Five genetic variants associated with prostate cancer.

n engl j med 358;25 www.nejm.org june 19, 2008 2738 less than originally planned. Landry and Oliver propose a three-group trial (norepinephrine alone, vasopressin alone, and the two combined), which raises two concerns. First, the sample-size requirements for three-group trials are onerous — much greater than those for two-group trials. Second, treating patients with vasopressin alone would be difficult because norepinephrine is used routinely as the standard of care.5 Mogyorosi asks about the rate of hyponatremia in VASST. Hyponatremia was recorded only if it was considered to be a serious adverse event, so the rate reported (0.3%) does not represent all cases of hyponatremia. Nonetheless, we found it reassuring that severe hyponatremia in the vasopressin group was extremely rare and was not more frequent than in the norepinephrine group. We did not use an algorithm for hyponatremia; fluid and electrolyte levels were managed by clinical teams at each center. James A. Russell, M.D. Keith R. Walley, M.D.