Read more about CyberKnife® in an article by Consultant in Clinical Oncology, Dr Andrew Gaya. Cancer is the second leading cause of death in the United States and presents a worldwide health pandemic. Approximately 50% of all men and 33% of all women in the United States will develop cancer during their lifetimes. There was an estimated 564,000 cancer related deaths in the US with an additional 1.4 million newly diagnosed cancer cases in 2006. The leading cause of death in both male and female patients was lung and bronchial cancers, while prostate and breast represented the largest contingent of newly diagnosed cancers in males and females, respectively. Although cancer incidence rates for both sexes combined have remained stable from 1992 through 2003, overall cancer related deaths in the U.S. continue to decline. In fact, over 10 million people in the U.S., approximately 3.4% of the population, are cancer survivors. Technological advances in cancer detection and cancer treatments have played a key role in this growing trend.
There exist four conventional methods of treatment for cancer:
- surgical intervention
- chemotherapy
- immunotherapy
- radiation therapy
Radiation therapy becoming treatment of choice – why and how?
The development of Image-guidance in the delivery of radiation therapy (IGRT) has provided the capability of real-time imaging and real-time adjustment of the therapeutic beams to compensate for target motion. From this evolution in therapeutic radiation delivery and imaging techniques has emerged a technology which allows highly conformed and precisely delivered radiation treatment, recognised as stereotactic radiosurgery. SRS is a technique in which a single ablative dose (or 2-5 fractionated doses) of highly collimated radiation is delivered to one or more targets with submillimeter precision. SRS differs from conventional radiotherapy in that the efficacy of radiotherapy depends primarily on the greater sensitivity of tumour cells to radiation relative to normal tissue. Therefore, with all forms of radiotherapy, the spatial accuracy with which the treatment is focused on the tumour is a secondary concern because the normal tissues are protected by administering the radiation in fractionated doses. In contrast, radiosurgery requires much greater targeting accuracy since with SRS; normal tissues are protected by selectively targeting only the abnormal lesion, and using cross-firing techniques to minimize the exposure of the adjacent anatomy. Since highly destructive doses of radiation are used, any normal structures and tissue within the targeted volume are subject to damage as well. Although the radiobiology of radiosurgery is still evolving, it is held that the high radiation dose delivered to the target volume by radiosurgery may result in tumour control through direct early effects of apoptosis and mitotic death, late vascular changes, and stimulation of immune response.
