No we can't use this radio signals to see tumors, because science is not magic and wishful thinking will not solve the technical problems. Let's try to name a few:
The radio signals are absorbed by wet salty meatbags, so you can find them using radio signals, but you can't see thru them. If you raise the power to compensate the absorption, you will cook the meatbags, like a microwave oven.
If you were lucky to get a signal at the other end, the radio signal can distinguish between meat-bone-air-water, but not between tissues like meat and tumors that have a somewhat similar composition. A tomography use contrast to try to distinguish them. A magnetic resonance is better, but it use a huge magnet (and in some cases it use contrast too).
And also, the radio frequency that they are using has a wavelength of an inch approximately. So roughly it can resolve things that are an inch long, so it must be a big tumor to be visible. Perhaps you can try with a higher frequency that has a smaller wavelength.
And if I understand correctly, this device needs a lot of calibration, so you need version of the part of the body without the tumor and a version with tumors of different sizes and positions to calibrate the device and then try to use it in the real subject.