BACKGROUND - Several investigators have recommended serial measurements of serum cortisol in the days following pituitary surgery to identify patients at risk of recurrence.
OBJECTIVE - We systematically reviewed the literature on this topic and analyzed the usefulness of this test in our own patient population.
METHODS - We identified studies publishing data regarding recurrence rates after transsphenoidal surgery for Cushing's disease, focusing on studies with data regarding patients with early postoperative cortisol levels. We determined a cumulative relative risk of having a subnormal vs normal cortisol level postoperatively using a fixed-effects meta-analysis model. Additionally, we analyzed our own patients with Cushing's disease undergoing transsphenoidal surgery and performed Kaplan-Meier analysis of recurrence-free survival for patients with undetectable, subnormal but detectable, and normal immediate 8 AM serum cortisol levels.
RESULTS - Fourteen studies met inclusion criteria. The length of follow-up varied between 32 and 115 months. The cumulative rate of recurrence in the group of patients with subnormal cortisol levels was 9% (95% confidence interval: 6%-12%). The cumulative rate of recurrence in the group with normal cortisol levels was 24% (95% confidence interval: 17%-31%). We analyzed 73 of our own patients and found similar recurrence rates in patients with subnormal vs normal early postoperative cortisol levels (4% vs 22%, chi2 test, P < .05).
CONCLUSION - Although a subnormal early postoperative cortisol level is predictive of improved outcome after transsphenoidal surgery for Cushing's disease, it is not analogous with cure, nor is a normal level completely predictive of future failure.