What is Stereotactic Radiotherapy (SRT)?
Stereotaxy refers to a method for highly precise three-dimensional localization of targets with known coordinates using an external frame of reference. Tumor targets are pinpointed using advanced magnetic resonance (MRI) and computed tomography (CT) imaging techniques in conjunction with an external frame or fiducials.
The main advantages of SRT are:
- Highly-optimized and conformal radiation doses
- Extremely accurate radiation beam delivery
- Potential for larger doses of radiation in fewer treatments (3 to 8 fractions)
The key element of the SRT procedure is alignment of the stereotactic frame with the isocenter of the X-ray treatment machine. This is accomplished within 1.0 millimeter specifications and is known to tenths of a millimeter. This accuracy is the crucial element of the SRT technique that allows delivery of focused high doses of radiation to a lesion while avoiding critical nearby structures - thus reducing side effects.
Stereotactic Body Radiotherapy (SBRT) for Non-small-cell Lung Cancer
SBRT is a stereotactic technique used for radiotherapy of early stage NSCLC that allows for the reduction of tumor treatment volumes and an increase in radiation dose to the tumor. The larger radiation doses lead to shorter treatment regimens (hypo-fractionation) and an overall improvement in the rates of tumor control and patient survival. A combination of multiple highly conformal radiations beams, highly precise image-guided tumor localization techniques and larger radiation doses results in the delivery of a very effective biological dose to the tumor, while minimizing radiation dose to surrounding healthy tissues. Recent comparisons of SBRT with surgery indicate that survival and local tumor control compare favorably for patients with Stage I disease. These studies suggest that SBRT may be a viable option for all patients with Stage I NSCLC, and especially for those patients for whom surgery may not be feasible.
Excerpt from Original Article
Radiotherapy for Lung Cancer By Jason Shoales, Medical Physicist, Certified by The American Board of Radiology in Therapeutic Radiological Physics
Bibliography
1. Cancer Facts & Figures 2009. American cancer Society; [http://www.cancer.org/downloads/STT/500809web.pdf]
2. Ruckdeschel, J. C. Myths & Facts about lung cancer: What You Need to Know. Manhasset, NY: CMPMedica; 2007. P. 1-17.
3. Coia, L. R.; Moylan, D. J. Introduction to Clinical Radiation Oncology. 3rd ed. Madison, WI: Medical Physics Publishing; 1998. P. 217-241.
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