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HISTORY OF RADIATION THERAPY |
1890-1920
Radiation therapy had its beginning as a treatment of cancer soon after the discovery of x-rays by Roentgen, radioactivity by Becquerel and radium by Marie and Pierre Curie, which occurred shortly before the turn of the century. The first reported cure of cancer, a basil cell epithelioma, by this treatment modality appeared in the literature in 1899. During this time it was viewed as the "Dark Ages" of the evolution of radiation therapy as a treatment modality for cancer with, radium used as the source of radiation delivery.
Surgeons or dermatologists administered the radiation therapy treatment, with little understanding or knowledge of the physical nature and biological effects of radiation. There was no method of calculating the radiation dosage. The equipment used to deliver the radiation was primitive, temperamental and limited in energy so that only the cancers that were superficial cancers could be treated.
The radiation therapy of this era involved a massive exposure of radiation to a large area of the body with the hope that the tumor would be destroyed with a single treatment. Needless to say, many complications occurred after treatment with radiation due to the destruction of the normal tissues. The literature of this decade has many examples of tissue necrosis, infection, and death as a result of treatment. The rate of tumor recurrence was also reported as high.
"MANY OF THE FEARS AND MISCONCEPTIONS PRESENTLY RELATED TO RADIATION BEGAN DURING THIS EARLY PERIOD OF DEVELOPMENT."
1920-1940
The late 1920's saw the identification of a dosage unit, the roentgen, and the use of fractionated daily doses of radiation rather than a single massive dose. During this era, treatment schedules were defined and implemented, and the relationship between the radiation dosage and the biological effects was studied. Radiation therapy continued to be seen as a palliative method of cancer treatment with little or no curative effect.
This was the era of kilovoltage radiotherapy. With the introduction of the vacuum x-ray tube, capable of energies as high as 200 kV, cures of superficial cancers were soon reported. It became clear that machines capable of producing higher energies had to be developed in order to effectively treat cancer located below the surface of the skin.
1940-1960
Soon after WWII, radioactive cobalt, and a man-made substitute for radium was developed. This was the time period designated as the mega-voltage era, which witnessed the widespread use of radioactive cobalt along with the development of electrical devices of high energy such as the linear accelerator and the betatron. These machines produced x-rays capable of deep penetration, making it possible to treat tumors located below the skin surface. Severe skin reactions, which were an expected side effect of radiation therapy at this time, lessened in severity or became nonexistent since the maximum effect of radiation now occurred below the skin surface rather than on the skin surface.
Mega-voltage machines offered many advantages, such as greater penetration of the x-rays, a lower skin dose, less scatter to adjacent tissues and a greater accuracy of the treatment plan. Development of the treatment-planning computer brought fourth complex mathematical calculations necessary to determine the dose distribution within the treatment area. The computer calculations were completed with accuracy and speed. Roentgen, the measurement of the dose of radiation in the air, was replaced by the rad, which is the measurement of the dose of radiation absorbed by the tissues. Controlled clinical trials, to determine the biological effect of radiation therapy treatment plans, were also begun during this time period.
1960-Present Time
During this period of time, past development of the mega-voltage radiation machines, radiobiology, the computer and controlled clinical trials, were further developed and refined. Machines capable of delivering adequate doses of radiation to tumors located in all areas of the body are now available. These machines, also known as accelerators, are dependable and feature many refinements over the original machine.
Radiation therapy is no longer being viewed as the palliative means of therapy. Cure and control of cancers are now realistic goals of radiation therapy. Cure indicates the patient has a normal life expectancy for his/her age. If cure is not possible, radiation therapy can control cancer for a long period of time, during which the patient experiences a higher quality of life. If the disease is widespread or the tumor volume is so great that effective control of the malignancy is not possible, then the curative goal of radiation therapy becomes one of palliation. The benefits of palliative treatment are to reduce the size of the tumor in order to relieve pain, and relieve pressure on lymphatic, vascular or nerve pathways, to relieve obstructions, and to improve the patient's feeling of well being.
At the present time, radiation therapy is considered to be a major treatment modality for cancer.
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