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ACTH test after adenomectomy may accurately predict Cushing’s disease remission

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August 22, 2018

A plasma adrenocorticotropic hormone suppression test performed shortly after surgical adenomectomy may accurately predict both short- and long-term remission of Cushing’s disease, according to research published in Pituitary.

Cushing’s disease is caused by hypersecretion of adrenocorticotropic hormone (ACTH) by a pituitary adenoma, resulting in hypercortisolism,” Erik Uvelius, MD, of the department of clinical sciences, Skåne University Hospital, Lund University, Sweden, and colleagues wrote in the study background. “Surgical adenomectomy is the first line of treatment. Postoperative remission is reported in 43% to 95% of cases depending on factors such as adenoma size, finding of pituitary adenoma on preoperative MRI and surgeons’ experience. However, there is no consensus on what laboratory assays and biochemical thresholds should be used in determining or predicting remission over time.”

In the study, the researchers retrospectively gathered data from medical records of 28 patients who presented with Cushing’s disease to Skåne University Hospital between November 1998 and December 2011, undergoing 45 transsphenoidal adenomectomies.

On postoperative days 2 and 3, oral betamethasone was administered (1 mg at 8 a.m., 0.5 mg at 2 p.m., and 0.5 mg at 8 p.m.). Researchers assessed plasma cortisol and plasma ACTH before betamethasone administration and again at 24 and 48 hours, and measured 24-urinary free cortisol on postoperative day 3.

At 3 months postoperatively and then annually, plasma concentrations of morning cortisol and ACTH along with urinary-free cortisol and/or a low-dose dexamethasone suppression test were evaluated at the endocrinologists’ discretion. The researchers defined remission as lessening of clinical signs and symptoms of hypercortisolism, as well as laboratory confirmation through the various tests.

The researchers used Youden’s index to establish the cutoff with the highest sensitivity and specificity in predicting remission over the short term (3 months) and long term (5 years or more). Clinical accuracy of the different tests was illustrated through the area under curve.

The study population consisted of mainly women (71%), with a median age of 49.5 years. No significant disparities were seen in age, sex or surgical technique between patients who underwent a primary procedure and those who underwent reoperation. Two of the patients were diagnosed with pituitary carcinoma and 11 had a macroadenoma. ACTH positivity was identified in all adenomas and pathologists confirmed two cases of ACTH-producing carcinomas.

Of the 28 patients, 12 (43%) demonstrated long-term remission at last follow-up. Three patients were not deemed in remission after primary surgery but were not considered eligible for additional surgical intervention, whereas 13 patients underwent 17 reoperations to address remaining disease or recurrence. Four patients demonstrated long-term remission after a second or third procedure, equaling 16 patients (57%) achieving long-term remission, according to the researchers.

The researchers found that both short- and long-term remission were most effectively predicted through plasma cortisol after 24 and 48 hours with betamethasone. A short-term remission cutoff of 107 nmol/L was predicted with a sensitivity of 0.85, specificity of 0.94 and a positive predictive value of 0.96 and AUC of 0.92 (95% CI, 0.85-1). A long-term remission cutoff of 49 nmol/L was predicted with a sensitivity of 0.94, specificity of 0.93, positive predictive value of 0.88 and AUC of 0.98 (95% CI, 0.95-1). This cutoff was close to the suppression cutoff for the diagnosis of Cushing’s disease, 50 nmol/L. The cutoff of 25 nmol/L showed that the use of such a strict suppression cutoff would cause a low level of true positives and a higher occurrence of false negatives, according to the researchers.

“A 48 h 2 mg/day betamethasone suppression test day 2 and 3 after transsphenoidal surgery of Cushing’s disease could safely predict short- and long-term remission with high accuracy,” the researchers wrote. “Plasma cortisol after 24 hours of suppression showed the best accuracy in predicting 5 years’ remission. Until consensus on remission criteria, it is still the endocrinologists’ combined assessment that defines remission.” – by Jennifer Byrne

Disclosures: The authors report no relevant financial disclosures.