While I agree with Flipper, I do not agree that it is due to corruption. External devices are simply subject to much less regulation. I have some great massagers I that use electrical fields too. Supposedly FDA approved. Everyone gets the same treatment for similar devices.
They are simply allowed to make basic statistical claims once approved, even if they are projected and not actual. Since there was so little hope for patients, and the projections were statistically sound apparently, it was not necessary for them to have additional requirements spur upon such an external device.
Maybe at some point the FDA will reevaluate, but I don’t even think they can do that retroactively without some cause. Novocure will probably get to ride the DCVax wave.