What is Radiosurgery/ Stereotactic Radiosurgery?
A Neurosurgeon conceived Radiosurgery/Stereotactic Radiosurgery (SRS) in 1950 in the treatment of brain tumours. It uses a highly-concentrated dose of radiation to destroy tumour
cells and other problems in the brain, lungs, neck, spine, liver, and other parts of the body. SRS works by deforming and destroying the DNA of tumour cells, similar to other forms of radiation. Hence, these cells lose their ability to reconstruct and die. Stereotactic Radiosurgery of the spine and brain can be done in a single session. However, to treat lung, adrenal, liver, and other soft tissue tumours, body radiosurgery is required, which takes multiple sessions (typically three to five).
How is it different from radiotherapy?
Both Radiosurgery and radiotherapy use the same type of radiation. However, they are used in different situations and sometimes they complement each other. In cancer, in addition to the mass seen in the imaging (PETCT/MRI) there could be invisible cells spreading from the mass to the surrounding areas for some distance. Radiotherapy, given in small doses every day is used to treat both these groups of cells. Radiosurgery in focused and targeted fashion is used to handle only the mass seen in imaging and immediate adjacent area. In non-cancer conditions, since the cells do not go to surrounding tissue, radiosurgery is preferred. Stereotactic Radiosurgery can also exclude the surrounding healthy organs or tissues better than radiotherapy. Other benefits of Radiosurgery include:
- It uses a unique technique of focusing the radiation in 4D space and time
- When used in brain it is named Stereotactic Radiosurgery (SRS) and as Stereotactic body radiotherapy (SBRT) when used elsewhere. Recently the use of terminology Stereotactic Ablative Body Radiotherapy (SABR) is preferred in the latter situations.
- It takes one to five session to complete, whereas radiotherapy takes one to eight weeks
- It acts as a biological knife which “cuts off” cancer cells, and dead cancer cells are placed to breakdown
At Aster CMI, the Radiation Oncology TEAM use Varian True Beam STx with 6DoF Robotic Positioning system. It is an advanced, top of the linear accelerator machine designed to treat tumours in many parts of the body. It is a noninvasive machine that combines a robotic couch (which is capable of 6D motion) and various advanced imaging guidance systems to map the specific area of the patient and the tumour during treatment.
When Radiosurgery is useful?
- Instead of surgery: Radiosurgery can’t be used in all situations. It’s done when surgery is the treatment of choice, but can’t be implemented due to high risk for surgery, because radiosurgery can be done safely even in elderly patients
- With surgery: Radiosurgery is also supplemented after surgery when some part of the tumour is left behind or to reduce tumour size making it easier to remove with surgery
- With radiotherapy: It can also be used after IMRT/IGRT when portion of tumour is still present. Sometimes, it makes sense to use radiotherapy for visible and invisible cell extensions and finally deliver within 2-3 sittings of radiosurgery to the visible portion of cancer (radiosurgery boost)
- Alone: If the cancer is in the earlier stage, radiosurgery alone can be used as a treatment option
- Non-cancerous conditions: It’s also used in non-cancer conditions, especially in brain lesions when surgery is not possible or to help the surgery.
What are the recent developments in Radiosurgery?
In all the below given situations timing and a proper combination is essential.
- Radiosurgery is used nowadays even in early stage 4 cancers
- Radiosurgery can be used as a treatment option when one or few number of metastases (oligo-metastases) are present in any part of the body
- It’s also be used when one or few metastases remain after completion of chemotherapy cycles
- Cancer may be present in several parts of the body when chemotherapy/immunotherapy is started. After chemotherapy many times when the response is effective, smaller size tumours might disappear. In this situation, when the tumour remains only in a few locations, radiosurgery is useful.
- Recently, a combination of chemo-immunotherapy or immunotherapy with radiosurgery is found to cause an abscopal effect. That means, when radiosurgery is done in some part of the body with immunotherapy, visible tumours or invisible tumours elsewhere in the body might regress or disappear.
- It can be combined with treatments, such as RFA or Microwave ablation for improved control.
What are the Conditions Treated?
Around 50 years ago, Stereotactic Radiosurgery was discovered as a noninvasive and safer treatment option to treat tumours without an incision in the skull, skin, and membranes surrounding the brain and brain tissue.
The Radiosurgery as a new technique becomes popular to treat a variety of neurological and other conditions, such as:
Brain tumour: Benign and malignant brain tumours may be treated using Stereotactic Radiosurgery. It also helps in treating the cancers that have spread from other parts of the body to the brain (brain metastases).
Trigeminal neuralgia: Trigeminal neuralgia causes chronic pain, which transfers sensory information between the brain and areas of your cheek, forehead, and lowers jack.
Stereotactic Radiosurgery helps in reducing these pain signals.
Arteriovenous malformation (AVM): An AVM occurs when there is an abnormal tangle of blood vessels. It may disrupt normal blood flow and cause stroke or bleeding.
Stereotactic Radiosurgery blocks the AVM and helps the affected blood vessels to close off over time.
Acoustic neuroma: An acoustic neuroma, also known as vestibular schwannoma is a noncancerous cell that grows on the vestibular and hearing, leading from the inner ear to the brain. It can lead to loss of balance, hearing loss, ringing in the ear, and dizziness. As it grows, it affects the muscle movement of the face and sensations.
Stereotactic Radiosurgery may help in reducing the size of an acoustic neuroma and risk of permanent damage of nerve.
Pituitary tumours: Pituitary gland are responsible for controlling hormones in the body that control other functions such as growth, stress response, sexual function, and metabolism. Pituitary gland tumours are not cancer but can lead to severe problems.
Radiosurgery may help in shrinking the tumour and reduce the disruption of pituitary hormone regulation.
Other cancers: It may also be used to treat tumours of the lung, liver, kidney, spine and recurrent cancers.