Stereotactic Radiation Therapy (SRT)

Stereotactic radiation therapy (SRT) is used to treat small brain tumours that are either malignant or benign. It is used to treat tumours deep within the brain or tumours that cannot be removed surgically because doing so would damage too much normal brain tissue. SRT may also be used to treat tumours within the neck or spine.

Using high doses and precision targeting SRT treatment takes only a few sessions meaning treatment can be finished in days instead of weeks. With SRT, small beams are targeted at the tumour from many different angles. Because the beams meet at the tumour it gets a full dose of radiation, but the surrounding healthy tissue gets a much smaller amount. This technology was made possible, in part, by a donation from the Angela d'Audney foundation

In more detail

Stereo means 3-dimensional (3-D) and tactic means to probe. Stereotactic radiation therapy allows radiation beams to be given to a very specific area, usually the brain or spine. It is a non-invasive technique that delivers a high dose of radiation using many small sized beams, each carrying small doses from different angles. The treatment planning for SRT is highly complex, allowing each beam to be aimed very precisely. The result is that the tumour receives a high dose while minimising radiation exposure to surrounding healthy tissues. 

SRT is used to treat small, well-defined tumours in the brain or deep within the body. ARO uses a linear accelerator to deliver a large dose of radiation in a single or a few stereotactic treatments. When treating brain tumours, the head must be kept in the same position for each treatment. Patients receiving SRT to the head or neck will wear a removable head frame or mask during their planning scans and treatment to ensure accuracy of radiation delivery. 

Radiation therapy  is evolving rapidly, with ground breaking techniques like stereotactic and hypo-fractioned therapies increasingly becoming standard care for many cancers like tumours in the lung, liver and pancreas or secondary brain tumours. This innovative treatment is less invasive than surgery, may be more applicable to a broader range of cancers and reduces treatment time to days instead of weeks.  

Higher doses of radiation, 4D image guidance, and a robotic patient positioning HexaPOD™evo couch system are features of the stereotactic radiation therapy treatment. The couch system provides six degrees of freedom positioning including translational and rotational corrections. These technologies allow the patient to be positioned to within less than a millimetre, and greatly enhance accuracy when targeting the tumour.


Stereotactic body radiation therapy (SBRT)

Stereotactic body radiation therapy (SBRT), also called stereotactic ablative radiotherapy (SABR), is a type of radiation therapy in which a few very high doses of radiation are delivered to small, well-defined tumours. It is a precise kind of radiation therapy - accurate to within one to two millimetres.

SBRT is typically used to treat small, early-stage tumours of the lung, or isolated recurrences from various types of cancer. These are generally tumours that can’t be surgically removed because they move within the body, are too hard to reach surgically or too close to vital organs.   Because SABR is so precise, less of the surrounding healthy tissue is affected and radiation can be delivered at a much higher dose. This means that treatment can be completed in shorter time frames than traditional radiation therapy. To learn more please read Dr Louis Lao about SABR and it's uses and benefits (article on page 11 of this publication).

In more detail

SABR is typically used to treat small, early-stage tumours of the lung, or metastases from various types of cancer. SABR has also been used successfully to treat early-stage non-small cell lung cancer, recurrent lung parenchyma cancer, pancreatic cancer, and metastatic cancers in the Lung, Liver and Adrenal glands. 

Further information is is available on this factsheet from Oncology Nurse Advisor about Metastatic Cancer

SABR uses the latest image guidance technologies to treat tumours with millimetre-scale accuracy. The ability to spare healthy tissue while intensifying the radiation dose is the primary advantage of SABR over other treatment modalities, particularly when critical structures are located near the treatment area.   This precision is enabled by a combination of advanced techniques and technologies. Three or four dimensional imaging like 4D-CT, MRI, and PET-CT determine the exact size, shape and location of the tumour. 

Similarly, image-guided radiation therapy (IGRT) confirms the location of a tumour just before or during the delivery of radiation. This, combined with immobilization systems such as HexaPOD™ evo RT System and BodyFIX®, to keep the patient still, means the radiation beams stay focussed the tumour.   Although SABR can be delivered in higher doses, treatment of larger tumours may still be spread over a number of sessions. This is usually referred to as fractionated stereotactic radiotherapy. In larger tumours more healthy tissue is being exposed to radiation, which can cause more severe side effects. Lowering the dose and fractioning the treatment gives the normal tissue time to heal. 

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