Stereotactic Body Radiation Therapy

Introduction

If your cancer team has discussed stereotactic body radiation therapy — usually shortened to SBRT — as part of your treatment plan, this guide is written for you. It explains what SBRT is, how it differs from other forms of radiation, which cancers it is used for, how planning and treatment unfold, and what to expect during and after the sessions.

SBRT is one of the more recent advances in radiation oncology. It delivers a high dose of radiation to a small, well-defined tumour in only a few sessions — often between one and five — using advanced imaging and motion control to protect the healthy tissue around the tumour. For some patients, especially those who cannot have surgery, SBRT has become an important option in the modern treatment toolbox.

This article walks through SBRT as a modality, not as a one-size-fits-all answer. Whether SBRT is suitable for any individual patient is a decision made by a radiation oncologist working with the wider cancer team, taking into account the type and stage of cancer, the tumour's location and size, and the patient's overall health.

What Is Stereotactic Body Radiation Therapy?

Stereotactic body radiation therapy is a form of external beam radiation. “External beam” means the radiation is delivered from a machine outside the body, aimed precisely at the tumour. “Stereotactic” means the tumour is located using a three-dimensional coordinate system, similar to how a GPS pinpoints a location on a map. “Body” distinguishes it from stereotactic radiosurgery (SRS), a related technique used mainly for tumours in the brain.

The defining features of SBRT are:

• High dose per session. Each treatment delivers a much larger dose of radiation than conventional radiotherapy.
• Few sessions. A full course is usually one to five sessions, completed within one to two weeks.
• Sub-millimetre accuracy. Advanced imaging and immobilisation allow the beams to be aimed with very high precision.
• Steep dose fall-off. The radiation dose drops sharply at the edge of the tumour, sparing nearby healthy tissue.

SBRT is described and supported in current guidelines from major radiation oncology societies, including the American Society for Radiation Oncology (ASTRO) and the European Society for Radiotherapy and Oncology (ESTRO), and is included in NCCN treatment guidelines for several cancer types.

How SBRT Differs from Other Radiation Techniques

Several radiation techniques may be discussed during your consultations. Understanding how they differ can make conversations with your radiation oncologist easier.

• Conventional external beam radiation therapy (EBRT) uses smaller daily doses spread over many weeks, often 20 to 35 sessions.
• Intensity-modulated radiation therapy (IMRT) shapes and varies the strength of the radiation beams to match the tumour. It is often delivered over many sessions.
• Image-guided radiation therapy (IGRT) uses imaging just before or during each session to confirm the tumour's position. IGRT is built into SBRT.
• Stereotactic radiosurgery (SRS) uses the same high-precision, high-dose approach as SBRT but is used for tumours in the brain and the spine close to the brainstem.
• Proton therapy uses protons instead of X-ray photons; it is a separate modality with its own indications.

SBRT can be thought of as applying the precision and high-dose, few-session approach of stereotactic radiosurgery to tumours in the rest of the body.

Key Radiation Terms

• Gray (Gy). The unit used to measure radiation dose absorbed by tissue.
• Fraction. A single radiation session. The total dose is divided into fractions.
• Fractionation. The schedule of how the dose is split. SBRT uses few, large fractions; conventional radiotherapy uses many, small ones.
• Target volume. The area defined by the radiation oncologist as the tumour plus a planned safety margin.
• Organs at risk. Nearby healthy structures (such as the spinal cord, oesophagus, or bowel) that need to be protected during planning.

How SBRT Works

Radiation damages the DNA inside cells. Cells whose DNA is badly damaged cannot divide normally and eventually die. Cancer cells are generally more vulnerable to this damage than healthy cells, and healthy cells are also better at repairing themselves between treatments. Conventional radiotherapy uses many small doses to take advantage of this difference. SBRT uses a different strategy: a few very high doses, delivered with such precision that the steep edge of the radiation field protects the surrounding healthy tissue.

To make this possible, SBRT relies on several technologies working together.

Advanced Imaging

CT, MRI, and sometimes PET scans are combined to produce a detailed three-dimensional map of the tumour and the structures around it. This map is the basis for the entire treatment plan.

Motion Management

• 4D CT scanning captures the tumour's movement across the breathing cycle.
• Breath-hold techniques ask you to hold your breath at a specific point in the cycle while the beam is on.
• Respiratory gating only delivers radiation during a specific phase of breathing.
• Real-time tracking follows the tumour or markers placed near it during treatment.

Precise Beam Delivery

Which Cancers Are Treated with SBRT?

SBRT is currently used in the management of:

• Early-stage non-small cell lung cancer, particularly when surgery is not advisable due to other health problems. Guidelines including NCCN describe SBRT as a standard option in this setting.
• Liver tumours, including primary liver cancer (hepatocellular carcinoma) and selected liver metastases.
• Prostate cancer, where SBRT delivered in five sessions is included in major guidelines as an option for selected patients.
• Pancreatic cancer, often in combination with chemotherapy.
• Spinal tumours, including selected spinal metastases.
• Kidney and adrenal tumours, particularly when surgery is not suitable.
• Oligometastatic disease — a situation where cancer has spread to a small number of sites (typically up to five). SBRT may be used to treat each metastasis with the aim of slowing the disease and, in some patients, extending the time before further treatment is needed.
• Reirradiation in selected situations, when a tumour returns in or near a previously irradiated area.

Whether SBRT is appropriate for any individual is a clinical decision made by the radiation oncologist together with the broader multidisciplinary cancer team, after reviewing imaging, biopsy results, and the patient's overall health.

When SBRT Is Considered

Situations in which SBRT is commonly considered include:

• Early-stage tumours in patients who cannot safely undergo surgery because of age, lung function, heart disease, or other conditions.
• Patients who decline surgery and want a non-invasive option.
• Tumours close to critical structures where precision is essential.
• A need for a shorter overall treatment course.
• Limited metastases that may benefit from focused local treatment alongside systemic therapy.

Treatment Planning

Step 1: Consultation and Decision

The radiation oncologist reviews the diagnosis, imaging, biopsy results, and overall health. Where relevant, the case is discussed in a multidisciplinary tumour board with surgeons, medical oncologists, radiologists, and pathologists. The expected benefits, alternatives, and possible side effects are discussed with you, and consent is obtained.

Step 2: Simulation

Simulation is a planning session, not a treatment session. You lie on the treatment table in the exact position you will be in during treatment. Custom devices may be used to keep you still, such as a vacuum-bag mould, a body frame, or a face mask for upper-body treatments. Small marks may be made on your skin to help align the beams.

Step 3: Planning Scans

A planning CT scan is performed. For tumours that move with breathing, a 4D CT scan captures that movement. Sometimes MRI or PET imaging is added and merged with the CT to define the tumour more accurately. In some cases, small markers called fiducials may be placed near the tumour beforehand to help track it during treatment.

Step 4: Target and Organ Definition

The radiation oncologist outlines the tumour and the organs at risk on the planning scans. Safety margins are added to account for small movements and any uncertainty.

Step 5: Dose Planning

Medical physicists and dosimetrists design the beam arrangement, the dose delivered, and the number of fractions. Different combinations are tested until a plan is reached that delivers the prescribed dose to the tumour while keeping doses to nearby healthy tissue within accepted safety limits, as recommended by professional bodies such as the American Association of Physicists in Medicine.

Step 6: Plan Review and Quality Checks

The plan is reviewed by the radiation oncologist and physicist. Quality assurance tests confirm that the machine will deliver the dose as planned. Only then is the first session scheduled.

What Happens During Treatment

SBRT sessions take place in a treatment room similar to that used for other radiation therapies, though specifically equipped for stereotactic delivery. The course is usually one to five sessions, given daily or every other day, completed within one to two weeks.

A Typical Session

• You arrive and change into a gown if needed.
• The radiation therapists help you onto the treatment table in the same position used during simulation, using the same immobilisation devices.
• Imaging (such as a cone-beam CT) is performed to confirm the tumour's location. Small position adjustments are made.
• The therapists leave the room and monitor you on cameras and intercom from the control area.
• The treatment machine moves around you, delivering radiation from multiple angles. You will not see or feel the radiation.
• For tumours that move with breathing, you may be asked to hold your breath at intervals, or the machine may pause during certain breathing phases.

A session typically lasts between 30 and 60 minutes. Most of that time is spent on positioning and imaging; the actual radiation delivery is shorter. You can usually go home the same day and resume light activities.

Side Effects and How They Are Managed

SBRT is generally well tolerated, partly because of its precision and partly because the total number of sessions is small. Side effects depend strongly on the site being treated, the dose, and the volume of healthy tissue exposed. Side effects are usually classified as early (during or within weeks of treatment) and late (months to years later).

Common Early Side Effects

• Fatigue, often mild to moderate.
• Mild skin changes in the treated area, such as redness or dryness.
• Local soreness or swelling in or near the treated area.

Site-Specific Side Effects

• Lung SBRT: cough, chest discomfort, shortness of breath; in a minority of patients, inflammation of the lung tissue (radiation pneumonitis).
• Liver SBRT: abdominal discomfort, nausea, mild changes in liver function tests; in rare cases, more significant liver injury.
• Prostate SBRT: temporary urinary frequency, urgency, or weak stream; bowel changes such as urgency or loose stools; effects on erectile function in some patients over time.
• Pancreatic and abdominal SBRT: nausea, loss of appetite, abdominal discomfort, and in some cases bowel side effects.
• Spinal SBRT: local soreness, temporary worsening of pain (a “pain flare”) in the first days, and a small risk of vertebral compression fracture later.

Rare but Important Complications

• Radiation pneumonitis or fibrosis in the lung.
• Injury to the chest wall or rib fractures with some lung SBRT plans.
• Damage to nearby structures such as the bowel, oesophagus, large blood vessels, or the spinal cord. Planning aims to keep these doses below recognised safety thresholds.
• Secondary cancers from radiation, a small long-term risk associated with any radiation therapy.

Managing Side Effects

The care team monitors side effects during and after treatment. Practical steps that are commonly advised include:

• Resting when tired, and pacing daily activities.
• Keeping skin in the treated area clean and using moisturisers as recommended by the team.
• Staying well hydrated and eating regularly, with dietary advice where relevant.
• Taking prescribed medications for pain, nausea, or other symptoms.
• Reporting new or persistent symptoms early, especially shortness of breath, fever, severe pain, or bowel and urinary changes.

Response and Monitoring

Tumours treated with SBRT often shrink slowly. Unlike surgery, where the tumour is removed at a single moment, radiation works over time. It can take months for imaging to show a clear response, and some treated areas may remain visible on scans without containing active cancer.

Follow-up Schedule

Follow-up is usually planned by the radiation oncologist together with the medical oncologist and any other specialists involved. A typical schedule includes:

• A first follow-up visit a few weeks after treatment to check on side effects.
• Follow-up imaging (CT, MRI, or PET, depending on the cancer type) at intervals of about 3 to 6 months in the first one to two years, then less frequently.
• Blood tests where relevant, such as PSA tracking after prostate SBRT or liver function tests after liver SBRT.
• Long-term surveillance to detect recurrence and to monitor for late side effects.

Outcomes

Outcomes vary by cancer type, stage, and the goal of treatment. In general:

• For early-stage non-small cell lung cancer in patients who cannot have surgery, SBRT achieves high rates of local control of the treated tumour, and current guidelines describe it as a standard option in this setting.
• For prostate cancer, SBRT in five sessions is included in major guidelines as one accepted form of radiation therapy.
• For oligometastatic disease, studies have shown that adding SBRT to systemic therapy can delay progression in selected patients.
• For liver, spine, and adrenal tumours, SBRT can achieve durable local control in many cases.

Personalised estimates of expected response and risk should come from your own radiation oncologist after reviewing your scans and pathology. Numbers reported in studies do not translate directly to any single patient.

Combining SBRT with Other Treatments

SBRT is rarely the only treatment used in cancer care. It is often part of a wider plan that may include surgery, chemotherapy, immunotherapy, targeted therapy, or hormone therapy.

• With systemic therapy. SBRT is increasingly used together with chemotherapy, immunotherapy, or targeted therapy, especially in oligometastatic disease. The timing of SBRT around these treatments is planned carefully by the team.
• After or instead of surgery. For some early-stage tumours, SBRT is offered when surgery is not suitable, or as an alternative discussed with the patient.
• With hormone therapy. In prostate cancer, SBRT may be combined with androgen deprivation therapy in selected patients.
• For symptom control. SBRT can be used to treat painful or compressing metastases, particularly in the spine.

How these treatments fit together is a decision for the multidisciplinary cancer team in light of the specific diagnosis.

Living During and After Treatment

Because SBRT is non-invasive and the course is short, many people continue most of their daily activities during treatment, with adjustments for fatigue and travel to the centre. Driving home after sessions is usually fine, though some people prefer not to drive on treatment days.

During the Treatment Course

• Plan extra rest. Even a short course can cause noticeable fatigue.
• Keep a simple diary of symptoms to share with the care team.
• Continue prescribed medications unless your oncologist tells you otherwise.
• Eat regular, balanced meals and stay hydrated.
• Avoid applying creams, perfumes, or strong soaps to the treated skin unless the team has approved them.

In the Weeks After Treatment

• Fatigue often peaks one to two weeks after the final session and improves gradually.
• Site-specific symptoms (such as a mild cough after lung SBRT or urinary changes after prostate SBRT) may take several weeks to settle.
• Most people return to their usual routines within days to a few weeks, depending on the site treated and overall health.

Emotional Wellbeing

Living with cancer and going through any radiation treatment can be emotionally demanding, even when the treatment itself is short. Anxiety before scans (sometimes called “scanxiety”) and worry about recurrence are common. Cancer centres often have access to counselling, support groups, and palliative care services that focus on symptom and quality-of-life support alongside cancer treatment. Asking for this support is reasonable at any point in the journey.

SBRT in Special Situations

Older Adults

SBRT is particularly relevant for older adults who may not be candidates for surgery because of heart, lung, or other health conditions. The short treatment course is often easier to tolerate than weeks of daily radiation. Decisions take into account overall health, life expectancy, and treatment goals.

Patients with Limited Lung Function

For early lung cancer in patients whose lungs cannot tolerate surgery, lung SBRT is described in major guidelines as a standard option. Careful planning accounts for the volume of healthy lung receiving radiation.

Reirradiation

If a tumour returns in or near a previously treated area, SBRT may sometimes be considered. This requires careful review of prior radiation doses to nearby healthy tissue and is a specialist decision.

Children

SBRT is used much less often in children than in adults. Paediatric cancer is usually treated in specialist centres with treatment plans built around the developing body. When radiation is needed for a child, the choice of technique — including whether stereotactic methods are used — is made by a paediatric radiation oncology team.

Questions to Discuss with Your Radiation Oncologist

Bringing a written list of questions to consultations often helps. Useful topics include:

• Why is SBRT being considered for my situation, and what are the alternatives?
• What is the goal of treatment — cure, long-term control, or symptom relief?
• How many sessions will I need, and over how many days?
• Which side effects are most relevant for my treatment site, and how will they be managed?
• How will response be monitored, and on what schedule?
• How does SBRT fit with my other treatments, such as chemotherapy, immunotherapy, or hormone therapy?
• What signs or symptoms should prompt me to contact the team between visits?

Frequently Asked Questions

Is SBRT the same as CyberKnife, Gamma Knife, or TrueBeam?

These are brand names of machines used to deliver stereotactic radiation. SBRT is the type of treatment; the machine is the tool that delivers it. Different platforms can all deliver SBRT, though their technical details differ. Gamma Knife is generally used for the brain. The choice of machine depends on what the centre uses and what is suitable for the tumour site.

Is SBRT painful?

The radiation itself cannot be felt during delivery. Some patients feel discomfort from lying still in the treatment position or from immobilisation devices. Pain that develops afterwards depends on the treatment site.

Will I be radioactive after SBRT?

No. External beam radiation, including SBRT, does not make you radioactive. There is no need to avoid contact with family members, including children or pregnant women, after sessions.

How many SBRT sessions will I need?

Most courses are between one and five sessions delivered within one to two weeks. The exact number depends on the cancer type, the tumour location, and the dose plan.

Can SBRT replace surgery?

For some early-stage tumours, particularly in patients who cannot safely have surgery, SBRT is included in major guidelines as a recognised alternative. For other situations, surgery remains the preferred approach. Whether SBRT is suitable instead of surgery is a clinical decision made with the cancer team.

Can SBRT be repeated if the cancer comes back?

Sometimes. Reirradiation with SBRT is possible in selected cases, but it depends on the doses previously received by nearby healthy tissue. This is a specialist decision.

How soon will I know if SBRT has worked?

Tumours often shrink slowly after radiation, and imaging may take months to show clear changes. The follow-up schedule is designed to detect both response and any new problems over time.

Can I work during SBRT?

Many people continue working, especially in less physically demanding roles, though fatigue and travel to the centre may require some adjustment. The radiation oncology team can advise based on your situation.

Does SBRT cause hair loss?

SBRT only causes hair loss in the small area where the radiation beams enter or exit the skin, and only if that area carries hair. It does not cause the generalised hair loss associated with some chemotherapy.

Is SBRT safe in older patients?

Age alone is not usually a reason to avoid SBRT. The short course and non-invasive nature make it particularly relevant for older patients who cannot tolerate surgery. Overall health, life expectancy, and treatment goals guide the decision.

Conclusion

Stereotactic body radiation therapy has become an established part of modern radiation oncology. By combining advanced imaging, motion management, and precise beam delivery, SBRT makes it possible to give a high dose of radiation to a small tumour in just a few sessions while protecting surrounding healthy tissue.

For people with early-stage cancers who cannot have surgery, for selected prostate, liver, lung, spinal, and adrenal tumours, and for patients with a limited number of metastases, SBRT is one of the options that modern guidelines now describe alongside surgery and other forms of radiation. Whether it is the right choice depends on detailed imaging, pathology, and an honest conversation with the radiation oncologist and the wider cancer team.

Understanding what SBRT is, how it is planned and delivered, what side effects to watch for, and how response is monitored can help make the treatment course feel less unfamiliar and support clearer conversations with the doctors who will be guiding the care.