STEREOTACTIC RADIOSURGERY (SRS)
AND SBRT / SABR
SRS, or stereotactic radiosurgery, is a precise radiation treatment that delivers high-dose beams to tumors and brain lesions while minimizing exposure to healthy tissue.
analyticsAt a Glance
- check_circleDelivers high-dose, precisely targeted radiation in 1โ5 sessions
- check_circleBrain metastases, AVM, acoustic neuroma, and early lung cancer indications
- check_circleSystems include Gamma Knife, CyberKnife, and linear accelerator-based SBRT
- check_circleNon-invasive โ no incision, no general anaesthesia required
What Are SRS and SBRT? The Key Distinction
SRS and SBRT are the same physical technique โ high-precision, ablative radiation delivered in 1โ5 fractions. The only difference is anatomical location: SRS treats intracranial targets; SBRT (also called SABR) treats extracranial targets.
โBy achieving millimeter-level precision and ablative dose levels, SRS and SBRT achieve local control rates equivalent to surgery for many tumor types โ without incision, anesthesia, or prolonged recovery.โ
SRS โ Stereotactic Radiosurgery
High-dose radiation delivered to intracranial targets: brain metastases, meningioma, acoustic neuroma, AVM, glioblastoma boost, trigeminal neuralgia. Typically 1โ3 fractions. Gamma Knife, CyberKnife, and LINAC-based VMAT systems are all used.
SBRT / SABR โ Stereotactic Body Radiotherapy
Ablative radiation for extracranial targets: lung, liver, spine, prostate, kidney, adrenal, lymph nodes, and oligometastases. Typically 3โ8 fractions. Requires 4D respiratory management for lung and liver; real-time tracking on CyberKnife or gating on LINAC systems.
Technology Platforms: Gamma Knife, CyberKnife, TrueBeam, and Proton SRS
Three distinct engineering approaches deliver SRS and SBRT. Understanding each helps patients ask informed questions about which system their treating center uses and why.
Gamma Knife (Elekta) โ Gold Standard for Intracranial SRS
192 cobalt-60 sources converge on a focal point with the sharpest dose gradient in SRS: dose drops 50% just 2โ3mm outside the target. Intracranial-only; cannot treat body. Available at Beijing Tiantan Hospital, Fudan Huashan Hospital, Apollo, and Fortis in India.
CyberKnife (Accuray) โ Robotic SRS and SBRT
A miniature LINAC on a 6-axis robotic arm delivers beams from hundreds of non-coplanar directions with sub-millimeter accuracy. Real-time respiratory tracking (Synchrony) allows continuous tumor following during breathing โ ideal for lung and liver SBRT. Treats both brain and body.
LINAC-Based SBRT โ TrueBeam, Edge, Versa HD
Gantry-mounted LINACs with VMAT, CBCT image guidance, and flattening-filter-free (FFF) mode deliver SBRT at up to 10ร conventional dose rate. Most widely deployed technology in China and India. Varian TrueBeam/Edge and Elekta Versa HD are the primary systems.
Proton SRS and SBRT
Bragg peak physics delivers near-zero dose beyond the tumor โ especially valuable for pediatric brain tumors and spine SBRT. China is second globally in proton capacity (SPHIC Shanghai, NCC Beijing). India: Apollo Hospitals Hyderabad. Cost: USD 8,000โ20,000 in China/India vs USD 40,000โ120,000 in the US.
SRS & SBRT by the Numbers
- 1โ5Fractions (vs 28โ42 for conventional radiation)
- 85โ97%3-year local control for Stage I NSCLC
- 28 monthsMedian OS in SABR-COMET oligometastatic trial (vs 13 months)
- 80โ90%Cost saving vs US pricing at China/India centers
- 17.7% vs 0%5-year overall survival in SABR-COMETLong-term follow-up showed a clear tail-of-the-curve benefit, with 17.7% of patients alive at 5 years after SABR versus 0% in the control arm.
- 92%1-year local control for brain metastases with SRSSRS routinely delivers very high local control in brain metastases while avoiding the cognitive burden of whole-brain radiation in many patients.
SRS for Brain Metastases: The Evidence That Changed Practice
Brain metastases โ occurring in 20โ40% of cancer patients โ represent the most extensively evidence-supported SRS indication. Randomized trial data has established SRS alone (without WBRT) as the standard for patients with 1โ10 brain metastases and good performance status.
SRS Alone vs WBRT โ The Neurocognitive Advantage
Multiple Phase III trials (JCOG 0504, N0574, N107C) show no survival difference between SRS alone and SRS + WBRT for 1โ4 metastases, but significantly better cognitive function preservation with SRS alone at 3โ6 months. WBRT is now reserved for numerous (>10) metastases and leptomeningeal disease.
Up to 10 Brain Metastases: The JLGK0901 Evidence
The Japanese JLGK0901 prospective trial established non-inferior survival for SRS treating 5โ10 vs 2โ4 brain metastases, provided total tumor volume is below 15 mL. Chinese and Indian SRS centers routinely treat 5โ10 metastases in a single Gamma Knife or CyberKnife session.
CNS-Penetrant Systemic Therapies: When to Defer SRS
For EGFR-mutant NSCLC (osimertinib: 70โ90% CNS response rate) and ALK-rearranged NSCLC (alectinib: 80โ90% CNS response), specialist centers may defer SRS in favor of systemic therapy and reserve SRS for salvage or consolidation.
Key SBRT Indications: Lung, Liver, Spine, and Prostate
SBRT has established or emerging curative-intent roles across multiple extracranial sites. Evidence strength varies by indication.
Lung SBRT (Stage I NSCLC)
The established standard for inoperable Stage I NSCLC: RTOG 0236 showed 97.6% 3-year local control with 3-fraction SBRT. For operable patients, ongoing Phase III trials (SABR-STAR, VALOR) are evaluating SBRT vs lobectomy. Central lung tumors require 5โ8 fraction risk-adapted protocols.
Liver SBRT (HCC and CRLM)
SBRT achieves 80โ90% 2-year local control for HCC โ with advantages over RFA for perivascular tumors and coagulopathic patients. A Korean RCT (JAMA Oncology, 2022) showed SBRT superior to TACE for local progression-free survival (75% vs 46%). Also effective for colorectal liver metastases near major vessels.
Spine SBRT (Spinal Metastases)
Delivers 16โ24 Gy in 1โ3 fractions with 85โ95% local control โ dramatically superior to conventional 8 or 20 Gy palliative radiation. Particularly effective for radioresistant histologies (RCC, melanoma, CRLM). Separation surgery required for epidural disease before SBRT.
Prostate SBRT (5 Fractions)
The PACE-B Phase III trial confirmed 5-fraction SBRT (35โ40 Gy) as equivalent to conventional radiation for low/intermediate-risk prostate cancer with non-inferior quality of life. Radiobiologically superior due to prostate cancer's low alpha/beta ratio (~1.5 Gy), achieving BED equivalent to 79 Gy conventional.
SBRT for Oligometastatic Disease: The SABR-COMET Evidence
Oligometastatic disease (1โ5 metastases in 1โ3 organs) is where SBRT has the greatest potential to transform stage IV outcomes โ converting incurable to potentially curable or achieving durable long-term remission.
โSABR-COMET: Adding SBRT to all oligometastatic sites reduced the hazard of death by 53% โ median OS 28 vs 13 months, with 17.7% alive at 5 years vs 3.2% in the control arm.โ
SABR-COMET Trial Results (Lancet 2019 / JAMA 2020)
99 patients with 1โ5 oligometastases randomized to palliative standard of care ยฑ SBRT to all sites. SBRT arm: median OS 28 months vs 13 months (HR 0.47, p=0.006); 5-year OS 17.7% vs 3.2%. Mixed histologies (colorectal, lung, breast, prostate, pancreas) โ all benefited.
Confirmed in Disease-Specific Trials
ORIOLE and STOMP trials confirmed progression-free survival benefit for SBRT in oligometastatic prostate cancer. SINDAS (China, JAMA Oncology 2020) showed OS benefit for SBRT in oligometastatic EGFR-mutant NSCLC (25.5 vs 17.4 months). SBRT + immunotherapy combination trials are ongoing.
SBRT Local Control Rates by Indication
Local control rates from major prospective trials and registry data for key SBRT indications.
Stage I NSCLC (RTOG 0236)
Hepatocellular Carcinoma (SBRT vs TACE RCT)
Spine SBRT (All Histologies)
Oligometastatic Disease (SABR-COMET)
SRS/SBRT Technology Comparison
Key differences between Gamma Knife, CyberKnife, LINAC-based systems, and proton therapy.
| System | Brain SRS | Body SBRT | Key Advantage | China / India Availability |
|---|---|---|---|---|
| Gamma Knife (Elekta) | Gold standard | No | Sharpest intracranial dose gradient; 50% dose drop in 2โ3mm | Beijing Tiantan, Fudan Huashan; Apollo, Fortis India |
| CyberKnife (Accuray) | Yes | Yes โ all sites | Real-time respiratory tracking (Synchrony); non-coplanar beams | Both countries โ major cancer centers |
| TrueBeam / Edge (Varian) | Yes | Yes โ all sites | Fastest FFF delivery; widest deployment globally | Both countries โ most widely deployed |
| Versa HD (Elekta) | Yes | Yes โ all sites | Agility MLC; CBCT + surface guidance | Both countries |
| Proton SRS/SBRT | Yes | Yes | Bragg peak; near-zero exit dose; best for pediatric/spine | China: SPHIC, NCC Beijing; India: Apollo Hyderabad |
SBRT vs Surgery: When to Choose Which
SBRT Advantages
- No incision, anesthesia, or hospitalizationOutpatient treatment; return to normal activities within days.
- Safe for medically inoperable patientsSevere COPD, cardiac disease, or poor performance status that precludes surgery.
- Treats multiple sites simultaneouslySBRT can address all oligometastatic sites in one treatment course; surgery cannot.
- Equivalent local control for peripheral Stage I NSCLCPhase II data shows comparable outcomes to lobectomy for inoperable patients.
Surgery Advantages
- Provides pathological tissue for diagnosis and molecular profilingCritical when histology confirmation or genomic testing is needed.
- Definitive treatment for resectable early-stage diseaseLobectomy remains standard for operable Stage I NSCLC โ SBRT equivalence in operable patients awaits Phase III data.
- Direct visualization and lymph node stagingSurgical resection allows nodal assessment that imaging may miss.
SRS & SBRT Cost Comparison: China, India, and USA
Approximate costs for key SRS and SBRT procedures at specialist centers in China, India, and the United States.
| Procedure | China (USD) | India (USD) | USA (USD) |
|---|---|---|---|
| SRS โ single brain met (Gamma Knife) | 3,000โ7,000 | 2,500โ6,000 | 20,000โ40,000 |
| SRS โ multiple brain mets (1 session) | 4,000โ9,000 | 3,000โ8,000 | 25,000โ50,000 |
| Lung SBRT (3โ5 fractions, Stage I NSCLC) | 4,000โ9,000 | 3,000โ7,500 | 20,000โ50,000 |
| Liver SBRT (3โ6 fractions, HCC or CRLM) | 4,000โ9,000 | 3,000โ7,500 | 20,000โ50,000 |
| Spine SBRT (3-fraction, single level) | 3,000โ7,000 | 2,500โ6,000 | 15,000โ35,000 |
| Prostate SBRT (5 fractions) | 4,000โ9,000 | 3,000โ7,500 | 15,000โ35,000 |
| Oligometastatic SBRT (3โ5 sites) | 6,000โ15,000 | 5,000โ12,000 | 25,000โ70,000 |
| Proton SRS/SBRT | 8,000โ20,000 | 8,000โ18,000 | 40,000โ120,000 |
| Carbon ion SBRT (HCC/skull base, SPHIC only) | 15,000โ30,000 | Not available | Not widely available |
SRS & SBRT Centers in China and India
China and India collectively have the largest SRS and SBRT infrastructure in Asia โ offering the same technology as the US's best centers at 80โ90% lower cost.
China: Key Centers
Beijing Tiantan Hospital (largest Chinese SRS series โ brain mets, meningioma, GBM); Shanghai Proton & Heavy Ion Center โ SPHIC (proton + carbon ion, world-unique); National Cancer Center Beijing (largest Chinese SBRT dataset); Fudan University Shanghai Cancer Center (lung, liver, prostate, spine SBRT + immunotherapy trials); Sun Yat-sen University Cancer Centre Guangzhou (NPC boost, oligometastatic NSCLC).
India: Key Centers
Tata Memorial Centre Mumbai (public sector, full SRS/SBRT range); Apollo Cancer Centres Chennai/Hyderabad/Delhi (Gamma Knife, CyberKnife, TrueBeam/Edge + proton at Hyderabad); HCG Cancer Centre Bangalore (largest CyberKnife series in India); Fortis Memorial Research Institute Gurugram; AIIMS Delhi (government-sector advanced SBRT).
Explore Related SRS & SBRT Topics
20 dedicated support pages cover specific SRS and SBRT topics in depth.
- What is SRS and how is it different from regular radiation?
- Gamma Knife vs CyberKnife vs TrueBeam: How to Choose
- SRS for Brain Metastases: The Evidence That Changed Standard of Care
- SRS vs WBRT: Understanding the Neurocognitive Trade-Off
- SRS for Acoustic Neuroma: Radiation Over Surgery
- Spine SBRT: How Radiation Treats Spinal Metastases Without Surgery
- SBRT for Stage I Lung Cancer: The Evidence Comparing It to Surgery
- Liver SBRT for HCC and Liver Metastases
- Prostate SBRT (5 Fractions): The PACE Trial Explained
- Oligometastatic Disease and SBRT: The SABR-COMET Trial
- SBRT Combined with Immunotherapy: The Abscopal Effect
- SRS and SBRT Costs in China and India: Detailed Comparison
- Accessing SRS and SBRT in China or India through CancerFax
Frequently Asked Questions About SRS and SBRT
About the Procedure
What is stereotactic radiosurgery?
Stereotactic radiosurgery, or SRS, is a non-surgical technique that delivers a highly focused, high dose of radiation to a tumor with extreme precision, typically in one to a few sessions. Despite the name, no actual surgical cutting takes place. Instead, multiple precisely aimed radiation beams converge on the tumor from different angles, concentrating a powerful dose at that single point while minimizing the radiation reaching surrounding healthy tissue.
Advances in radiation therapy, including stereotactic radiosurgery and fractionated stereotactic radiotherapy, have significantly improved the precision and efficacy of local treatment for brain metastases while minimizing damage to surrounding healthy brain tissue. It is most widely used for tumors in the brain, where its precision matters most given how sensitive surrounding tissue is.
How is SRS different from standard radiotherapy or surgery?
Standard radiotherapy usually spreads a lower dose of radiation over many sessions across a broader area, while SRS concentrates a much higher dose into one or a few sessions aimed very precisely at the tumor itself. Unlike surgery, there is no incision, no general anesthesia in most cases, and recovery is typically much faster. SRS can also reach tumors in locations that would be risky or impossible to access surgically, which is part of why it has become central to managing brain metastases.
A related technique, fractionated stereotactic radiotherapy, spreads the high-precision dose over several sessions instead of one, which can help with larger tumors. As one study notes, FSRT administers radiation over several sessions, typically spaced 1 to 3 days apart, improving local control of larger brain metastases to 80 to 90% while reducing adverse events.
Efficacy and outcomes
How effective is SRS for cancer that has spread to the brain?
SRS has strong, well-documented outcomes for brain metastases, though results vary by the cancer's primary site and how much disease is present. In breast cancer that has spread to the brain, a meta-analysis of over 1,200 patients across 16 studies found a median survival duration of 13.1 months and a pooled 1-year overall survival rate of 53.1% after SRS treatment, alongside a relatively low rate of acute side effects. Even patients with a large number of brain metastases can benefit.
In one study of patients with 16 or more brain metastases treated with SRS alone, those previously treated had a median overall survival of 19.8 months compared with 6 months in those newly diagnosed with that many metastases, showing that outcomes depend heavily on disease history and overall tumor burden rather than lesion count alone.
Can SRS cure cancer that has spread to the brain?
SRS is generally not described as a cure for metastatic cancer, since brain metastases reflect disease that has already spread from elsewhere in the body. Its real strength is in achieving strong local control, meaning it stops the treated tumor from growing while preserving brain function and quality of life better than older approaches like whole brain radiation. Research has also identified what most influences survival after SRS.
One large single-center study found that post-SRS new metastatic disease increased the risk of death by 31%, while local recurrence did not, meaning that the original treated tumor staying controlled matters less for survival than whether new metastases appear elsewhere. This underscores that SRS is one part of an overall cancer strategy, working alongside systemic treatment, rather than a stand-alone cure.
Treatment process
What does the SRS treatment process involve?
The process begins with detailed imaging, usually MRI and CT scans, to precisely map the tumor's location, size, and shape. Modern planning often uses specialized software for this. As one description of the treatment process notes, planning computed tomography and magnetic resonance imaging images are imported into specialized multi-metastases planning software and deformably registered, with gross tumor volumes expanded slightly to create planning target volumes.
The patient is then fitted with an immobilization device, often a custom mask, to keep their head perfectly still during treatment. The radiation is delivered in one session for smaller, simpler cases, or spread across two to five sessions for larger tumors or multiple lesions, with each session typically lasting under an hour.
What are the side effects of SRS?
SRS is generally well tolerated, especially compared to whole brain radiotherapy, with most patients experiencing few or only mild, temporary side effects such as fatigue, headache, or scalp irritation. A meta-analysis in breast cancer brain metastases found a relatively low rate of acute adverse events at 15.5%. The most specific risk to be aware of with SRS is a phenomenon called local treatment failure, where the treated tumor does not fully respond, or radiation necrosis, where the treated tissue reacts to the radiation.
One large study tracking lesion-level outcomes found that 15% of treated lesions demonstrated MRI findings concerning for local treatment failure, of which 12% demonstrated true local treatment failure and 3% had an adverse radiation effect. Quality of life tends to be well preserved after SRS, an important factor tracked in ongoing national patient registries.
Access and availability
Is SRS widely available?
Yes, SRS is a well-established, widely available treatment at major cancer centers and dedicated radiosurgery centers around the world, including leading hospitals in China and India. It requires specialized equipment, such as a Gamma Knife or linear accelerator-based system, along with a specially trained radiation oncology and neurosurgery team.
Current treatment guidelines support its use across a range of situations, recommending stereotactic radiosurgery as a standard option for brain metastases under three centimeters, and many centers now treat patients with multiple metastases in a single course using modern multi-lesion planning techniques.
How can CancerFax help patients access SRS?
CancerFax helps patients and families understand whether SRS is the right option for their specific situation, particularly when cancer has spread to the brain, and, where appropriate, connects them with experienced centers offering this treatment, including those with strong outcomes for the patient's specific primary cancer type.
This support can include reviewing the diagnosis, number and size of brain lesions, and prior treatment history, arranging expert second opinions, and coordinating the practical side of accessing care, including hospital communication, documentation, translation, and travel support. Because the right approach depends heavily on the number, size, and location of metastases as well as the primary cancer and overall treatment plan, the first step is always a thorough case review by the treating oncology and radiation oncology team.
How CancerFax Helps
CancerFax is a specialist cancer access and patient-navigation platform. We help patients and families understand their options, organise medical records, coordinate hospital communication, and support cross-border treatment planning where appropriate.
We help collect and organise reports, scans, pathology, biomarker results, and treatment history for structured case review.
We communicate with hospitals or trial teams to assess whether a case may be suitable for further screening.
We support appointment coordination, document submission, translation, and direct communication with international departments.
For international patients, we help with practical coordination โ travel planning, hospital admission guidance, and local support.
If this option is not suitable, we help explore other relevant treatments, clinical trials, or advanced care pathways.
From inquiry through to follow-up, our coordinators provide a single point of contact for the family.
CancerFax does not guarantee treatment access, eligibility, or clinical outcome. Our role is to help patients access accurate information, structured review, and appropriate specialist pathways.
Is SRS or SBRT Right for Your Situation? Let CancerFax Assess.
CancerFax reviews your tumor type, stage, metastatic burden, and prior treatment history to determine whether SRS or SBRT is evidence-based for your indication, then matches you with the right technology platform at the right center in China or India.
This content is for informational purposes only and does not constitute medical advice. All treatment decisions should be made in consultation with qualified radiation oncology specialists.