Glowing cancer tool illuminates benign, but dangerous, brain tumors during pituitary surgery

University of Pennsylvania School of Medicine

PHILADELPHIA – An experimental imaging tool that uses a targeted fluorescent dye successfully lit up the benign brain tumors of patients during removal surgery, allowing surgeons to identify tumor tissue, a new study from researchers at the Perelman School of Medicine at the University of Pennsylvania shows. The tumors, known as pituitary adenomas, are the third most common brain tumor, and very rarely turn cancerous, but can cause blindness, hormonal disorders, and in some cases, gigantism.

Findings from the pilot study of 15 patients, published this week in the Journal of Neurosurgery, build upon previous clinical studies showing intraoperative molecular imaging developed by researchers at Penn’s Center for Precision Surgery can improve tumor surgeries. According to first author John Y.K. Lee, MD, MSCE, an associate professor of Neurosurgery in the Perelman School of Medicine at the University of Pennsylvania and co-director of the Center for Precision Surgery, this study describes the first targeted, near infrared dye to be employed in brain tumor surgery. Other dyes are limited either by their fluorescent range being in the busy visible spectrum or by lack of specificity.

“This study heralds a new era in personalized tumor surgery. Surgeons are now able to see molecular characteristics of patient’s tumors; not just light absorption or reflectance,” Lee said. “In real time in the operating room, we are seeing the unique cell surface properties of the tumor and not just color. This is the start of a revolution.”

Non-specific dyes have been used to visualize and precisely cut out brain tumors during resection surgery, but this dye is believed to be the first targeted, near infrared dye to be used in neurosurgery. The fluorescent dye, known as OTL38, consists of two parts: vitamin B9 (a necessary ingredient for cell growth), and a near infrared glowing dye. As tumors try to grow and proliferate, they overexpress folate receptors. Pituitary tumors can overexpress folate receptors more than 20 times above the level of the normal pituitary gland in some cases. This dye binds to these receptors and thus allows us to identify tumors.

“Pituitary adenomas are rarely cancerous, but they can cause other serious problems for patients by pushing up against parts of their brain, which can lead to Cushing’s disease, gigantism, blindness and death,” Lee explained. “The study shows that this novel, targeted, near infrared fluorescent dye technique is safe, and we believe this technique will improve surgery.”

Lee says larger studies are warranted to further demonstrate its clinical effectiveness, especially in nonfunctioning pituitary adenomas.

A big challenge with this type of brain surgery is ensuring the entire tumor is removed. Parts of the tumor issue are often missed by conventional endoscopy approaches during removal, leading to a recurrence in 20 percent of patients. The researchers showed that the technique was safe and effective at illuminating the molecular features of the tumors in the subset of patients with nonfunctioning pituitary adenomas.

The technique uses near-infrared, or NIR, imaging and OTL38 fluoresces brightly when excited by NIR light. The VisionSense IridiumTM 4mm endoscope is a unique camera system which can be employed in the narrow confines of the nasal cavity to illuminate the pituitary adenoma. Both the dye and the camera system are needed in order to perform the surgery successfully.

The rate of gross-total resection (GTR) for the 15 patients, based on postoperative MRI, was 73 percent. The GTR with conventional approaches ranges from 50 to 70 percent. Residual tumor was identified on MRI only in patients with more severe tumors, including cavernous sinus invasion or a significant extrasellar tumor.

In addition, for the three patients with the highest overexpression of folate, the technique predicted post-operative MRI results with perfect concordance.

Some centers have resorted to implementing MRI in the operating room to maximize the extent of resection. However, bringing a massive MRI into the operating room theater remains expensive and has been shown to produce a high number of false-positives in pituitary adenoma surgery. The fluorescent dye imaging tool, Lee said, may serve as a replacement for MRIs in the operating room.

Co-authors on the study include M. Sean Grady, MD, chair of Neurosurgery at Penn, and Sunil Singhal, MD, an associate professor of Surgery, and co-director the Center for Precision Surgery.

Over the past four years, Singhal, Lee, and their colleagues have performed more than 400 surgeries using both nonspecific and targeted near infrared dyes. The breadth of tumor types include lung, brain, bladder and breast.

Most recently, in July, Penn researchers reported results from a lung cancer trial using the OTL38 dye. Surgeons were able to identify and remove a greater number of cancerous nodules from lung cancer patients with the dye using preoperative positron emission tomography, or PET, scans. Penn’s imaging tool identified 60 of the 66 previously known lung nodules, or 91 percent. In addition, doctors used the tool to identify nine additional nodules that were undetected by the PET scan or by traditional intraoperative monitoring.

Researchers at Penn are also exploring the effectiveness of additional contrast agents, some of which they expect to be available in the clinic within a few months.

“This is the beginning of a whole wave of new dyes coming out that may improve surgeries using the fluorescent dye technique,” Lee said. “And we’re leading the charge here at Penn.”

###

This study was supported in part by the National Institutes of Health (R01 CA193556), the Institute for Translational Medicine and Therapeutics of the Perelman School of Medicine at the University of Pennsylvania, and the National Center for Advancing Translational Sciences of the National Institutes of Health (UL1TR000003).

Editor’s Note: Dr. Singhal holds patent rights over the technologies presented in this article.

Penn Medicine is one of the world’s leading academic medical centers, dedicated to the related missions of medical education, biomedical research, and excellence in patient care. Penn Medicine consists of the Raymond and Ruth Perelman School of Medicine at the University of Pennsylvania (founded in 1765 as the nation’s first medical school) and the University of Pennsylvania Health System, which together form a $6.7 billion enterprise.

The Perelman School of Medicine has been ranked among the top five medical schools in the United States for the past 20 years, according to U.S. News & World Report’s survey of research-oriented medical schools. The School is consistently among the nation’s top recipients of funding from the National Institutes of Health, with $392 million awarded in the 2016 fiscal year.

The University of Pennsylvania Health System’s patient care facilities include: The Hospital of the University of Pennsylvania and Penn Presbyterian Medical Center — which are recognized as one of the nation’s top “Honor Roll” hospitals by U.S. News & World Report — Chester County Hospital; Lancaster General Health; Penn Wissahickon Hospice; and Pennsylvania Hospital — the nation’s first hospital, founded in 1751. Additional affiliated inpatient care facilities and services throughout the Philadelphia region include Good Shepherd Penn Partners, a partnership between Good Shepherd Rehabilitation Network and Penn Medicine.

Penn Medicine is committed to improving lives and health through a variety of community-based programs and activities. In fiscal year 2016, Penn Medicine provided $393 million to benefit our community.

Disclaimer: AAAS and EurekAlert! are not responsible for the accuracy of news releases posted to EurekAlert! by contributing institutions or for the use of any information through the EurekAlert system.

From https://eurekalert.org/pub_releases/2017-09/uops-gct090517.php

A retrospective analysis of postoperative hypokalemia in pituitary adenomas after transsphenoidal surgery

Abstract.

Background

Pituitary adenoma is one of the most common intracranial neoplasms, and its primary treatment is endoscopic endonasal transsphenoidal tumorectomy. Postoperative hypokalemia in these patients is a common complication, and is associated with morbidity and mortality. This study aimed to analyze the etiopathology of postoperative hypokalemia in pituitary adenomas after endoscopic transsphenoidal surgery.

Methods and Materials

This retrospective study included 181 pituitary adenomas confirmed by histopathology. Unconditional logistic regression analysis was used to calculate odds ratios (ORs) and 95% confidence intervals (CIs). Repeated measures ANOVA was used to analyze change in serum potassium levels at different time points.

Results

Multiple Logistic regression analysis revealed that only ACTH-pituitary adenoma (OR = 4.92, 95% CI [1.18–20.48], P = 0.029) had a significant association with postoperative hypokalemia. Moreover, the overall mean serum potassium concentration was significantly lower in the ACTH versus the non-ACTH group (3.34 mmol/L vs. 3.79 mmol/L, P = 0.001). Postoperative hypokalemia was predominantly found in patients with ACTH-pituitary adenoma (P = 0.033).

Conclusions

ACTH-pituitary adenomas may be an independent factor related postoperative hypokalemia in patients despite conventional potassium supplementation in the immediate postoperative period.

Cite this as

You L, Li W, Chen T, Tang D, You J, Zhang X. (2017) A retrospective analysis of postoperative hypokalemia in pituitary adenomas after transsphenoidal surgery. PeerJ5:e3337 https://doi.org/10.7717/peerj.3337

Read the entire article at https://peerj.com/articles/3337/

Comparison of MRI techniques for detecting microadenomas in Cushing’s disease

1Department of Neurological Surgery and 2Department of Radiology, University of Virginia Health Science Center, University of Virginia, Charlottesville, Virginia
ABBREVIATIONS ACTH = adrenocorticotropic hormone; CMRI = conventional MRI; DMRI = dynamic contrast-enhanced MRI; FSH = follicle-stimulating hormone; IPSS = inferior petrosal sinus sampling; SE = spin echo; SGE = spoiled-gradient echo 3D T1 sequence; SPGR = spoiled gradient–recalled acquisition; VIBE = volumetric interpolated breath-hold examination.

INCLUDE WHEN CITING Published online April 28, 2017; DOI: 10.3171/2017.3.JNS163122.

Correspondence Edward H. Oldfield, Department of Neurological Surgery, University of Virginia, Box 800212, Charlottesville, VA 22908. email: .
OBJECTIVE

Many centers use conventional and dynamic contrast-enhanced MRI (DMRI) sequences in patients with Cushing’s disease. The authors assessed the utility of the 3D volumetric interpolated breath-hold examination, a spoiled-gradient echo 3D T1 sequence (SGE) characterized by superior soft tissue contrast and improved resolution, compared with DMRI and conventional MRI (CMRI) for detecting microadenomas in patients with Cushing’s disease.

METHODS

This study was a blinded assessment of pituitary MRI in patients with proven Cushing’s disease. Fifty-seven patients who had undergone surgery for Cushing’s disease (10 male, 47 female; age range 13–69 years), whose surgical findings were considered to represent a microadenoma, and who had been examined with all 3 imaging techniques were included. Thus, selection emphasized patients with prior negative or equivocal MRI on referral. The MRI annotations were anonymized and 4 separate imaging sets were independently read by 3 blinded, experienced clinicians: a neuroradiologist and 2 pituitary surgeons.

RESULTS

Forty-eight surgical specimens contained an adenoma (46 ACTH-staining adenomas, 1 prolactinoma, and 1 nonfunctioning microadenoma). DMRI detected 5 adenomas that were not evident on CMRI, SGE detected 8 adenomas not evident on CMRI, including 3 that were not evident on DMRI. One adenoma was detected on DMRI that was not detected on SGE. McNemar’s test for efficacy between the different MRI sets for tumor detection showed that the addition of SGE to CMRI increased the number of tumors detected from 18 to 26 (p = 0.02) based on agreement of at least 2 of 3 readers.

CONCLUSIONS

SGE shows higher sensitivity than DMRI for detecting and localizing pituitary microadenomas, although rarely an adenoma is detected exclusively by DMRI. SGE should be part of the standard MRI protocol for patients with Cushing’s disease.

Full text at http://thejns.org/doi/full/10.3171/2017.3.JNS163122

Diagnosis and Differential Diagnosis of Cushing’s Syndrome

D. Lynn Loriaux, M.D., Ph.D.

N Engl J Med 2017; 376:1451-1459April 13, 2017DOI: 10.1056/NEJMra1505550

More than a century ago, Harvey Cushing introduced the term “pluriglandular syndrome” to describe a disorder characterized by rapid development of central obesity, arterial hypertension, proximal muscle weakness, diabetes mellitus, oligomenorrhea, hirsutism, thin skin, and ecchymoses.1 Cushing knew that this syndrome was associated with adrenal cancer,2 and he suspected that some cases might have a pituitary component.

On September 6, 1911, he performed a craniotomy on one of his patients (referred to as Case XLV) but found no pituitary tumor.3 In his description of the case, he goes on to say that “we may perchance be on the way toward the recognition of the consequences of hyperadrenalism.”2 With time, it became clear that the disorder could be caused by small basophilic adenomas of the pituitary gland,4 and the pluriglandular syndrome became known as Cushing’s syndrome.

Fuller Albright provided the next conceptual advance in an extraordinary report, published in the first volume of the Laurentian Hormone Conference, “The Effects of Hormones on Osteogenesis in Man”5:

It has been our concept that protoplasm in general, like the protoplasmic matrix of bone, is constantly being anabolized and catabolized at one and the same time; a factor which increases catabolism would lead to very much the same net result as a factor which inhibits anabolism, but there would be some differences; it is my belief that the “S” hormone [cortisol] is anti-anabolic rather than catabolic. . . . The anti-anabolism . . . is contrasted with the increased anabolism due to an excess of the “N” hormone [testosterone] in the adreno-genital syndrome. This anti-anabolism of protoplasm in Cushing’s syndrome accounts for not only the osteoporosis, but the muscular weakness, the thin skin, probably the easy bruisability, and possibly the atrophy of the lymphoid tissues and thymus.

Nonetheless, in the intervening years, the physical examination of patients suspected to have glucocorticoid excess focused on the anabolic changes, essentially to the exclusion of the antianabolic changes. With the rapid increase in the rate of obesity in the general population, Cushing’s syndrome can no longer be reliably separated from the metabolic syndrome of simple obesity on the basis of anabolic signs alone. However, the antianabolic changes in Cushing’s syndrome are very effective in making this distinction. This review focuses on the problems introduced into the diagnosis and differential diagnosis of Cushing’s syndrome by the obesity epidemic and on ways to alter the traditional approach, using the antianabolic changes of excess cortisol to separate patients with Cushing’s syndrome from obese patients with the insulin-resistant metabolic syndrome.

PHYSICAL EXAMINATION

Andreas Vesalius (1514–1564) published his transformational work on human anatomy, De Humani Corporis Fabrica Libri Septem, in 1543. It is the book that corrected many of Galen’s anatomical errors. The book was met with considerable hostility. As an example, Jacobus Sylvius (Jacques Dubois, 1478–1555), the world’s leading anatomist at the time and Vesalius’s former mentor, on being asked his opinion of the work, replied, “Galen is not wrong. It is man that has changed, and not for the better.”6 This was not true then, but it is true now.

Approximately one third of the U.S. population is obese. The worldwide prevalence of the metabolic syndrome among obese persons is conservatively estimated at 10%; that is, approximately 12 million people have the obesity-related metabolic syndrome.7,8 The clinical picture of this syndrome is almost the same as that of Cushing’s syndrome.9,10 The prevalence of undiagnosed Cushing’s syndrome is about 75 cases per 1 million population, or 24,000 affected persons. On the basis of these prevalence estimates, the chance that a person with obesity, hypertension, hirsutism, type 2 diabetes, and dyslipidemia has Cushing’s syndrome is about 1 in 500. In Harvey Cushing’s era, when obesity was rare, making the diagnosis of Cushing’s syndrome was the most certain aspect of the management of this disorder. Today, making the diagnosis is the least certain aspect in the care of patients with Cushing’s syndrome.

The metabolic syndrome caused by glucocorticoid hypersecretion can be differentiated from the obesity-associated metabolic syndrome with the use of a careful assessment of Albright’s antianabolic effects of cortisol. These effects — osteopenia, thin skin, and ecchymoses — are present in patients with Cushing’s syndrome but not in patients with simple obesity.

Patients in whom osteoporosis is diagnosed radiographically are more likely to have Cushing’s syndrome than those who do not have osteoporosis, with a positive likelihood ratio of 11.11-13 Today, a z score of −2 at the lumbar spine supports this criterion. Skinfold thickness is conveniently measured with an electrocardiographic caliper that has the points dulled with a sharpening stone and the screws tightened so that the gap is maintained when the caliper is removed from the skinfold. The skin over the proximal phalanx of the middle finger of the nondominant hand is commonly used for this measurement

 

(Figure 1 FIGURE 1Measurement of Skinfold Thickness.). A thickness of less than 2 mm is considered to be thin skin. Patients who have thin skin are more likely to have Cushing’s syndrome, with a positive likelihood ratio of 116

 

(Figure 2 FIGURE 2 Comparison of Skinfold Thickness in Patients with Cushing’s Syndrome and Those with Other Conditions Related to Insulin Resistance.).13-15 Finally, patients who have three or more ecchymoses that are larger than 1 cm in diameter and not associated with trauma such as venipuncture are more likely to have Cushing’s syndrome than are patients without such findings, with a positive likelihood ratio of 4.13,16

If we know the prevalence of undiagnosed Cushing’s syndrome in the population of persons with the obesity-related metabolic syndrome, we can begin to calculate the probability that a person has Cushing’s syndrome, using the likelihood ratios for the antianabolic features observed on physical examination. Likelihood ratios can be converted into probabilities with the use of Bayes’ theorem. This conversion is markedly facilitated by the Fagan nomogram for this purpose.17

The prevalence of undiagnosed Cushing’s syndrome is not known, but it can be estimated. Two persons per 1 million population die from adrenal cancer every year.18 The current life span for patients with adrenocortical carcinoma, after diagnosis, is between 2 and 4 years.19,20 Allowing 3 years to make the diagnosis, the prevalence of undiagnosed Cushing’s syndrome is 6 cases per million. In most case series of Cushing’s syndrome, an average of 8% of patients have adrenal carcinoma.21 If 6 per million is 8% of the group, the total Cushing’s syndrome group is 75 persons per million, or 24,000 persons. If all 24,000 patients are included in the metabolic syndrome group, comprising 12 million people, the prevalence of Cushing’s syndrome is 0.002, or 0.2%. With a probability of 0.2% and a likelihood ratio of 116 for thin skin, 18 for osteopenia, and 4 for ecchymoses, the probability that a patient with these three findings has Cushing’s syndrome is 95%.

URINARY FREE CORTISOL

The diagnosis of all endocrine diseases requires a clinical presentation that is compatible with the disease, as well as identification of the pathophysiological cause. An assessment for excess glucocorticoid effects can be made by measuring the 24-hour urinary free cortisol level.22 There are two kinds of free cortisol: plasma protein-unbound cortisol and cortisol unconjugated to sulfuric or hyaluronic acid. Protein-unbound cortisol is filtered in the glomerulus and then reabsorbed in the collecting system. About 3% of filtered cortisol ends up in the urine. This free cortisol in the urine is unconjugated. Thus, the urinary free cortisol level is a direct reflection of the free, bioactive cortisol level in plasma. The free cortisol level is quantified in a 24-hour urine sample by averaging the increased secretion of cortisol in the morning and the decreased secretion in the afternoon and at night. Urinary creatinine is also measured to determine whether the collection is complete. Creatinine levels of less than 1.5 g per day for men and less than 1 g per day for women indicate incomplete collection, and the test should be repeated in patients with these levels.

Unconjugated cortisol can be extracted directly from urine with a nonpolar lipid solvent. After extraction, the cortisol is purified by means of high-pressure liquid chromatography and then quantified with a binding assay, usually radioimmunoassay. Free cortisol also can be quantitated directly by means of mass spectroscopy. The urinary free cortisol assay of choice uses high-pressure liquid chromatographic separation followed by mass spectrometric quantitation.23 With the use of this assay, the urinary free cortisol level in healthy adults ranges from 8 to 51 μg per 24 hours (mean [±SD], 23±8). Clinical depression increases urinary free cortisol excretion, and most studies show that the level of urinary free cortisol ranges from 10 to 60 μg per day in patients with typical clinical signs and symptoms of depression. If we use 60 μg per day as the cutoff between normal values (<60 μg per day) and elevated values (≥60 μg per day), urinary free cortisol excretion of 62 μg per day or more has a positive likelihood ratio of 11.24 Thus, in a patient presenting with obesity, hypertension, type 2 diabetes, and hirsutism who has thin skin, osteopenia, ecchymoses, and an elevated urinary free cortisol level, the probability of Cushing’s syndrome is 1 (100%). For such patients, the clinician should move directly to a differential diagnostic evaluation.

DEXAMETHASONE-SUPPRESSION TEST

The dexamethasone-suppression test is commonly used in the diagnosis of Cushing’s syndrome. This test was developed by Grant Liddle in the early 1960s as a differential diagnostic test to separate corticotropin-dependent from corticotropin-independent Cushing’s syndrome. This is now done by measuring the plasma corticotropin level. Unfortunately, dexamethasone suppression has continued to be used as a screening test for Cushing’s syndrome.

The control group for this test comprises patients with obesity and depression in whom cortisol secretion is not suppressed in response to an oral dose of 1 mg of dexamethasone at midnight. Of the current U.S. population of 360 million people, approximately one third (120 million people) are obese. Of those who are obese, 10% (12 million people) have depression. In half these patients (6 million people), the plasma cortisol level will not be suppressed in response to a dexamethasone challenge. On the basis of my estimate of the current prevalence of undiagnosed Cushing’s syndrome (24,000 cases) and the estimate of the at-risk population (6 million persons), the positive predictive value of the dexamethasone-suppression test is only 0.4%. Thus, this test should not influence what the physician does next and should no longer be used for this purpose.

OUTLIERS

For patients with convincing evidence of Cushing’s syndrome on physical examination and an elevated 24-hour urinary free cortisol level, the differential diagnostic process outlined below should be initiated. However, a small group of patients will not meet these criteria.

Some patients have a strongly positive physical examination but low or zero urinary free cortisol excretion. Plasma corticotropin levels are suppressed in these patients. These patients are receiving exogenous glucocorticoids. The glucocorticoid must be identified, and a plan must be made for its discontinuation. Sometimes the glucocorticoid is being given by proxy (e.g., by a parent to a child), and no history of glucocorticoid administration can be found. Nevertheless, the glucocorticoid must be identified and discontinued.

Other patients have few or no clinical signs of Cushing’s syndrome but do have elevated urinary free cortisol excretion. Plasma corticotropin is measurable in these patients. They are usually identified during an evaluation for arterial hypertension. All such patients should undergo inferior petrosal sinus sampling to determine the source of corticotropin secretion. Ectopic sources are almost always neoplastic and are usually in the chest.25 Patients with eutopic secretion usually have the syndrome of generalized glucocorticoid resistance.26

Finally, a few patients have convincing findings on physical examination coupled with a normal urinary free cortisol level. In such cases, the clinician should make sure that urinary free cortisol is being measured with high-performance liquid chromatography and mass spectrometry, that renal function is normal, and that the collections are complete. “Periodic” Cushing’s syndrome must be ruled out by measuring urinary free cortisol frequently over the course of a month.27 If these efforts fail, the patient should be followed for a year, with urinary free cortisol measurements performed frequently. No additional tests should be performed until the situation is sorted out. More tests would be likely to lead to an unnecessary surgical procedure.

DIFFERENTIAL DIAGNOSIS

The differential diagnosis of Cushing’s syndrome is shown in Figure 3

FIGURE 3Differential Diagnosis of Cushing’s Syndrome.. If plasma corticotropin is measurable, the disease process is corticotropin-dependent. If corticotropin is not measurable, the process is corticotropin-independent.

Corticotropin-dependent causes of Cushing’s syndrome are divided into those in which the corticotropin comes from the pituitary (eutopic causes) and those in which the corticotropin comes from elsewhere (ectopic causes). This differentiation is made with the measurement of corticotropin in inferior petrosal sinus plasma and the simultaneous measurement of corticotropin in peripheral (antecubital) plasma immediately after corticotropin-releasing hormone stimulation of pituitary corticotropin secretion. In samples obtained 4, 6, and 15 minutes after stimulation with corticotropin-releasing hormone, eutopic corticotropin secretion is associated with a ratio of the central-plasma corticotropin level to the peripheral-plasma corticotropin level of 3 or more. Ectopic corticotropin secretion is associated with a central-to-peripheral corticotropin ratio of less than 3. The positive predictive value of this test is 1 (Figure 4

FIGURE 4Maximal Ratio of Corticotropin in Inferior Petrosal Sinus Plasma to Corticotropin in Peripheral Plasma in Patients with Cushing’s Syndrome, Ectopic Corticotropin Secretion, or Adrenal Disease.).28

Although some authorities suggest that inferior petrosal sinus sampling can safely be bypassed in patients with corticotropin-dependent Cushing’s syndrome and a well-defined pituitary adenoma, I disagree. The incidence of nonfunctioning pituitary microadenomas is between 15% and 40%.29 This means that up to 40% of patients with ectopic secretion of corticotropin have an incidental pituitary abnormality. If it is assumed that the pituitary abnormality is responsible for corticotropin secretion, 15 to 40% of patients with ectopic secretion of corticotropin will be misdiagnosed and submitted to a transsphenoidal exploration of the sella turcica and pituitary gland. The prevalence of ectopic corticotropin secretion in the population of patients with undiagnosed Cushing’s syndrome is about 10%, accounting for 2400 patients. Up to 40% of these patients, or 960, have an incidental pituitary tumor. The mortality associated with transsphenoidal microadenomectomy is 1%.30 If all 360 to 960 patients undergo this procedure, there will be up to 10 deaths from an operation that can have no benefit. For this reason alone, all patients with corticotropin-dependent Cushing’s syndrome should undergo inferior petrosal sinus sampling to confirm the source of corticotropin secretion before any surgical intervention is contemplated.

Patients with eutopic corticotropin secretion are almost certain to have a corticotropin-secreting pituitary microadenoma. An occasional patient will have alcohol-induced pseudo–Cushing’s syndrome. The slightest suggestion of alcoholism should lead to a 3-week abstinence period before any surgery is considered.31

Patients with ectopic corticotropin secretion are first evaluated with computed tomography (CT) or magnetic resonance imaging (MRI) of the chest. In two thirds of these patients, a tumor will be found.25 If nothing is found in the chest, MRI of the abdominal and pelvic organs is performed. If these additional imaging studies are also negative, there are two options: bilateral adrenalectomy or blockade of cortisol synthesis. If blockade is chosen, the patient should undergo repeat scanning at 6-month intervals.32 If no source is found by the end of the second year, it is unlikely that the source will ever be found, and bilateral adrenalectomy should be performed for definitive treatment (Doppman JL: personal communication).

Corticotropin-independent Cushing’s syndrome is usually caused by an adrenal neoplasm. Benign tumors tend to be small (<5 cm in diameter) and secrete a single hormone, cortisol. The contralateral adrenal gland is suppressed by the cortisol secreted from the tumorous gland. If the value for Hounsfield units is less than 10 and the washout of contrast material is greater than 60% at 15 minutes, the tumor is almost certainly benign.33 Such tumors can be treated successfully with laparoscopic adrenalectomy.

The syndromes of micronodular and macronodular adrenal dysplasia usually affect both adrenal glands. The nodules secrete cortisol. Corticotropin is suppressed, as is the internodular tissue of the adrenal glands. Percutaneous bilateral adrenalectomy, followed by glucocorticoid and mineralocorticoid treatment, is curative.

Adrenal tumors secreting more than one hormone (i.e., cortisol and androgen or estrogen) are almost always malignant. Surgical removal of all detectable disease is indicated, as is a careful search for metastases. If metastases are found, they should be removed. This usually requires an open adrenalectomy. It goes without saying that adrenal tumors, nodules, and metastases should be treated by the most experienced endocrine cancer surgeon available.

If the plasma cortisol level on the morning after a transsphenoidal microadenomectomy is 0, the operation was a success. The patient should be treated with oral hydrocortisone, at a dose of 12 mg per square meter of body-surface area once a day in the morning, and a tetracosactide (Cortrosyn) stimulation test should be performed at 3-month intervals. When the tetracosactide-stimulated plasma cortisol level is higher than 20 μg per deciliter (551 μmol per liter), cortisol administration can be stopped. The same rule applies in the case of a unilateral adrenalectomy. If the adrenalectomy is bilateral, cortisol, at a dose of 12 to 15 mg per square meter per day, and fludrocortisone (Florinef), at a dose of 100 μg per day, should be prescribed as lifelong therapy.

SUMMARY

The obesity epidemic has led to necessary changes in the evaluation and treatment of patients with Cushing’s syndrome. The most dramatic change is the emphasis on the antianabolic alterations in Cushing’s syndrome, which can provide a strong basis for separating patients with Cushing’s syndrome from the more numerous patients with obesity and the metabolic syndrome. More can be done along these lines. Likelihood ratios are known for proximal muscle weakness and can be known for brain atrophy and growth failure in children.

The dexamethasone-suppression test, although still very popular, no longer has a role in the evaluation and treatment of patients with Cushing’s syndrome. Only three biochemical tests are needed: urinary free cortisol, plasma corticotropin, and plasma cortisol measurements. Urinary free cortisol excretion is the test that confirms the clinical diagnosis of Cushing’s syndrome. To be trustworthy, it must be performed in the most stringent way, with the use of high-pressure liquid chromatography followed by mass spectrometric quantitation of cortisol. Measurement of plasma corticotropin is used to separate corticotropin-dependent from corticotropin-independent causes of Cushing’s syndrome and to separate eutopic from ectopic secretion of corticotropin. Inferior petrosal sinus sampling should be performed in all patients with corticotropin-dependent Cushing’s syndrome because of the high prevalence of nonfunctioning incidental pituitary adenomas among such patients. Measurement of plasma cortisol has only one use: determining the success or failure of transsphenoidal microadenomectomy or adrenalectomy. If the plasma cortisol level is not measurable on the morning after the operation (<5 μg per deciliter [138 μmol per liter]), the procedure was a success; if it is measurable, the operation failed. The surgeon must not administer intraoperative or postoperative synthetic glucocorticoids until the plasma cortisol level has been measured.

Successful evaluation of a patient who is suspected of having Cushing’s syndrome requires an endocrinologist who is skilled in physical diagnosis. Also required is a laboratory that measures urinary free cortisol using high-performance liquid chromatography and mass spectrometry and that can measure plasma cortisol and plasma corticotropin by means of radioimmunoassay.

Inferior petrosal sinus sampling is performed by an interventional radiologist. The treatment for all causes of Cushing’s syndrome, other than exogenous glucocorticoids, is surgical, and neurosurgeons, endocrine surgeons, and cancer surgeons are needed. This level of multidisciplinary medical expertise is usually found only at academic medical centers. Thus, most, if not all, patients with Cushing’s syndrome should be referred to such a center for treatment.

Disclosure forms provided by the author are available with the full text of this article at NEJM.org.

No potential conflict of interest relevant to this article was reported.

SOURCE INFORMATION

From the Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health and Science University, Portland.

Address reprint requests to Dr. Loriaux at the Division of Endocrinology, Diabetes, and Clinical Nutrition, Oregon Health and Science University, 3181 SW Sam Jackson Park Rd., L607, Portland, OR 97239-3098, or at .

From http://www.nejm.org/doi/full/10.1056/NEJMra1505550

Endoscopic Surgery on a Pituitary Adenoma

Philip Theodosopoulos, M.D. is Professor and Vice-Chair of Neurological Surgery at the University of California, San Francisco. He is the Director of the Skull Base Tumor Program and has extensive experience performing endoscopic transsphenoidal pituitary surgery for pituitary tumors (over 1000 operations) and other disease processes as well as tumors of the base of the skull.

In this video Dr. Theodosopoulos illustrates portions of an endoscopic resection of a pituitary adenoma.

 

To learn more about Dr. Theodosopoulos and to schedule an appointment for consultation please copy this link:
neurosurgery.UCSF.edu/index.php/about_us_faculty_theodosopoulos.html

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