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Three Different Types Of Stereotactic Radiotherapy Explained

Stereotactic radiosurgery (SRS) is one of the best treatments for cancer, as it focuses radiation directly into the tumours to kill the invasive cancerous cells. 

To find out more about the different types of SRS and how they work, read on. 

What is SRS?

Instead of removing a tumour through surgery, SRS works by projecting radiation into the targeted area.

It is normally used to treat rumours that are hard to access through surgery, such as the brain. When targeting other areas of the body, it can sometimes be known as stereotactic body radiotherapy (SBRT) or stereotactic ablative radiotherapy (SABR). 

This treatment damages the affected cells by targeting the beams into one area, making them unable to grow by closing off blood cells and, ultimately, causing them to break down. 

SRS, which uses 3D imaging to target the radiation beams, does not impact the surrounding tissue, which means healthy cells can remain intact as much as possible. 

Thanks to its ability to avoid damaging the area surrounding the tumour, it comes with reduced side effects compared with other types of cancer treatment, which is why it is becoming an increasingly popular choice. 

Some of the complications that are associated with SRS, however, are fatigue for the first few weeks; headaches, vomiting and nausea due to swelling in the brain if that is the area being treated; and irritation at the site. 

What are the three main types of SRS?

SRS varies depending on the type of treatment, whether it is gamma knife, proton beam therapy, or linear accelerator SRS.

Gamma knife 

Gamma knife radiosurgery is perhaps the most famous of all three, as it is an effective way of targeting brain tumours. 

It works by targeting around 200 beams of grammar rays into small or medium-sized tumours. This type of procedure can also be used to treat brain lesions. 

In most cases, a head frame is used, which fastens to the skull and prevents the patient from moving their head during the treatment, making sure the beams are targeted to the right area. 

They also typically have to wear a mask with hundreds of holes in over the head frame, which further helps direct the radiation beams. 

The length of the procedure varies depending on the problem and its location, with simple treatments taking just a few minutes while more complicated ones can take several hours. 

Proton beam radiotherapy 

Another form of stereotactic radiosurgery is proton beam therapy, which uses high energy protons to target the tumour. 

The procedure, which is painless for patients, works by reducing the size of the tumour through a dose of protons that provide a burst of energy when they stop. Therefore, if they are targeted at a tumour, this is where they explode and end up destroying the cancer. 

It is typically used in highly complicated brain, head and neck cancers where it is essential the surrounding healthy tissue is not impacted to prevent serious complications to the patient. 

Treatment tends to last around an hour and needs to be repeated daily over five days for six weeks. 

As with other types of radiosurgery, the side effects tend to be restricted to the site of the treatment. For instance, your skin might become sore or you may lose some hair. Additionally, patients often feel tired for a few weeks after. 

Linear accelerator (LINAC)

Linear accelerator radiosurgery is often known as LINAC, and treats cancers by targeting X-rays or photons to affected areas. 

Instead of radioactive material like Gamma Knife radiosurgery or protons like proton beam therapy, it works by using X-rays instead. 

LINAC is typically used to treat patients who have larger tumours or whose affected area is too big to target with Gamma Knife. 

It can, therefore, be used to treat areas of the body other than the brain, including breast, oesophagus, rectum, stomach, uterus, prostate, bladder, liver, bones, head and neck. It works by the machine moving around the site to target the tumour from different angles.

A course of treatments typically lasts between one and five sessions. The side effects from LINAC are usually temporary and tend to include skin changes, such as itching or irritation, as well as fatigue. 

There might also be other symptoms, including digestion issues or difficulty swallowing, depending on what area is being treated.  

The type of SRS your oncologist at the radiotherapy centre will suggest will depend on the location of the tumour, its size, its grade and severity.