The lack of randomized, controlled trials (RCT) for interventional radiology (IR) is one of the major problems of IR, which has been discussed for many years (SIR Dotter—lecture 2008). The reasons for this are simple but difficult to overcome. IR does not control the patients, so they often do not control the trials. Second, performing a RCT is expensive and funding for device trials is very difficult, because there is still no regulatory need to produce RCT data for registration of a device. Finally, the IR market is small compared with, for example, interventional cardiology, and the industry is not willing to invest large sums, which are needed for a RCT. That is why we always see these small, underpowered, one-arm studies in IR, never reaching any level of evidence.
What does, "IR does not control the patients, so they often do not control the trials" mean? Patients are sent by primary doctors to IRs for one-time treatment, and then go back to the primary doctors for future care? In CCSVI, this is where we might see neurologist-controlled trials? Because the neurologists control us as MS patients...
The next two reasons have to do with funding. The device manufacturers don't need to fund a trial because there's no requirement that they do before the device gets approved for use. The IR market is small -- does 600,000 people with MS in the US change that or is that still small? -- and so the industry is not willing to invest large sums.
How did other researchers wanting to do interventional radiology randomized controlled trials overcome these obstacles? The link above discusses an ASTRAL trial about renal artery stenting. Where did their funding come from?