beam Radiation Therapy: Machine generates radiation outside the body targeting the tumor site. The beams of radiation can destroy the DNA of the cancer cells and thus kill them. Careful planning prior to therapy allows the surrounding healthy tissues to be spared.
Internal Radiation Therapy or Brachytherapy: Unlike the external beam radiation, the source of radiation is placed within the body near the cancer site. It is usually given as an extra dose or boost of radiation to the site of surgery.
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Possible Side Effects After Radiation Treatment
Once the treatment is discontinued, the side effects usually disappear gradually. However, the bowel function remains altered from what it was before the disease started. Possible side effects occurring after radiation treatment may include diarrhea, frequent bowel movements, fatigue, redness of skin, fatigue and loss of appetite. Many patients are rather surprised to know they are coping better with radiation compared to chemotherapy.
Patients and family members must be reassured that patients are not radioactive after external radiation therapy. This is a myth and must be dismissed so that patients will not be isolated or asked to avoid socializing with other. Though brachytherapy gives off radiation, the radioactivity is confined around the radiation source and not the patient’s entire body.
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Follow Up After Radiation Treatment
Follow up is an important aspect of the management for colon cancer. During the follow up, the clinical oncologists would carry out few investigations besides the physical examination.
• Physical Examination: To elicit some signs which may suggest tumor recurrence, especially if the side effects from the cancer treatment do not subside or new symptoms develop.
• Periodic Blood Tests: Tumor markers like CEA (Carcinoembryonic Antigen) can help the doctor to check if the patient is responding to the cancer treatment thus far. It is also useful after the completion of treatment, to check if the cancer has returned.
• Colonoscopy: It is a method using a small tiny camera at the end of a flexible tube to detect recurrence or new formation of any growth under direct visualization within the colon. Usually, patients undergo a colonoscopy one year after treatment. The subsequent colonoscopy depends on the findings of the first one and usually when it is normal, it is to be repeated every three years.
• Imaging Technology: These include the Computed Tomography (CT), Magnetic Resonance Imaging (MRI) and also Positron Emission Tomography (PET) which are able to detect the possible spread of the disease. The choice of imaging technology depends on the site of involvement as well as the presence of other symptoms.
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1) After Treatment-Patients are Not Radioactive by Kenneth C Lane, MD, Director, Radiation Oncology, Assistant Professor, MetroHealth Medical Center, Case Western Reserve University
2) Treatments for Colon Cancer: Follow-Up Care for Colorectal Cancer, reviewed by Arnold Wax, MD, Oncologist
3) What are the treatments and survival for colon cancer? Medical Author: Dennis Lee, MD