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    What is SRS/SBRT/SABR?
    Banner - Cancer Institute Apollo Hospital - Bangalore

    What is SRS/SBRT/SABR?

    Radiation therapy is a treatment method that employs radiation to address diseases like cancer. Specialists in radiation therapy use this approach to treat diseases, reduce tumour growth, and alleviate symptoms such as pain. The most prevalent form of radiation therapy is external beam therapy, where radiation is administered through a machine without penetrating the skin, similar to X-rays.

    An external beam radiation technique known as stereotactic radiation is utilised to deliver high doses of radiation from an external source precisely targeting tumours. There are two primary types of stereotactic radiation:

    1. Stereotactic Radiosurgery (SRS)
    2. Stereotactic Body Radiation Therapy (SBRT) or Stereotactic Ablative Radiotherapy (SABR)

    Let’s understand these methods one by one.

    Stereotactic Radiosurgery (SRS)

    Stereotactic Radiosurgery (SRS) is a minimally invasive radiation therapy technique that eradicates tumours in various body parts, including the brain, spine, and lungs, by employing high-intensity radiation. A team of radiologists and neurosurgeons performs SRS specialised in cancer treatment. Being a non-surgical approach, it eliminates the need for incisions.

    Stereotactic radiologists employ three distinct technology types to administer radiation in their treatments.

    1. GammaKnife: A state-of-the-art radiotherapy method used for treating brain tumours and other complex diseases with surgical accuracy.
    2. Linear accelerator (LINAC): This technology employs X-rays to precisely target cancer tumours with radiation while minimising the impact of radiation on surrounding healthy tissue.
    3. Proton Therapy: A specialised cutting-edge form of radiotherapy that utilises high-energy proton beams to accurately target tumours, thereby reducing or eliminating the exposure of surrounding non-cancerous tissue. This innovative form of radiosurgery is only available in a few hospitals, with Apollo Hospital being the first to introduce it in India.

    Condition Treated

    Surgical radiosurgery is employed to treat diseases affecting the brain or spine, including:

    1. Brain tumour recurrence, a form of cancer occurring in the brain.
    2. Brain tumour or brain metastatic cancer.
    3. The growth of benign tumours originating from the membranes surrounding the brain, which is a common occurrence.
    4. Benign inner ear tumours.
    5. Benign pituitary cell tumours.

    Risk of Stereotactic Radiosurgery (SRS)

    Stereotactic radiosurgery doesn’t involve making any cuts, so it’s generally less risky than other types of surgery. Any side effects that accompany it are typically temporary. These could include:

    • Feeling tired and fatigued is normal for a few weeks after undergoing stereotactic radiosurgery.
    • Signs and symptoms of brain swelling, either at the treatment site or in its proximity, may encompass headaches, nausea, vomiting, and other related symptoms.
    • The doctor might prescribe corticosteroid (cortisone) medications to prevent or treat these symptoms.
    • Patients might experience redness, irritation, or scalp sensitivity in areas where a device was placed on the head during the procedure. Some patients might also undergo temporary hair loss.

    In rare cases, patients may experience long-term side effects (such as other brain or nervous system issues) several months after the treatment.


    SBRT, also known as SABR, is a type of radiation that targets tumours within the body. The two terms are interchangeable. SBRT is used to treat both primary cancers (such as those originating in the lungs or prostate) and secondary cancers (those that may have spread to other parts of the body, such as the bone, lung, or liver). Typically, one to five treatment sessions are administered. It is a highly targeted radiation therapy that delivers a concentrated dose of radiation to a tumour while limiting the radiation dose to the surrounding tissues. It has become the preferred treatment for many patients with small-volume tumours for whom surgery might not be the most suitable option.

    Unlike other types of external beam radiation, this technique uses a higher dose of radiation to target the cancer. That’s why the term ‘ablative’ is sometimes used to describe this type of therapy. The higher doses are administered to the patient through X-ray beams directed externally and using a limited number of treatments. This delivery method is highly precise, and there are various technologies that can be employed to deliver this technique, including:

    • Linac-based technology
    • CyberKnife technology
    • Tomotherapy technology
    • Gamma Knife technology

    Condition Treated

    Stereotactic Body Radiation Therapy is a form of radiation therapy employed to treat small tumours within the chest, abdomen, or pelvic area that cannot be removed surgically or treated with traditional radiation therapies. These include:

    1. Tumours that originated elsewhere in the body and metastasized to the lung.
    2. Small Lung Cancer.
    3. Liver metastases, which are cancers that start in the liver and spread to other parts of the body.

    Risk of SBRT or SABR

    Getting Stereotactic Body Radiotherapy can be risky. It can cause side effects and even complications. Most of the time, the side effects are short-term and don’t last long, but there are a few that might persist for a while:

    • For the first few days following SBRT, one may experience extreme fatigue.
    • The treatment of a tumour in the vicinity of the intestine or liver may result in nausea or vomiting for a brief period of time.
    • Swelling at or close to the treatment area can lead to some short-term side effects like increased pain.
    • Skin irritation, itching, or dryness may occur in the treated area.

    In rare cases, some patients experience side effects that can last for months or even years following treatment. Side effects may include:

    • Swelling in the bones that could lead to fractures.
    • Acute swelling in the arms and legs. This condition is sometimes called “lymphedema.”
    • Changes in your bowels or bladder.
    • Changes in the spinal cord.

    What are the similarities between SRS/SBRT/SABR?

    • They all utilise multiple narrow beams of radiation.
    • They involve the use of immobilisation devices or methods to restrict, monitor, and adapt to any movement that may occur during treatment.
    • All three provide high-dose radiation in a safe and precise manner over a limited number of sessions.
    • Furthermore, they focus with accuracy on small, clearly defined areas.

    What is the difference between these Therapies?

    • Depending on the type of stereotactic system being used, some systems may only be capable of treating head tumours, while others can treat tumours in various parts of the body.
    • Stereotactic treatment schedules vary; certain treatments may be completed in a single session, whereas others might require a series of treatments over several days.
    • Various systems employ different methods to ensure patients remain in the correct position. Some incorporate special holders to secure the patient, while others utilise the machine to monitor any patient movements.


    The use of SRS/SBRT/SABR is generally recommended for the treatment of very small tumours. Specialised scans are used by physicians to determine the exact location of the tumour target. Certain treatment machines are capable of adapting to patient movement, such as during respiration. These techniques enable the doctor to deliver a high dose of radiation to the tumour in a relatively short period of time. An individual can receive one to five sessions of these therapies over a period of one to five weeks.

    Radiation treatments like SRS, SBRT, and SABR provide a patient with the exact amount of radiation they need immediately, which is much faster than other treatments. It is also very accurate, so a patient does not need to be concerned that it will affect other areas of the body. One drawback of SRS/SBRT/SABR is that it is only appropriate for the treatment of small, clearly defined tumours visible on CT or MR scans. Therefore, this approach is not suitable in all circumstances.

    Additionally, the radiation dose that can be safely administered may be reduced if the cancer is situated in close proximity to a delicate normal structure, e.g. the spinal cord or intestine. Apollo Hospitals Karnataka provides pain management for cancer patients with a wide range of options to help patients live a more comfortable life. Book your appointment today.

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