If a dude has cancer in his testicle will he end up with high pitched voice?

No...but if the dude: Were to lose both testicles for any reason he might maintain a "boy soprano" voice, eunuchs were exactly this. A man with one testicle with cancer and it is removed, stil has another, and if his voice has or had not changed, the other testis makes suffiicent testosterone to provide male characteristics, and if the testosterone level is low, it can be replaced. Still a real dude.

No: The change in the pitch of the voice occurs at puberty when the larynx enlarges. Once the larynx has reached its adult size, even removing the testes will not change the pitch.