Feature | October 15, 2007

Armed and Dangerous Against Tumors

CyberKnife Centers of San Diego’s Donald Fuller, M.D., discusses fusion of radiosurgery with robotics

Donald Fuller, M.D., is a board certified radiation oncologist with CyberKnife Centers of San Diego Inc. Dr. Fuller earned his doctorate at the University of Washington School of Medicine in Seattle. He completed his internship at Santa Barbara (CA) Cottage Hospital and his radiation oncology residency at LDS Hospital in Salt Lake City. He is certified by the American Board of Radiology in Radiation Oncology.
Dr. Fuller joined Radiation Medical Group in 1988. His interests in the specialty include prostate cancer radiotherapy, prostate brachytherapy and radiation dose escalation for a variety of malignancies through the appropriate application of intensity modulated radiotherapy (IMRT), brachytherapy and SRS/SBRT techniques. He is one of the directors of Western Cancer Center and Radiation Medical Group, specializing in advanced technology integration.
What do you see as some of the advantages of using Accuray’s CyberKnife Robotic Radiosurgery System over more traditional radiation oncology technology, such as IMRT and IGRT?
FULLER: The primary advantage CyberKnife provides over other radiotherapy systems is the ability to accurately sharpen the radiation margin, significantly reducing exposure to nearby normal tissues. This is made possible by the unique CyberKnife image guided robotic target tracking methodology, which continuously updates the position of the tumor volume throughout treatment, keeping the radiation focus aligned within a millimeter or less, even if the tumor moves during the treatment. Target volume motion becomes a larger problem with shrinking radiation treatment margins, and the innovative CyberKnife target tracking methodology compensates for this problem far more effectively than other radiation delivery systems.
Respiratory gating, another tumor motion compensation technology used by some other radiation delivery systems, means synchronizing the beam with the breathing cycle, turning it on only during a specific phase of the breathing cycle. This approach also allows a narrowing of the radiation margin. Unfortunately, this approach is less efficient than the continuous target volume tacking method used by CyberKnife, and only applies to selected tumors in the chest and upper abdomen that are predictably correlated with breathing motion. By contrast, CyberKnife target volume tracking effectively compensates for all forms of tumor volume motion, not just breathing-induced tumor volume motion.
Non-gated IMRT/IGRT radiation delivery systems typically do not update the target volume position at all after treatment has started. To compensate, they require the inclusion of a larger margin, to envelop the entire possible range of tumor volume motion that may occur during treatment, exposing more normal tissue to radiation.
Another unique CyberKnife feature is its delivery of radiation dose from literally hundreds of different angles, giving a much more powerful ability to shape and conform the high radiation dose to the target volume. By comparison, other radiation delivery systems typically target through a much smaller number of fixed beams, comparatively reducing their capability to conform the high radiation dose so tightly to the tumor volume.
CyberKnife creates the delivery of precision directed three-dimensional ablative radiation dosing to a tumor volume, with minimal risk of serious injury to adjacent normal tissues, typically using one to five large radiation doses delivered in a week or less. Such large individual doses are not safely delivered with conventional radiation delivery systems, even those using IMRT or IGRT technology, due to the larger normal tissue radiation exposure associated with these approaches. As such, traditional radiation approaches, including IMRT and IGRT, are usually delivered using a dosing schedule that employs a much larger series of small radiation doses, typically extending over one to two months.
I should add that in some circumstances, such as a tumor that infiltrates or spreads with indiscreet margins, or to sterilize a potentially contaminated tumor surgical bed, a larger radiation treatment margin remains prudent, and in those circumstances, IMRT/IGRT or other forms of ‘conventional radiation’ remain the treatment of choice. CyberKnife will more often emerge as the treatment of choice when a narrower radiation coverage margin is more appropriate. Finally, in some cases, it may even be appropriate to combine both CyberKnife and non-CyberKnife forms of radiation in the same patient to further optimize the radiation coverage pattern to fit the tumor volume and spread pattern.
When radiation oncology technology equipped with adaptive radiotherapy software gains traction how do you foresee it competing with the CyberKnife?
Adaptive radiotherapy (ART) actually defines a different process than CyberKnife, so I do not see them directly competing. Adaptive radiotherapy means compensating for changes in tumor volume and patient body habitus that happen gradually over an entire course of radiotherapy, for example recalculating the target volume dosing to account for a tumor that is reduced by half, while a patient loses 15 pounds, over two months of radiotherapy, adjusting the treatment accordingly. In contrast, an entire CyberKnife course is given in one to five treatments in a week or less, which leaves it with a different charge. CyberKnife tracks and adjusts to changes in the target volume position during each individual treatment, updating its location 50-100 times or more per session, enabling surgical targeting precision, which unlocks short course ablative radiation dosing. So one (ART) is radiotherapy while the other (CyberKnife) is radiosurgery. There is a need for both techniques, depending upon the specific clinical situation.
There will be significant radiosurgical competition for CyberKnife though, as other radiation delivery systems develop their own target volume tracking methodology. Right now it would be my opinion that CyberKnife is far ahead of the pack in this regard, but with small armies of motivated device engineers, computer programmers and corporate backing, the future competitive landscape could change quickly. If CyberKnife has an Achilles Heel it would be the high cost of device procurement and operation and its relatively low patient throughput capability, such that a competitor who figured out a more efficient yet sufficiently robust radiosurgery solution would be particularly challenging. Of course, my interaction with Accuray suggests that they, too, are restlessly working to continuously upgrade the technical capabilities and operating efficiency of the CyberKnife, so competitors definitely have a high hurdle to clear. The CyberKnife product seems to evolve regularly to a more powerful product, reflecting the work of Accuray’s own impressive engineering and programming army.
What are some of the challenges you wrestled with in deciding to invest in a CyberKnife vs. traditional technology?
We consider the CyberKnife system to be ‘paradigm shifting’ radiation technology. That is why we purchased it. CyberKnife is the only system capable of delivering radiosurgical dosing precision throughout the body, and thus unlocks many new radiation applications. These will continue to grow as tumor imaging capability and computing power continue to grow, so CyberKnife is an investment in our future. It is the quintessential ‘next generation’ radiation delivery device.
The main caution I would supply to others contemplating the purchase of the CyberKnife system is that it is complex and expensive technology, with a limited patient throughput capability, which is really only suitable for ‘ablative’ radiosurgical-type dosing. It is primarily complementary rather than a replacement for other radiotherapy systems, and is best deployed in a practice that is large enough to support such an expensive, complicated and specialized application. Billing rules and insurance coverage may also be complex, so a potential CyberKnife purchaser also needs to be very aware of how their payer mix may react to the technology. One problem is that this technology is so new there is still a relatively small (although growing) literature base of support – a fact often used by insurers to deny coverage of the CyberKnife procedure.
What are some of the hard lessons you learned – good and bad – during the CyberKnife implementation process? And if you had to do it all over again, what would you change and why?
The most frustrating aspect of our CyberKnife experience has been the process of gaining insurance approval for the procedure in all cases where we recommend it. We have literally insurance plan medical directors attempt to look it up in a book and then deny coverage because ‘CyberKnife is not on the list.’ Though one would think that some basic explanation of the clinical and obvious radiation coverage advantage for the patient in question would correct such a problem, the process has often been amazingly bureaucratic. Even more amazingly, the insurers will often approve more expensive procedures such as major surgery or IMRT, because those applications are on ‘the list.’ So I think that at times, insurers are actually engaging in a form of ‘remote practice of medicine’ rather than insuring, and doing so from an inferior knowledge base – a practice that offends me greatly. And in many of these circumstances they are not even saving their own shareholders money.
In terms of the technology itself, there is a definite ‘learning curve’ as to what is or is not achievable with CyberKnife. In the ‘honeymoon stage’ one has a tendency to think this device can just about do anything, but with experience, as with all high technology devices, one learns that there are quirks, nuances and system limitations that need to be understood to most effectively and appropriately apply it.
How did you convince yourself that the clinical, financial and operational ROI for implementing CyberKnife meant it needed to be done now, as opposed to delaying it?
The first thing we did was research the clinical capabilities of the CyberKnife device and convinced ourselves that is was indeed a leap forward in radiation delivery methodology. We then calculated the likely utilization rate of CyberKnife in our practice, ran multiple detailed pro forma scenarios to ascertain the risk versus reward of purchase and operation, and surveyed the payer landscape before electing to proceed with purchase of the CyberKnife device.
What are some of the noteworthy clinical, financial and operational benefits you’ve derived from using the CyberKnife to date?
The major benefit has been the added ‘high technology’ aspect conferred to our practice through the early adoption of such a leading edge product. In the Internet era, patients increasingly seek this out, and so CyberKnife grows the practice in a way that would not otherwise happen. It has opened new clinical applications for us, allowing us to treat quite a number of conditions that were not previously referred for radiation treatment at all, such as tumors that have recurred in a prior field of radiation, or liver metastases, to name two examples. Financially, thus far, our pro forma expectations have been met, though a proliferation of multiple CyberKnife devices in close geographic proximity, or any substantial change in reimbursement by Medicare or other insurers could severely impact the financial benefit. There is definite and significant financial risk associated with this sort of investment. In our own case, we are also bolstered by a large existing ‘conventional’ radiotherapy practice that provides some added economic shielding in the event that CyberKnife economic performance ever falls below expectations.
For what indications are you using CyberKnife to treat now and what do you plan to add in the future? Why?
Interestingly, although CyberKnife was originally developed for neurosurgical applications, we are using it primarily outside the central nervous system, including prostate cancer, primary and secondary liver tumors, pancreatic and other abdominal cancers, metastatic melanomas, sarcomas (soft tissue tumors), selected lung cancers, head and neck cancers and lesions that have recurred after previous ‘conventional’ radiation therapy. In our own case we are already doing the ‘leading edge’ body applications and paradoxically, we could actually be a mirror image of many other CyberKnife practices, with traditional neurosurgical CyberKnife applications perhaps representing the single largest added future growth opportunity. Across the United States, it is interesting to note that different CyberKnife Centers have significantly different patient mixes, illustrating the flexibility of this technology to fill different niches in different communities.
Why does it make sense for a cancer treatment center to invest in and implement a CyberKnife – particularly if that facility is not attached to a hospital for financial support, including patient referrals?
Patient referrals do not come from hospitals. Patient referrals come from physicians, and as our society becomes ever more computer literate, patients more and more often refer themselves if they see a treatment that appears superior to a ‘traditional’ alternative. This phenomenon seems particularly prevalent in prostate cancer patients. If the patient referral base is there, then there is no specific reason that hospital participation is required. CyberKnife radiosurgery is a noninvasive outpatient procedure. A more valid reason for involving a hospital or hospital system is that hospital administrators are more used to making large financial investments of the magnitude required to procure and support a CyberKnife device. Ultimately, the situation in a given community will dictate whether this investment is best made by a hospital or a physician-based group. Some sort of financial strength is required to offset the risk of this investment.
If a radiation oncologist – or another cancer treatment center representative – came to you for advice on how to determine whether to invest in a CyberKnife or more traditional rad onc technology, what are five actionable tips would you give them to help them make the optimal choice?
1. Do you have a large enough patient base to support a tertiary device such as CyberKnife? If not, an ‘all in one’ device such as Varian Trilogy or Elekta Synergy that does IMRT/IGRT and limited radiosurgical applications probably makes more sense. CyberKnife is a dedicated radiosurgical device and so requires a larger base of support. Run pro forma with various patient loads and reimbursement assumptions to understand the reward versus risk of the investment.
2. Do you have the physics, imaging and information technology ‘horsepower’ to support this device? CyberKnife is probably the most technology intensive device of them all. If support in this regard seems doubtful for any reason, a practice should probably steer clear of CyberKnife in favor of a simpler, more traditional radiotherapy delivery device.
3. Is there support for CyberKnife in your community? Obviously, a quorum of skilled and motivated physician ‘proselytizers’ go a long way toward generating the necessary community support for such technology. On the other hand, if your referral base seems skeptical, and you are in a position of having to push hard to ‘sell it’ to them, you may be better off with ‘traditional’ radiotherapy delivery technology.
4. Are you an ‘early adopter’ or do you like 10-year prospective randomized study validation before adopting a new approach? One of these profiles fits the CyberKnife mold and the other shouldn’t touch it, because it will be quite awhile before there is a mature CyberKnife and body radiosurgery clinical literature base compared with ‘conventional’ treatment.
5. Examine your payor mix and economic situation. In general, ‘neurosurgical’ CyberKnife treatments seem to meet less insurance resistance than ‘body’ CyberKnife radiosurgical treatments, so a large ‘neurosurgical’ patient base may provide an easier reimbursement pathway, though this differential will likely erode as more CyberKnife/SBRT/radiosurgery data are published. Hospital-based versus free-standing billing rules and rates vary from region to region in the United States, so one needs to do their homework with the various payors to understand how to best structure the CyberKnife investment (Hospital-based versus free-standing) to assure the best chance of adequate reimbursement for such an expensive investment.
What are your top three priorities for the remainder of 2007 and for 2008 and why?
1. Our primary objective besides maximizing the CyberKnife operational effectiveness is to complete our IGRT (image-guided radiation therapy) upgrade process, as this is the next significant technological advance in ‘conventional’ radiotherapy. We are a comprehensive radiation oncology practice and it is very important to keep the entire practice at the leading edge, not just the CyberKnife practice.
2. Advanced diagnostic image processing (e.g., MRI, high-resolution CT, etc.) becomes more and more important as our radiation delivery technology advances. We need to recall that such elegant targeting methodology is of little use if one is not seeing the target volume accurately in the first place! The more ‘surgical’ we get with our radiation treatment margin, the more critical this aspect becomes.
3. Improved operating efficiency becomes more imperative as the investments and device complexity continue to grow.
How do you define what it means to be a state-of-the-art cancer treatment center?
Presently, our intent is to be a state-of-the-art radiation oncology/radiosurgery center. That is our core business. Beyond radiation though, our CyberKnife Center has been constructed using a collaborative, open staff model, particularly with regard to oncologic surgeons, who usually help us design the patient’s CyberKnife treatment, and also help define situations where a different approach such as classic surgical resection may be a better choice.
We essentially provide a ‘scaffolding’ or ‘backbone’ around which multiple physicians and surgeons may collaborate to create the best local treatment solution for each patient. Another major aspect of a cancer treatment center is medical oncology, the specialty in charge of the supervision and delivery of medical treatment for the cancer patient. We collaborate with medical oncologists throughout the entire region to optimally integrate systemic treatment (chemotherapy) with local therapy (surgery, radiation therapy, radiosurgery) for each patient. Finally, diagnostic radiology sophistication is critical.
In our community a dispersed model seems more effective than trying to collect all of the specialists under one roof, particularly noting that different health care delivery systems and different practices may adopt their own paradigm shifting approaches or devices at different times. We need to be nimble and remain able to select from the best aspects of an ever changing community ‘menu’ of support to stay at the ‘leading edge’ for our cancer patients.

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