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CancerQuest > Introduction to Patient Information > An Introduction to Cancer Treatments > Introduction to Radiation Therapy > How Radiation Therapy Works

How Radiation Therapy Works

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Radiation therapy (or radiotherapy) is an important technique for shrinking tumors. High energy waves are targeted at the cancerous growth. The waves cause damage within the cells, disrupt cellular processes, prevent accurate cell division, and ultimately cause the cells to die.⁽¹⁾ The death of the cells causes the tumor to shrink. One drawback of radiotherapy is that radiation is not specific to cancerous cells and may damage healthy cells as well.

Reactions of Normal and Cancerous Tissue to Therapy:
The response of tumors and normal tissues to radiation depends on their growth patterns before therapy starts and during treatment.⁽²⁾ Radiation kills cells through interactions with DNA and other target molecules. Death is not instantaneous, but occurs when the cells try to divide but fail-a process termed abortive mitosis. For this reason, radiation damage is manifest more quickly in tissues containing cells that are dividing rapidly⁽³⁾

Normal tissue compensates for the cells lost during radiation treatment by accelerating the division of the remaining cells. In contrast, tumor cells actually divide more slowly after radiation treatment, and the tumor may decrease in size. The degree of tumor shrinkage depends on the balance between cell production and cell death. Carcinomas are an example of a type of cancer that often has high division rates. These types of cancer tend to respond well to radiation therapy. Depending on the dose of radiation used and the individual tumor, the tumor may start to grow again after cessation of therapy, often slower than before. To prevent regrowth of the tumor radiation is often coupled with surgery and/or chemotherapy.⁽⁴⁾

References for this page:

1. Cancer Facts: Radiotherapy. National Cancer Institute, 1992. (April 2002.) [http://cis.nci.nih.gov/fact/7_1.htm]
2. Wang, C., M.D., ed. Clinical Radiation Oncology: Indications, Techniques, and Results. 2nd Edition. Wiley-Liss, Inc., 2000. 1-5.
3. Elizabeth Cohen-Jonathan, Eric J Bernhard and W Gillies McKenna. "How does radiation kill cells?" Current Opinion in Chemical Biology. (1999) 3(1): 77-83. [http://www.sciencedirect.com/science/article/B6VRX-419K3PM-G/1/24047f65a8465973ac3e7ce4fcbfe009] [PUBMED]
4. Denekemp J. Cell Kinetics and Cancer Therapy. Charles C. Thomas Publisher: Illinois, 1982. 3-5, 67-69, 88-89.