Tracking with CK may be cool, but it can be done with LINAC-based SBRT approaches too. You don't necessarily need Calypso for that.
Brainlab for example does offer a KV-based real-time solution for this on their Novalis system.
We use this. It doesn't "track" and adjust the plan, but rather if there is patient motion, the treatment is interrupted. The reality is that significant motion is rarely an issue even with frameless SRS in adults, but it's good to have a realtime system monitoring as a failsafe. The gamma knife shops swear to me that they would only treat single fraction SRS with a rigid head frame, but that of course sounds barbaric to me now seeing our current system and results.
I am not persuaded that the dose distribution with cyber knife is better than with modern dynamic IMRT, especially if you are using some of the newer thinner MLCs like the Elekta-Agility for example.
I'd love to actually see the plans compared. My suspicion is the conformality indices would be quite similar, and whatever difference is probably not of clinical relevance.
does the linac "move" several times a minute to respond to patient/tumor motion?
Our arc plans for prostate take about 1-2 minutes to deliver. We align to plain gold seed fiducials and start the arc immediately. With PTV margin, intrafraction motion is practically irrelevant on this time scale. We do a lot of SBRT liver treatment in the same fashion. With ITV/PTV, typically the liver can be safely treated accounting for respiratory motion, and typically much faster than with CyberKnife. However, if there is too much respiratory motion or the tumor is too big to treat with an ITV, you still don't need a CyberKnife. Just respiratory gate it with a respiratory tracking system. The treatment time still comes out fairly similar to a CK.
Back to the original post, does it matter if the patient have NSCLC vs. Small Cell LC assuming both are early stage without mediastinum involvement?
Neither of these scenarios are appropriate for SBRT (assuming that the early NSCLC is compressing a major bronchus). This thread is raising my eyebrows for two reasons.
1) SDN forbids personal medical advice to begin with. Due to liability, we are not supposed to be providing any medical advice on this site.
2) You have provided so little of the details of the case, that it's hard to know what the most appropriate modality is for the care of this patient. The patient needs a formal consultation. If the patient wants to travel and have a formal consultation, have them pick a major center (i.e. a NCI designated cancer center) based on whatever measures are most convenient such as distance and just go there. The expertise of a lung specialist radiation oncologist (available at any major cancer center in the USA) far outweighs whatever benefits of whatever technology they have available at their site. i.e. Having the best hammer does not make you the best carpenter. Further, if this patient has compression of a major bronchus due to lung cancer, they may need treatment sooner rather than later, which means deliberation on where to be treated should be short. Your patient likely needs consultation and radiation treatment with haste, not after detailed discussion of radiation technology.