Radiotherapy: Past and Present

Author: Dr. Csilla Pesznyák

 
The biological effects of ionizing radiation are known for more than a hundred years. Wilhelm Konrad Röntgen discovered the X-rays in 1895. The radiation effect on tissues of living organisms was observed in the following year. József Jutaassy used the X-rays for dermatological treatments in summer 1986, and he wrote an article on treatment in Wiener Medizinische Wochenschrift. Wilhelm Alexander Freud published the first study about therapeutic use of X-rays in Vienna in 1897. Antoine Henri Becquerel discovered radioactivity in 1986, and two years later Marie and Pierre Curie discovered the polonium and in 1989 radium. So the radioactive isotope applications could start in medicine. Becquerel and the Curies received the Nobel Prize in 1903.

 

 
Pierre Curie observed that the malignant tumors are more rapidly destroyed by the radium radiation than healthy tissues. Implanting radioactive sources directly into tumor tissues was first used by Alexander Graham Bell. Two early pioneers of brachytherapy, Henri-Alexandre Danlos from the Curie Institute in France and Robert Abbe from St. Luke's Memorial Hospital in New York tested the idea of shrinking tumors by exposure to radioactive materials. A vial of radium salt was placed on the breast of a woman with cancer, and the tumor was observed to shrink. Since Margaret Cleaves performed intracavitary brachytherapy for cancer of the cervix in 1903, the radiation therapy of cervical cancer has traditionally been based on low dose rate (LDR) intracavitary brachytherapy. The first article about Cleaves’ work was published in Medical Record (3rd. October 1903.) In the beginning of the last century, cancer was treated by radium and X-rays in the kV range.
The rapid developments of radiation therapy started after the end of World War II. The first cobalt unit was built in 1951 in the Radiation Therapy Center in Ontario, Canada. The first patient was treated at the end of October of the same year. The first prototype of accelerator operating with klystron was made by Russell Varian, Sigurd Varian, David Webster, William Hansen and John Woodyard in 1946 and named the Mark I. Edward Ginzton and Dr. Henry Kaplan, two experts for Stanford University, collaborated to implement a standard operational procedure, which could be used safely in a clinical setting. By the year 1960, the research of these experts resulted in the first publically used rotational radiotherapy linac known as the Clinac 6. In the United States the first patient was treated with linac in Stanford Hospital near San Francisco. The first patient treatment in Europe with a microwave linac took place on August 19, 1953. This was installed at Hammersmith Hospital in London. This machine used a 2 MW magnetron and 3 m wave guide on a stationary platform, producing an 8 MV beam and 100 R/min flattened over a 25 cm diameter field. At the same time in Sweden, physicist Lars Leksell and radiobiologist Borje Larsson started the first radiosurgical experiments on animals. As early as 1951, Leksell found that a single dose of X-ray radiation could destroy almost any deep-brain structure, without the risk of bleeding or infection. He called this technique stereotactic radiosurgery and defined it as the delivery of a single, high dose of radiation to a small and critically located target in the brain. A development of this technique is the Gamma Knife (1968) using a set of cobalt-60 as the radiation source.
Computed tomography (CT) was discovered independently by a British engineer named Sir Godfrey Hounsfield and Dr. Alan Cormack in 1972. It has become a mainstay for diagnosing medical diseases. For their work, Hounsfield and Cormack were jointly awarded the Nobel Prize in 1979. This was soon followed by the development of magnetic resonance imaging and positron emission tomography. The first 2D treatment planning system was made in 1978, and, in the end of the nineteens, 3D treatment planning systems with conformal treatment techniques were commercially released. At the beginning, the conformal techniques applied projection blocks, later replaced with multi-leaf collimator. The nineties introduced several new techniques such as intensity modulated radiotherapy, image guided radiation therapy and breath-holding radiotherapy.
With Cormack and Hounsfield’s invention of the CT, three-dimensional planning became a possibility and created a shift from 2-D to 3-D radiation delivery. CT-based planning allows physicians to determine more accurately the dose distribution using axial tomographic images of the patient's anatomy.
The treatment planning systems can account for the inhomogeneity information without any conversion software when the CT images are exported in DICOM file format. This option was the base of 3D treatment planning systems. Parallel with radiation therapy, radiobiology also was very rapidly evolving. This new knowledge makes it possible to perform dose escalation. The treatment with higher doses is possible with better patient fixation and positioning and with high level of quality control and quality assurance. The treatment planning has to take into account the patient anatomy, role of radiobiology and radiation physics. The radiation source is appropriate if it has the following properties:
1. The penetrating ability is proportional to the depth of tumor in body.
2. The open field has to be homogeneous.
3. The penumbra of the beam is as thin as possible.
4. The beam can be directed to the appropriate area of the patient’s body.
Three different radiotherapy techniques are used:
1. External beam of radiation therapy (teletherapy) – with external radiation source.
2. Brachytherapy - internal radiotherapy - radiation source is placed inside or next to the area requiring treatment.
3. Systematic radioisotope therapy with different radioisotope sources.

Literature

 
1. Adams GD. (1978) Formation and early years of the AAPM, Med. Phys. 5(4): 290-6.
2. Webb S. (2001) The future of photon external-beam radiotherapy: the dream and the reality, Phys Med, 17(4): 207-15.
3. Van Dyk J. Advances in modern radiation therapy. In: Van Dyk J. editor. The modern technology of radiation oncology, vol. 1. Madison: Medical Physics Publishing, 2005: 13-5.

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