What is Stereotactic Radiotherapy?

Stereotactic Radiotherapy is a treatment in which very high doses of radiation are directed to the target in the body by using many beams of varying intensities and with millimetric precision from different angles. The rays from different angles converge on the target, creating the highest dose here while ensuring that the amount received by the surrounding normal tissues is minimal. Thus, the risk of undesirable side effects associated with radiotherapy is reduced.

 

In Stereotactic Radiotherapy, advanced imaging techniques such as computed tomography, magnetic resonance imaging, and similar are used to precisely determine the target and plan the treatment. Doctors draw typical structures in and around the target volume on the images. Then, it makes personalized treatment planning by adjusting the intensities and positions of the beams in the computerized planning system. Although stereotactic radiotherapy varies depending on the type and location of the tumor, it is usually administered 1-5 times once a day. The most suitable candidates for this method typically case with small and well-circumscribed tumors unsuitable for surgery. Stereotactic Radiotherapy comes to mind in some types of cancer as the first treatment option.

 

In Which Cancers Is Stereotactic Radiotherapy Used?

 

  • Lung cancer,
  • Liver tumors or tumors that have metastasized to the liver,
  • Tumors located in the spinal cord,
  • Pancreatic tumors,
  • Prostate cancer,
  • Bone metastases
  • Brain metastases
  • Recurrent disease

 

Stereotactic Radiotherapy Planning

It performs computed tomography in the treatment position and with patient-specific motion restraints. A patient-specific thermoplastic mask should be used in head and neck treatments, during the computed tomography performed for planning purposes, and during the treatment. This mask aims to ensure that the treatment area is immobilized and the tumor area is irradiated with absolute accuracy. Small markers (fiducial markers) may be required for treating the tumor or its close neighborhood. This procedure is performed with computerized tomography, and the doctor places a needle in the desired area. If he sees that this needle is in the appropriate place in the tomography, he places small gold markers in the same session. These markers can be seen on X-rays or tomography sections while the treatment is being applied, allowing the treatment to be applied to the target with millimeter accuracy.

The relevant physician determines the target volume by combining the planning tomography sections and the area’s MR or PET-CT image sections with being treated on the planning computer. Then he makes computerized treatment planning with the physical engineer. In this process, the aim is to protect the surrounding normal tissue while allowing the radiation beams to completely wrap the shape of the target with fewer safety limits. Thus, the possibility of treatment-related side effects decreases.

 

Stereotactic Radiotherapy Application

Stereotactic Radiotherapy can be applied with different devices;

  • LINAK,
  • Tomotherapy Device,
  • Cyberknife,
  • Proton Therapy Devices.

The Cyberknife device has a robotic arm that moves with the treatment table and has a tiny LINAK on its end. With the contribution of the table and mechanical arm movements, it is possible to send beams to the target from many angles. X-ray images taken regularly during the treatment are combined with images from the computer system to ensure precise irradiation of the target. Thus, the target is irradiated clearly even in the presence of respiratory-related tumor movement. Depending on the type of cancer and the tumor’s location, the treatment may take 30 minutes to 4 hours. The tomography images obtained during the tomotherapy device treatment are compared with those used in the treatment planning, and the target is confirmed. The treatment time can last 30 minutes-1 hour.

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