The Leading Treatment Option
In 2001 the CyberKnife® System received FDA clearance for treatment of tumors anywhere in the body that radiation was indicated. Since then CyberKnife users around the world have developed and continue to develop protocols for treating tumors in the brain, prostate, lungs, spine, liver, pancreas, and kidneys. On this page we’ll describe these applications, and how CyberKnife users have approached them. As these clinical developments evolve so will our treatment options; the evolution of the CyberKnife technology will be driven clinically so that patients continue to receive the best, least invasive radiosurgical treatment available.
The most common brain tumors are metastases and malignant (e.g., astrocytomas) or benign (e.g., meningiomas, acoustic neuromas) primary tumors. Brain cancer surgery and chemotherapy are established brain cancer treatments, but for decades radiotherapy and radiosurgery have also been important brain cancer treatments. The goals of radiosurgery are symptom relief, local tumor control, and potentially longer survival.
Using the CyberKnife System to Treat Brain Tumors:
Due to the high rates of recurrence of resected metastatic disease, brain cancer surgery has often been followed by conventional radiotherapy. The CyberKnife® System can provide localized focused radiation treatment after brain cancer surgery without the morbidity caused by conventional radiotherapy. Non-isocentric radiation beam delivery (i.e., beams that do not have to converge on a single point) allows the dose distribution to conform to even irregularly shaped tumors. The accuracy of the CyberKnife System has been shown to be sub-millimetric, allowing the delivery of large doses while avoiding critical structures. Frameless, non-invasive radiosurgery with the CyberKnife System can be delivered in a single fraction or multiple fractions (sessions). This allows the dose to be spread over 2-5 sessions which may reduce the risk of damage to sensitive structures such as the cranial nerves and the eye. The safety and efficacy of the CyberKnife System for the treatment of metastatic intracranial lesions is well established. Published reports indicate high rates of tumor control (91%) for intracranial tumor patients with low complication rates. Benign intracranial tumors also can be effectively treated with the CyberKnife System. A 98% tumor control rate and a 74% hearing preservation rate has been reported for 61 acoustic neuroma patients treated with the CyberKnife between 1999 and 2001. Patients with perioptic tumors have responded well to fractionated radiosurgery with the CyberKnife System.
Prostate cancer surgery (radical prostatectomy) has been the most common approach to treating prostate cancer, although brachytherapy (low dose rate with permanent seed implant or high dose rate, HDR) is approaching or surpassing surgery as treatments for prostate cancer. Androgen deprivation therapy, external beam radiation therapy (conventional or IMRT), and high intensity focused ultrasound (HIFU) are also alternative prostate cancer treatments for.
Using the CyberKnife System to Treat Prostate Cancer
The CyberKnife® System is currently being used as monotherapy treatment for early stage prostate cancer or as a boost following conventional radiation therapy in place of IMRT or brachytherapy. The CyberKnife System can reproduce the conformality for organ coverage achievable with brachytherapy or IMRT and can track and compensate for organ motion during treatment delivery. Because of similar conformality and dose fractionation, local control and complication rates are expected to be similar to HDR brachytherapy. A low α/β ratio for prostate cancer indicates that a hypofractionated treatment regimen delivered via radiosurgery might be more effective than conventional external beam fractionation.
As a common and deadly form of cancer, extensive ongoing research is being conducted to develop effective new lung cancer treatments. Currently primary surgical resection of the lung tumor (lung cancer surgery) is the preferred treatment for early stage non-small cell lung carcinoma (NSCLC) for those patients that can tolerate surgery. For those patients who can not withstand lung cancer surgery (i.e., are medically inoperable), external beam radiotherapy (EBRT), stereotactic body radiotherapy (SBRT) and stereotactic radiosurgery (SRS) are alternative lung cancer treatments. Advanced stages of NSCLC are treated by surgery, SRS, SBRT, EBRT, chemotherapy, or a combination of these treatments depending on the extent of disease, the size of the lung tumor, and the presence of metastasis.
Using the CyberKnife System to Treat Lung Cancer:
Guidelines for CyberKnife® treatment were based on prior experiences with SBRT in the treatment of patients with medically inoperable NSCLC and those with NSCLC who refused surgery.
The CyberKnife System is unique in the world of SBRT thanks to its Synchrony® Respiratory Tracking System, which tracks and compensates for tumor movement during treatment delivery. This system was used in a study in which 23 patients received 15 Gy in a single session. There were no grade 3 or higher radiosurgery-related complications. The early tumor response was complete in 2 patients, partial in 15 and stable in 4, with two cases of progressive disease noted.
Spinal cancer surgery (surgical resection of the spinal tumor) and external beam radiotherapy are common spinal cancer treatments. More recently, however, radiosurgical treatment has proven to be a highly effective spinal cancer treatment.
Using the CyberKnife System to Treat Spine Lesions:
The CyberKnife® System treats lesions anywhere in the spine with high accuracy. Metastatic disease, and vascular malformations9 have been treated with the CyberKnife System at all levels of the spinal column. Recent published reports show high rates of tumor control significant, rapid, and durable pain relief,maintenance or improvement in mental and physical quality of life, and low rates of complications, comparable to that observed for intracranial radiosurgery treatments.
Although liver cancer surgery (surgical resection) is preferred among the treatments for liver cancer, only 20% of patients are candidates. Chemotherapy, chemoembolization, alcohol ablation, radiofrequency ablation, and cryoablation are alternative treatments for liver cancer. Recent studies have shown that stereotactic body radiation therapy may also be listed among effective liver cancer treatments.
Using the CyberKnife System to Treat Liver Cancer:
Thus far in the treatment of liver tumors, centers have treated with the CyberKnife® System alone or in combination with transhepatic arterial chemoembolization. Single-fraction approaches have achieved local liver tumor control with a dose of 25 Gy.4 Other centers have treated with three fractions to a total dose of 30-39 Gy, with just a few mild side effects noted. With the introduction of the Synchrony® Respiratory Tracking System, clinicians are better able to track liver tumors which move with respiration thus limiting dose to the liver tumor and minimizing dose to healthy adjacent liver tissue.
Relevant Liver Case Studies:
Primary Renal Cell Carcinoma
Pancreatic cancer surgery is the treatment of choice for early, resectable pancreatic cancer, but only 20% of tumors are resectable. Alternative pancreatic cancer treatments include external beam and intraoperative radiation therapy, which can decrease local progression in patients with locally advanced disease that is ineligible for pancreatic cancer surgery. Chemotherapy (typically with 5-fluorouracil (5-FU) or gemcitabine) has been used as an adjunct to radiation treatment.
Using the CyberKnife System to Treat Pancreatic Cancer:
Two published studies by Koong et al. have shown that the CyberKnife® System, equipped with the Synchrony® Respiratory Tracking System, was capable of delivering therapeutic radiation with minimal toxicity to tumors in patients with locally advanced pancreatic cancer. High rates of tumor control were obtained at the highest doses in these studies. Thus, CyberKnife radiosurgery may be considered among viable pancreatic cancer alternative treatments.
Relevant Pancreas Case Studies:
Renal cell carcinoma is treated with kidney cancer surgery (radical or partial nephrectomy, sometimes performed laparoscopically). Radiofrequency ablation, cryoablation, and arterial embolization are all kidney cancer treatments intended to selectively treat the kidney tumor and spare functional kidney tissue. Cytokine therapy (IL-2, IN-a) and chemotherapy have also been employed, and although response rates are low, selected patients do respond to these kidney cancer treatments.
Using the CyberKnife System to Treat Kidney Cancer:
Renal cell carcinomas are not very sensitive to small doses of radiation and normal kidney is extremely sensitive to radiation. High dose per fraction conformal stereotactic radiosurgery can achieve local control of small kidney tumors. The CyberKnife® System is able to deliver hypofractionation regimens which have been shown to effectively treat renal cell carcinoma metastases to the spine.
There are many other areas of the body that can be treated by the CyberKnife® System with extremely high accuracy.