<qa>  What is the primary efficacy variable?This is a prospective, randomized, stratified open-label Zometa hormonal ablation versus hormonal ablation alone multicenter clinical study evaluating the efficacy of Zometa 4mg given every 3 month as an adjunct to hormonal or surgical castration for prevention of bone metastases in locally advanced, high risk prostate cancer patients, who are hormone-naiv at time of randomization. the primary efficacy variable is the time to occurrence of first bone metastases. 