Stereotactic 3D radiotherapy (CyberKnife)

Indications

① Typical scenarios most suitable for CyberKnife

• Lesions that move significantly with respiration or organ motion (e.g., some lung, liver, or peri-pancreatic lesions).

• Lesions adjacent to critical structures requiring precise dose control (e.g., intracranial, paraspinal regions).

• Residual or recurrent lesions after previous treatment.

② Common indications

• Head and neck: primary tumors, re-irradiation.

• Lung: early and advanced primary lung cancer, lung metastases.

• Pancreas: patients unsuitable for surgery, preoperative or postoperative boost radiotherapy.

• Intracranial: brain metastases, primary tumors, trigeminal neuralgia, arteriovenous malformations.

• Liver: liver metastases, primary liver cancer unsuitable for surgery.

• Spine: spinal metastases, benign tumors, spinal arteriovenous malformations.

• Prostate: low- and intermediate-risk prostate cancer, monotherapy.

Technical Advantages

① Non-invasive, high-precision treatment: The CyberKnife uses omnidirectional central focusing and three-dimensional dose stacking, allowing the radiation to conform closely to the tumor's shape and position. With image-guided correction, it can achieve millimeter-level, and when necessary, submillimeter precision. Treatment does not require surgery or anesthesia, making the process more comfortable.

② Real-time image guidance and dynamic alignment: The system tracks the tumor dynamically using real-time imaging, ensuring each dose is delivered precisely to the target while minimizing exposure to surrounding healthy tissues.

③ Adaptation to tumor motion: For lesions that move with respiration (such as in parts of the lung, liver, or around the pancreas), the CyberKnife tracks the patient's position, tumor location, and respiratory motion in three dimensions and adjusts the beam direction in real time to match the tumor's actual position.

④ Precision near intracranial and spinal lesions: For tumors close to brain tissue, cranial nerves, or the spinal cord, treatment plans are designed with high precision to maximize protection of critical structures while adhering to strict dose constraints.

⑤ Concentrated treatment courses suitable for outpatient care: The CyberKnife is often used in regimens with a small number of sessions. Most patients can complete the treatment on an outpatient basis. The number of sessions is individualized based on tumor size, location, and tolerance of surrounding organs (commonly 1--5 sessions, with more in some cases).

Why Choose Jinshazhou Hospital?

In 2019, our hospital introduced the sixth-generation Accuray CyberKnife M6 system, the first of its kind in China, as a key piece of equipment at our Radiation Oncology Center. In 2020, the hospital obtained the necessary authorization to provide radiation-based medical services and performed its first CyberKnife treatment on July 10 of the same year. In October 2026, the system was upgraded to CyberKnife S7, incorporating the next-generation VOLO automated optimization engine to provide cancer patients with more efficient and precise robotic stereotactic radiosurgery and stereotactic body radiation therapy (SRS/SBRT).

Based on the CyberKnife S7 and other advanced radiotherapy platforms, we follow the principle of "individualized approach first": during MDT discussions, it is first assessed whether the patient is suitable for radiotherapy, the role and timing of radiotherapy in the overall treatment are determined, and coordination with surgery, interventional procedures, and systemic therapy is ensured. The radiotherapy team develops an individualized plan considering tumor location, proximity to critical structures, organ motion, and dose constraints, selecting the most appropriate platform and technical strategy rather than applying a "one-size-fits-all" approach.

The entire process is controlled through a closed-loop quality system: pre-treatment evaluation, plan verification, imaging-based corrections during therapy, and follow-up checks. This ensures that treatment is stable and manageable. Patients receive a comprehensive pathway: imaging evaluation, plan discussion, treatment planning, and therapy execution within the hospital, with integration with surgery, interventional, and systemic treatments when necessary. Key steps are under control, the treatment path is clear, and therapy is safe and reliable.

Technical Definition

The CyberKnife is a robotic stereotactic radiosurgery system, sometimes described as a “3D stereotactic radiosurgery robot.” Our hospital's sixth-generation CyberKnife M6 has been upgraded to the CyberKnife S7 system. Equipped with a high-precision six-axis robotic arm, it delivers radiation from multiple directions around the target with submillimeter precision (±0.06 mm isocentric accuracy). Its proprietary real-time image tracking technology continuously monitors tumor movement during treatment and automatically adjusts beam targeting to compensate for respiratory motion and changes in patient positioning, ensuring that radiation remains precisely focused on the tumor.
The VOLO automated optimization engine serves as the “intelligent brain” of the CyberKnife S7 system. Using advanced inverse optimization algorithms, together with the Accuray Precision treatment planning system and the iDMS data management platform, it enables intelligent treatment plan generation and streamlined plan management.

Mechanism of Action / Working Principle

① Omnidirectional Central Focusing and Three-Dimensional Dose Shaping

CyberKnife belongs to the category of stereotactic radiosurgery (SRS/SBRT). Its linear accelerator is mounted on a high-precision robotic arm, which can deliver fine beams from multiple angles around the patient. According to the treatment plan, these beams are superimposed within the tumor to create a three-dimensional dose distribution and precise shaping, concentrating the dose in the target while reducing exposure to surrounding healthy tissues. The radiation primarily damages tumor cell DNA, inhibiting replication and proliferation to achieve therapeutic effects.

② Image Guidance and Tracking Correction

CyberKnife uses imaging before and during treatment to verify and correct positioning. For lesions affected by respiratory or organ motion, strategies such as fiducial tracking or direct tumor tracking can be applied, allowing real-time adjustment of the beam according to tumor movement to ensure the radiation accurately matches the actual tumor position.

③ Smart Optimization and Automation Program

The VOLO automated optimization engine uses advanced inverse optimization algorithms to automatically determine beam paths and weights based on prescribed target doses and dose constraints for organs at risk. It can generate a high-quality, individualized treatment plan in approximately 15 minutes, potentially increasing planning optimization speed by around 90%. This significantly reduces treatment plan turnaround times for patients with rapidly progressing tumors or those traveling to Guangzhou from other regions who need to begin treatment as soon as possible.

④ AI-Powered Real-Time Tracking and Motion Compensation (Synchrony)

For tumors that move with respiration, the upgraded system uses Synchrony® AI real-time tumor tracking technology to continuously monitor tumor displacement and automatically adjust beam direction during treatment, without requiring patients to hold their breath for extended periods. This is also one of the key factors enabling individual treatment sessions to be shortened to approximately 15 minutes.

Treatment Procedure

① Assessment and preparation: The radiation oncologist evaluates the patient's condition, previous treatment history, and imaging to determine suitability for CyberKnife treatment and clarify treatment goals and timing; if necessary, an MDT discussion is held to coordinate with surgery, interventional therapy, or systemic treatment.

② Positioning and imaging acquisition: The patient is immobilized according to the treatment site, and a planning CT is performed (with MRI/enhanced CT or 4D-CT if needed) to obtain precise images for treatment planning. For lesions affected by organ motion, some patients may require implantation of fiducial markers (e.g., gold markers) under image guidance to support tracking strategies.

③ Target delineation and plan design: The radiation oncologist delineates the target and critical organs to protect; the medical physicist optimizes beam paths and dose distribution in the planning system and develops appropriate tracking/correction strategies; the plan is reviewed and approved by the team.

④ Treatment delivery: Before each session, image verification and positioning correction are performed; during treatment, the system monitors position using image guidance and applies necessary corrections/tracking, delivering multi-angle irradiation as planned. In most cases, anesthesia is not required, and treatment can be completed on an outpatient basis (subject to individual assessment).

⑤ Follow-up and review: After treatment, imaging and relevant tests are reviewed according to the follow-up schedule to assess efficacy and monitor reactions; any discomfort or worsening reaction should be promptly reported to the physician for management.

Frequently Asked Questions

① How many treatment sessions are needed with CyberKnife?

Answer: CyberKnife usually uses a small number of sessions, with many treatment plans completed in 1--5 sessions. The exact number is determined based on lesion size, location, respiratory influence, and tolerance of surrounding organs. The physician will create an individualized plan and explain the treatment schedule in advance.

② Does CyberKnife treatment cause pain?

Answer: CyberKnife treatment is completely non-invasive and involves no surgical incision, so it usually does not cause noticeable pain. The patient only needs to lie still on the treatment bed. Individual pain perception may vary, and in very rare cases, slight discomfort may occur due to tumor location or high sensitivity to pain.

③ Are there side effects from CyberKnife treatment?

Answer: Due to its high precision and non-invasive nature, CyberKnife has minimal side effects. Most patients experience no significant discomfort after treatment, though some may have mild skin reactions or temporary fatigue.

④ How soon can normal activities be resumed after treatment?

Answer: Most patients can resume daily activities on the same day or the next day after treatment. A few may experience temporary fatigue or minor discomfort, which typically resolves after a day or two of rest.

⑤ What precautions should be taken during and after treatment?

Answer: Skin care is essential during radiotherapy. Patients should follow medical guidance for cleansing, moisturizing, sun protection, and avoiding irritation. After the treatment course, follow-up should be performed as instructed, maintaining a regular schedule and moderate activity. Any significant discomfort or worsening reaction should be reported to a physician or nurse for assessment and management.

Typical Case

① Case 1:

Patient: Female, 10 years old

Diagnosis: Malignant brain tumor (glioma)

Symptoms: Weakness in legs and arms, unclear speech

CyberKnife treatment started on 2020-06-14, radiation dose PTV 25 Gy / 5 Gy / 5 fractions

At 2 months post-treatment, follow-up imaging showed slight reduction of the brainstem tumor. The patient regained consciousness, speech improved significantly, and limb movement gradually returned to normal.

② Case 2:

Patient: Male, 67 years old

Secondary malignant brain tumor

Treatment with CyberKnife started on 2020-08-03, with a prescribed dose of 95% GTV DT15Gy delivered in 3 fractions of 5Gy each.

At 3 months post-treatment, imaging showed significant tumor reduction compared to previous scans.

③ Case 3:

Patient: Female, 46 years old

Diagnosis: Liver cancer

Treatment plan: 4D simulation and localization; lesions in segments S2 and S3 treated with DT 50 Gy / 10 Gy per fraction / 5 fractions.

Pre-treatment MRI at our hospital on 2020-12-06:

1. Multiple nodules in liver segments S2, S3, and S5; high possibility of small liver cancer.

2. Liver segment S6 hemangioma.

Follow-up MRI on 2021-04-14:

1. Post-comprehensive liver cancer treatment changes; lesions significantly smaller than before.

2. Gallbladder adenomyomatosis, largely unchanged.