Doctors use radiation to target cancer cells with the goal of stopping tumor growth and destroying the cancer cells. The radiation works by damaging the DNA of the cancerous cells, which causes those cells to shrink and die.
Radiation can also affect nearby healthy cells, but they usually recover at a faster rate than the cancer cells. However, doctors try to prevent potential side effects that can happen when healthy tissue and organs are exposed to the radiation by protecting them with different methods. The methods can include low dose radiation, treatment sessions that are spread out over time and newer techniques that allow for more precision-focused treatment.
Your medical team will assess your specific spinal tumor and its sensitivity to radiation based on several different factors, which may include the type of cancer, size and number of tumors and placement of tumor(s). Depending upon the type of radiation therapy your doctor prescribes, the way that the cancer-fighting treatment is delivered will differ.
Go to What is Radiation Therapy for more information on external beam radiation therapy including stereotactic radiosurgery and fractionated stereotactic radiotherapy.
You will work with your cancer team to discuss all the options and decide upon the best course of treatment based on your cancer.
Radiation may be used to treat spinal cancers in different ways:
There are unique challenges when delivering radiation to the spine. Spine tumors grow close to the spinal cord, which cannot safely take high doses of radiation. The curvature of the spine, and the unique shape of vertebrae add to the challenges of delivering a tumorocidal dose. Unlike the skull, the spine cannot be fixated in place with a stereotactic mask or frame so there is also movement that must be taken into consideration when delivering radiation.
Real time image guidance combined with patient position monitoring during treatment allow for targeting accuracy to 1mm or less. Image guided radiation therapy (IGRT) and volumetric modulated arc therapy (VMAT) are sophisticated visualization, planning and delivery tools designed to facilitate high doses of radiation to the tumor while sparing the spinal cord and nerves. These technologies help clinicians deliver safe and effective treatment, even to radiation-resistant tumors.1
Patient Position Monitoring Technology
Patient position monitoring helps to maintain the accuracy of the procedure and ensure that the treatment dose is being delivered as prescribed by the cancer treatment team. Different delivery techniques offer different types of patient positioning and monitoring technologies.
Spinal radiosurgery patients often suffer from severe pain which can make immobilization challenging. Deviations or unintended shifts from the prescribed treatment position are automatically detected by the motion control technology during treatment delivery and immediately displayed to the user so action can be taken.
Hardware
Radiation is typically delivered using a machine called a linear accelerator.
When a linear accelerator is used, the treatment X-ray, or beam, comes from the machine’s head, called the gantry, and can be circular or shaped to the tumor. While the patient lies on a specially designed treatment table, the linear accelerator rotates around the patient’s mid section, delivering the radiation beams to the tumor from different directions and angles. By doing this, the tumor receives the most radiation while the healthy tissue around the tumor receives less radiation.
Advancements in LINAC hardware include mechanics that allow doctors to shape the radiation very precisely2,3 to the tumor. This helps reduce the radiation to healthy tissue and the spinal cord while at the same time allows a higher dose of cancer-fighting treatment to be delivered to the tumor.
There are many different treatment systems on the market. It is best to discuss your specific condition with your cancer care team to determine which type of treatment may work best.
Treatment Planning Software
The newest and most advanced software tools utilize techniques amassed from leading medical experts in the field of stereotactic radiosurgery. The tools offer automation and consistency, accuracy and targeting, all of which helps doctors customize the treatment plan to each patient and his or her tumor.
Using sophisticated software, doctors are able to effectively plan, verify and validate radiation therapy before delivering it. The tools allow for the accurate4,5 delivery of the treatment dose to the tumor while at the same time protecting organs like the spinal cord and other critical structures like the cauda equina. The cauda equina is a bundle of spinal nerves and spinal nerve rootlets.
Planning tools facilitate effective treatment mapping with precise tumor outlines and proper dose gradients so clinicians can analyze how the radiation decreases from a high point at the tumor’s center to lower at the tumor’s edge to almost nothing for nearby surrounding healthy tissue and the spinal cord.
Image Guided Radiotherapy
There are many different techniques used to deliver radiation to tumors. In the positioning of the patient prior to and during treatment, images are used for accuracy and to detect any movement. When the images are generated in the radiation treatment room, the process is called image guided radiotherapy (IGRT).
Volumetric Modulated Arc Therapy
Volumetric modulated arc therapy (VMAT) offers an advanced technique that allows clinicians to achieve highly conformal radiation dose distributions. At the same time, VMAT helps improve radiation coverage to the tumor while sparing healthy surrounding tissues and the spinal cord when compared with conventional radiotherapy techniques. VMAT also has the potential to offer additional advantages, such as reduced treatment delivery time compared with conventional static field intensity modulated radiotherapy (IMRT).6
1 Fridley, J.S., Hepel, J.T., MD; Oyelese, A.A. Current Treatment of Metastatic Spine Tumors – Surgery and Stereotactic Radiosurgery. Recent Advances in Neurosurgery.
2 van Santvoort, Jan et al. Positioning Accuracy in Stereotactic Radiotherapy Using a Mask System With Added Vacuum Mouth Piece and Stereoscopic X-Ray Positioning Int J Radiat Oncol Biol Phys, Volume 72, Issue 1, 261 – 267.
3 Lamba, Michael et al. Evaluation of Image-Guided Positioning for Frameless Intracranial Radiosurgery. Int J Radiat Oncol Biol Phys, Volume 74, Issue 3, 913 – 919.
4 Ramakrishna, Naren et al. A clinical comparison of patient setup and intra-fraction motion using frame-based radiosurgery versus a frameless image-guided radiosurgery system for intracranial lesions. Radiother Oncol, Volume 95, Issue 1, 109 – 115.
5 Feygelman, Vladimir et al. Simulation of intrafraction motion and overall geometric accuracy of a frameless intracranial radiosurgery process. J Appl Clin Med Phys, Volume 9, Number 4, Fall 2008.
6 Teoh, M. et al. Volumetric modulated arc therapy: a review of current literature and clinical use in practice. Br J Radiol. 2011 Nov; 84(1007): 967–996.
