I am not a doctor nor an expert in this area, but I would presume that would be a valid risk if the frequency were not tuned specifically to resonate the tumor

I am not a doctor nor an expert in this area, but I would presume that would be a valid risk if the frequency were not tuned specifically to resonate the tumor prior to increasing the amplitude. And then there is the matter of focus / accuracy. Perhaps nih.gov has a study with numbers to show the attainable accuracy and what statistics are given back to the equipment and the doctor to compensate and tune the signal. My understanding is that the inverse is generally true, in that, there is too much heat and the surrounding area is scarred.