What is Radiation Therapy?

Another topic that comes up quite often in the realm of cancer care is radiation. A little over half, or almost 60% of all cancer patients will receive radiation therapy as part of their initial course of treatment.

A lot of people here the word radiation and cringe. Most people think of radiation in terms of the A-Bomb, Hiroshima and Nagasaki. We have always been taught to limit our exposure to radiation because it can be harmful to us. I am here to explain to you what exactly Radiation Therapy is and why it is so helpful in the fight of cancer.

Radiation therapy (or radiotherapy) is the medical use of ionizing radiation as part of cancer treatment to control malignant cells (not to be confused with radiology, the use of radiation in medical imaging and diagnosis). Radiation therapy may be used for curative or adjuvant cancer treatment. It is used as palliative treatment (where cure is not possible and the aim is for local disease control or symptomatic relief) or as therapeutic treatment (where the therapy has survival benefit but is not curative).

Radiation therapy is commonly used for the treatment of malignant tumors (cancer), and may be used as the primary therapy. It is also common to combine radiotherapy with surgery, chemotherapy, hormone therapy or some mixture of the three. Most common cancer types can be treated with radiotherapy in some way. The precise treatment intent (curative, adjuvant, neoadjuvant, therapeutic, or palliative) will depend on the tumour type, location, and stage, as well as the general health of the patient.

Radiation therapy is a localized treatment. Unlike chemotherapy, which is administered in the blood stream and distributed to the entire body, radiation therapy is precisely delviered to a particular area of the body. With current advances in technology and computers, we can be as precise as one-half of one millimeter in delivering our radiation to a patient.

Benefits of radiation therapy include the preservation of normal function and better cosmetic results. As an example, cancer of the larynx is very curable. It can be treated with surgery or radiation therapy. Surgery may require the removal of the vocal chords, leaving a patient without a voice. Radiation however, may casue some discomfort in a temporary scratchy voice or sore throat, but that will go away after a few short weeks and a patient will still have there voice. One more example would be in prostate cancer, with surgery a patient may have impotence or severe problems with erectile function. With radiation therapy the nerves are spared, and there is little to no effect on erectile function.

There are two main branches of Radiation Therapy: External Beam Radiation Therapy (or distance therapy) and  Brachytherapy (or short distance). External beam is administered through a machine in which a high energy radiation beam is produced through an electrical current. When the machine is one, the radiation is present, and when it is off, there is no radiation. Brachytherapy on the other hand is a radioactive material that is always emitting radiation.

The goal of radiation therapy is to eradicate the cancer cells while not destroying the normal tissues in the treatment field. This is a bit easier said then done. Radiation interactions with matter are nonspecific. It is a random process that does not distinguish between malignant and normal tissues. This being said, this is how radiation works at a cellular level to rid patients of cancer.

Radiation therapy works by damaging the DNA (or “rules”) of cells. The damage is caused by a radiation beam directly or indirectly ionizing (or exciting) the atoms which make up the DNA. Indirect ionization happens as a result of the excitation of water, forming free radicals (or “breaks” in the rules), which then damage the DNA. In the most common forms of radiation therapy, most of the radiation effect is through free radicals. Because cells have mechanisms for repairing DNA damage, breaking the DNA on both strands proves to be the most significant technique in modifying cell characteristics. Because cancer cells have their rules for repopulation turned off, they reproduce more, and have a reduced ability to repair sub-lethal damage compared to most healthy normal cells. The DNA damage is inherited through cell division, accumulating damage to the other cancer cells, causing them to die or reproduce more slowly. Since normal tissues have mechanisms to fix these sub-lethal breaks, they fix themselves with in six hours, divide, and repopulate. This is what allows us to kill cancer cells, provide cures with radiation, and decrease the amount of side effects.

I will save the description of the different forms of radiation and treatment devices for Radiation Therapy for another blog.

If you have any questions regarding this blog, or want to know more about radiation therapy, chemotherapy, or anything else, please leave me a comment or email me directly at: cancergeek@gmail.com



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