Like most things I think you can make veganism work if you do it sensibly, although why exactly you'd want to I have no fucking idea.
From what I can remember David Haye did something like 15 months of veganism through his latter stint as a cruiserweight to help keep the weight off.
Even with the removal of a testicle, chemo or radiation therapy is usually recommended, which is why I credit the Hoxey treatment with aiding in my remission. My Dr. recommended the Hoxey treatment because my metabolism is so high that the nausea associated with chemotherapy would have probably starved me to death. As it is, I am 40 years old, eat approx. 3500 to 4000 calories a day and STILL maintain my weight of 140 lbs. In fact if I don't eat like that I tend to lose weight.
I wouldn't have guessed that the one-testicled homeopathy guy was the anti-vegan in this thread.