To reduce their risk for prostate cancer men over 40 are encouraged to have

Answer;
To take an annual PSA test; 

To reduce their risk for prostrate cancer men over 40 are encouraged to have an annual PSA test.

Explanation; 
PSA test measures the level of PSA in a man's blood. Prostrate specific antigen is a protein by normal, as well as malignant, cells of the prostrate gland. The blood level of PSA is often elevated in men with prostrate cancer.