I am not a fan of using the word "fuel" as a characterization of the relationship between prostate cancer and testosterone. It is too outdated, and misses too much of what now know. Testosterone is not consumed in the process, does not provide the energy for growth, and is not necessary at all for growth, as in the ARv7 variant.
The AR is a transcription factor. That is the new (for me) starting point for comprehension.