I was 29 when I had radiosurgery. Not Gamma Knife, but close enough for government work. From the studies I've read, the success rate of the GK is upwards of 90%.
You may or may not have problems as a result of the procedure. Radiation is a tricky thing; it's a Godsend in some ways, but it's a curse in others. It's not a very good answer, but it "just depends." It depends on the location of the tumor. It depends on the skill of the GK operator. It depends on you as a patient. It depends on pure blind luck. Like most other medical procedures, nobody really knows how it's going to turn out, but, all other things being equal, the GK is probably going to give you as high of a chance for success as any other option.
Just remember, at this age, you're (I assume) relatively healthy and able to deal with and recover from any effects of the radiation. That ability will only diminish as you age. Also, that tumor is already starting to get up there in size, and it probably has a long time to grow if you're only 32.
Best of luck!
