INTRAOPERATIVE ADRENOCORTICOTROPIN LEVELS DURING TRANSSPHENOIDAL SURGERY FOR CUSHINGS-DISEASE DO NOT PREDICT CURE

Recently, intraoperative rapid immunochemiluminometric assay (ICMA) AC TH measurements have been used to evaluate the completeness of resecti on of ectopic ACTH-secreting tumors. This study evaluates whether this method can be applied to patients undergoing transsphenoidal surgery (TSS) for Cushing's disease to predict complete pituitary tumor resect ion. Eighteen patients with Gushing's disease undergoing TSS had plasm a ACTH concentrations measured by a standard ICMA every 10 min for 1 h immediately after pituitary tumor removal. Patients were evaluated po stoperatively for cure by standard criteria. ACTH levels were evaluate d for percentage decrease from baseline at each time point. Patients w ho were cured (n = 11) had statistically greater decreases in ACTH lev els (mean decrease 54%) than patients who were not (n = 7; 26% mean de crease, P < 0.04). By Receiver-Operator Characteristic (ROC) analysis, a reduction of at least 40% best predicted which patients were cured and which were not cured. This level of reduction was observed in 82% of cured patients, and a reduction of less than 40% was observed in 71 % of those not cured. The analysis misclassified 4 of the 18 patients, resulting in a diagnostic accuracy of 78%. Although the mean maximal decrease in ACTH concentrations after tumor removal was significantly different between cured and not cured patients with Gushing's disease, it was less dramatic than results in the previous ectopic ACTH study. This may relate to incomplete suppression and/or surgical manipulatio n of normal pituitary corticotrophs in patients with pituitary disease . In summary, in contrast to the ectopic ACTH syndrome, decline of pla sma ACTH during TSS does not accurately predict complete tumor resecti on.