Host: The Japan Radiation Research Society
In the history of more than 100 years using x-rays, radiotherapy has now established its firm place in cancer therapy. Recently, through development of 3-D conformal radiotherapy that permits high dose delivery to the tumor with sparing the surrounding normal tissues, improvement of treatment results and expansion of indications have been achieved. Within two months after the discovery of x-rays, their potential for treatment of disease was realized and tested, and 3.5 years thereafter the first patient was successfully cured of cancer by radiation alone. Since then, x-rays had been extensively used in cancer treatment but tumor control was not so good with severe skin complications due to low energy of x-rays available and lack of knowledge about “optimal” fractionation.
In the 1950's when the megavoltage radiotherapy became available using the modern linear accelerator and 60Co unit, the potential ability of radiotherapy was remarkably expanded. In an effort to improve dose distributions using these machines, various techniques to improve dose concentration had been developed, and in early 1960's Takahashi developed cam-controlled multileaf collimators for conformational therapy with moving beams. Despite all these efforts, however, these analogue systems were never particularly successful and it soon became apparent that computerization was essential.
The introduction of CT scans developed in 1972, coupled with implementation of technologically advanced accelerators and sophisticated planning systems, have led us into a new era of high-tec radiotherapy. Charged particle with protons and carbon ions has also became available in more than 20 facilities worldwide. Advanced knowledge of radiobiology has also provided the impact on improvement of radiotherapy. However, it is important to realize not all developments have been without problem. The indications of various modalities have not been entirely known and costs are still expensive in many modalities.
As such, the major efforts of radiotherapy have been focused on technical developments to permit “more intensive and less toxic” treatment. In order to achieve this aim within 21st century, further developments in the field of radiation biology may also be needed. This will be also discussed in my talk.
