European Journal of
Nuclear Medicine C by Springer-Verlag 1979
Adrenal Scintigraphy With 1311-19-Iodocholesterol in the Diagnosis of Cushing’s Syndrome Associated With Adrenal Tumor
G. B. Barliev
Medical Academy, Institute of Endocrinology and Gerontology, Radioisotope Laboratory, Christo Michailov 6, Sofia, Bulgaria
Abstract. Seven patients with Cushing’s syndrome sec- ondary to adrenocortical tumors were studied using 1311-19-iodocholesterol. The diagnosis of all cases were verified histologically. In three cases with ade- noma the uptake of the tracer was in the tumor only, while the two patients with adrenocortical carcinoma failed to show adrenal accumulation of the labelled compound.
In two patients there was a hyperplasia-like scin- tigraphic pattern, while the stimulation and suppres- sion biochemical tests suggested adrenal tumor. One of these cases was verified as a mixed form (adenoma plus hyperplasia), and the tumor bearing gland was significantly larger on the scan which helped the preo- perative localization. In the other case, verified as bilateral multiple adrenocortical adenomas, the auto- nomus function of both adrenals was proved by dexamethasone suppression scanning. It seens reason- able to use the latter as an adjunctive diagnostic procedure in patients where there is a discrepancy between the standart scintiscan and the biochemical indexes of adrenal hyperfunction.
Introduction
The diagnostic value of adrenal scintigraphy with 131I-19-iodocholesterol has been proved in patients with Cushing’s syndrome secondary to adrenocorti- cotropic hormone excess (Anderson and Beierwaltes, 1974; Beierwaltes et al., 1971; Moses et al., 1974), adrenocortical adenoma and carcinoma (Anderson and Beierwaltes, 1974; Jorgensen et al., 1975; Moses et al., 1974; Troncone et al., 1977), and postsurgical adrenal remnants (Schteingart et al., 1972).
In this article our experience in the scintigraphic evaluation of patients with Cushing’s syndrome sec- ondary to adrenocortical neoplasms is summarized.
Material and Methods
Seven patients were examined after intravenous administration of 1 mCi per 50 kg of body weight of 1311-19-iodocholesterol produced by CEA-SORIN. The radiopharmaceutical is a sterile non-pyrogenic solution of 1311-19-iodocholesterol in an aqueous solution of 0.9% sodium chloride 10% ethanol and 1% tween 80. To suppress the accumulation of radioactivity in the thyroid, Lugol’s solution was given as 5 drops twice daily, for 10 days start- ing on the day of injection.
The scans were produced between the 6th and the 9th day after injection with Picker Magnascanner 500i, provided with a 12,5 cm focus and 55 hole high energy collimator. The scanning speed was 20-40 cm min-1. All scans were taken posteriorly, so that the left adrenal is seen on the left side of each scintigram. The 12th thoracic vertebra was located on the back of the patients and transferred to the dot paper scan.
In one patient, three months after the standard scintiscan, a suppression test was performed by giving dexamethasone, 4 mg orally daily, beginning two days before the radiocholesterol injec- tion and continuing until the adrenal scans were completed. In another patient the scanning was repeated 6 months after the remo- val of adenoma.
The diagnosis of all cases was verified histologically. The group included three patients with adrenocortical adenoma, one patient with a mixed form (adenoma plus hyperplasia), one patient with bilateral multiple adenomas and two patients with carcinoma.
Results
All three patients with adenoma showed uptake of the tracer in the tumor only. In one of these patients the normal adrenocortical tissue was visualized 6 months after removal of the neoplasm (Fig. 1).
The patient with the mixed form showed bilateral visualization of the adrenal glands on the scan, the tumor bearing gland being relatively larger (Fig. 2). The scintigraphic image was interpreted as “bilateral asymmetrical hyperplasia”, but there was no response to either ACTH-stimulation or dexamethasone sup- pression, so that the most reasonable preoperative diagnosis appeared to be adrenocortical tumor. At
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operation an adenoma was found in the right adrenal. The histological examination revealed an adenoma developing in a hyperplastic gland.
The scintigraphic images of the patient with multi- ple bilateral adenomas are presented in Fig. 3. The standard scintiscan showed “bilateral hyperplasia”, but the stimulation and suppression biochemical tests suggested adrenocortical tumor. Dexamethasone sup- pression scanning showed that both adrenals intensely absorbed the tracer. At operation, multiple cortical adenomas, some of them large, were found in both adrenals.
Both patients with adrenocortical carcinoma failed to show adrenal uptake of the labelled com- pound.
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Discussion
Our results in patients with adrenocortical adenoma and carcinoma correlate with the results of others (Anderson and Beierwaltes, 1974; Jorgensen et al., 1975; Troncone et al., 1977). In cases of adenoma, the preponderant or total uptake of the radiophar- maceutical is on the side of the tumor, due to suppres- sion of pituitary ACTH by excess cortisol, resulting in subnormal stimulation of normal adrenocortical tissue. In patients with adrenocortical carcinoma, both adrenals are not visualized by scanning, due to low per cent uptake per gram of the neoplastic tissue (Moses et al., 1974).
The demonstration of mixed form (adenoma plus hyperplasia) and bilateral multiple adenomas by adrenal scintigraphy has not been previously reported. The dexamethasone suppression scanning has been introduced by Conn et al. (1972) for the evalua- tion of patients with primary aldosteronism, but has not been used in patients with Cushing’s syndrome.
Adrenal scintigraphy is a reliable technique for distinguishing between bilateral hyperplasia, ade- noma and carcinoma in Cushing’s syndrome. In bi- lateral adrenocortical hyperplasia there is symmetrical prominent activity in adrenal glands (Moses et al., 1974). Our patient with the mixed form (adenoma plus hyperplasia) showed a hyperplasia-like scin- tigraphic pattern, but the tumor bearing gland was comparatively larger on the scan, which helped the preoperative localization of the neoplasm.
It is reasonable to suggest that patients with bi- lateral multiple cortical adenomas would show the hyperplasia-like scintigraphic pattern. The dexametha- sone modified adrenal scintigraphy would reveal the bilateral autonomus function of the adrenal glands in such patients.
Thus, in some rare cases with Cushing’s syndrome, the scintigraphic image of the adrenal glands may be interpreted as “bilateral hyperplasia” while an adrenal tumor is present. In such patients, where there is a discrepancy between the scintigraphic pattern and the biochemical indexes of adrenal hyperfunction, the dexamethasone suppression scanning could be used as an adjunctive diagnostic procedure to rule out au- tonomus neoplastic tissue.
Our data, even though still limited confirms the validity of adrenal scintigraphy. However, the proce- dure is not yet widely used because of the present limitations and disadvantages of the scanning agent. These are : a) relatively high radiation dose to patients at the recommended activity of 1-2 mCi; b) the long time rquired for completion of the scan; and c) the relatively high cost of the agent.
The mechanism of concentration of the tracer in
the adrenal cortex probably concerns the fact that cholesterol represents the principal precursor of adre- nocortical steroids. In the human the effective half life of the labelled compound has been estimated to be 1.77-2.26 days, resulting in a total body radiation absorbed dose of 0.48-0.94 rad/mCi. Tissue distribu- tion studies on excised adrenal tissue have led to esti- mated absorbed radiation doses of 25-50 rad for 2 mCi of 1311-19-iodocholesterol (Beierwaltes et al., 1971 ; Lieberman et al., 1971).
Adrenal venous angiography has been an effective tool in the preoperative localization of adrenocortical adenomas. However, the procedure is not always suc- cessful and requires a great deal of experience. It is an invasive procedure, associated with discomfort and some morbidity, namely adrenal hemorrhage and permanent adrenal insufficiency (Conn et al., 1972). In contrast, imaging with radiocholesterol is a benign procedure without associated complications.
Despite the limitations mentioned, adrenal scinti- graphy with 131I-19-iodocholesterol applied to well selected patients should be a useful and often indis- pensable diagnostic procedure. In fact, adrenal scinti- graphy by itself can be conclusive in hyperfunctioning adenomas associated with Cushing’s syndrome.
References
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