Radiation and Cancer Treatment
Radiation therapy for cancer treatment is the use of ionizing electromagnetic radiation to preferentially kill tumor cells while minimizing damage to normal tissues, for the purpose of cancer cure or palliation. Since the discovery of x-rays, radioactivity and radium at the end of the 19th century, the first medical use of radiation to treat skin cancer, and the demonstration that locally advanced laryngeal cancer could be cured with fractionated radiation therapy, the field of radiation oncology has rapidly evolved.
Radiation therapy can be divided into 2 main categories: high energy external radiation that is delivered to the tumor from an outside source (external beam therapy), and internal radiation that is placed into the patient in close proximity to the tumor (brachytherapy). The types of radiation that are used in clinical practice to treat cancer most commonly include x-rays, gamma rays, electrons and protons, which differ in the way they are produced and in the way they interact with matter.
Over time, the delivery of ionizing radiation has become more precise with higher-energy machines and more accurate radiation treatment planning and delivery. Advances in technology have increased the complexity of radiation therapy. Because radiation is often combined with surgery and chemotherapy, the optimal treatment of the cancer patient depends on the close coordination of these different treatment modalities. Foundational to any radiation treatment is the accurate identification of the full extent of tumor and areas of possible spread. In addition to physical exam and radiographic findings including both anatomic as well as functional and physiologic imaging, a number of other factors contribute to this determination including the tumor histology as well as history of prior treatments. After scanning the patient (usually with CT) to understand the tumor in relation to other organs, defining the regions to treat and the normal tissues to avoid, radiation treatment is planned often with sophisticated, iterative processes whereby the tumor target is sufficiently treated and the normal tissue is sufficiently spared. Patients are treated most commonly between 5-8 weeks with daily radiation treatments, although can be treated with higher radiation doses with as few as 1-5 radiation treatments.
