Somatostatin receptor scintigraphy in central nervous system tumors: role of blood-brain barrier permeability.

UNLABELLED: Somatostatin receptors are expressed in meningiomas and low-grade gliomas, raising the hope that scintigraphy with 111In-DTPA-D-Phe1-octreotide might be helpful in the in vivo localization, differential diagnosis and postoperative/postradiotherapy brain tumor follow-up. METHODS: Indium-111-DTPA-D-Phe1-octreotide scintigraphy and brain scintigraphy using 99mTc-DTPA as a nonspecific tracer for blood-brain barrier integrity were simultaneously performed in 60 patients with CNS tumors using dual-isotope acquisition mode SPECT. For 23 patients, the scintigraphic findings were also compared with in vitro somatostatin receptor autoradiography of surgical biopsy specimens. RESULTS: In meningiomas (located outside the blood-brain barrier), the somatostatin receptor scan showed all tumors and scintigraphic signal intensity correlating with in vitro SSR density positive in all meningiomas. Less contrast was seen on 99mTc-DTPA scans. In all tumors inside the blood-brain barrier, the 111In-DTPA-D-Phe1-octreotide scan visualized the tumors with a disrupted blood-brain barrier, as seen by 99mTc-DTPA scintigraphy. Discrepancies, however, were observed between somatostatin receptor scintigraphy and in vitro receptor autoradiography. CONCLUSION: Combined somatostatin receptor and 99mTc-DTPA scintigraphy may be helpful for noninvasive differentiation between meningiomas and other CNS tumors. False-negative scans were observed as a result of shielding by the intact blood-brain barrier. Interpretation of negative and positive somatostatin receptor scans in CNS tumors must therefore be done with caution.

Arteriovenous shunt measurement during endovascular therapy for cerebrospinal lesions.

PURPOSE: To determine (a) whether superselective angioscintigraphy with technetium-99m macroaggregated albumin (99mTc-MAA) can be used for the evaluation of arteriovenous shunting in tumors and vascular malformations of the head and spine and (b) whether the amount of microparticles shunted is related to diagnosis, lesion size, or angiographic pattern. METHODS: Particles of 99mTc-MAA with a calibrated diameter of 25 to 50 microm were delivered intraarterially in feeders of head and spine tumors and vascular malformations in 38 patients. The first estimation of the proportion of particles reaching the lungs was made on-line in the angiography suite using a hand-held lead-shielded detector. Evaluation of the intralesional shunt (pulmonary shunt index, or PSI) was derived from quantitative gamma camera recordings of tumoral and pulmonary activity after the embolization procedure was complete. RESULTS: The PSI value ranged from 48% to 100% for vascular malformations and vascular tumors (n = 11), 82% to 95% for juvenile angiofibromas (n = 4), 63% to 70% for high-grade gliomas (n = 2), 0% to 50% for renal cell carcinoma metastases (n = 4), 0% to 86% for meningiomas (n = 11), and 0% to 36% for paragangliomas (n = 6). Angiographically, the presence of visible arteriovenous channels was predictive of a high PSI. In contrast, the presence of early venous drainage was associated with a wide PSI range. CONCLUSION: Superselective 99mTc-MAA angioscintigraphy of tumors and vascular malformations of the head and spine is a valuable method for quantifying an intralesional arteriovenous shunt before embolization.

Preoperative embolization of paragangliomas and angiofibromas. Measurement of intratumoral arteriovenous shunts.

OBJECTIVE: To determine if technetium Tc 99m-labeled macroaggregated albumin selective angioscintigraphy enables estimation of microparticle-arteriovenous shunt in branchial paragangliomas and nasopharyngeal angiofibromas. DESIGN: Technetium Tc 99m-labeled macroaggregated albumin particles with calibrated diameters between 25 and 50 microns were administered during selective catheterization of the feeding arteries in 4 branchial paragangliomas (glomus tumors) and 4 nasopharyngeal angiofibromas. Preliminary measures of the activity of the tumor region and of the lungs were obtained in the angiography suite using a hand-held detector. Without changing the position of the microcatheter, definitive embolization was performed. After endovascular treatment, scintigraphy was performed and the pulmonary shunt index was calculated with the use of a gamma camera and a dedicated computer program. RESULTS: The pulmonary shunt index varied between 0% and 36% for branchial paragangliomas (glomus tumors) and between 82% and 95% for angiofibromas. CONCLUSIONS: Our results provide new evidence that the incidence of microparticle-arteriovenous shunt in nasopharyngeal angiofibromas is much higher than in paragangliomas.

[The basis for radioiodine therapy in differentiated thyroid cancer]. / Grundlagen der Radiojodbehandlung von differenzierten Schilddrüsenkarzinomen.

Radioiodine therapy of differentiated thyroid cancer is based on the ability of these tumors to accumulate iodine, making them accessible to a metabolic treatment with I-131, a beta-emitting radioisotope leading to in intensive, highly selective and tumoricidal irradiation of such cells. Radioiodine ablation of thyroid remnants is performed few weeks after radical thyroid surgery and significantly decreases the risk of recurrence of thyroid cancer and the risk of death due to thyroid cancer. Even in recurrent or metastatic thyroid cancer, radioiodine treatment will often be curative or at least result in long term improvement, making differentiated thyroid cancers among the most curable cancers at present. In Switzerland, radioiodine treatment of thyroid cancer must be done in specialized nuclear medicine wards. Secondary effects are mild and mostly related to the symptoms of hypothyroidism. Recurrent or metastatic thyroid cancer often necessitates an interdisciplinary approach, including surgery, radioiodine therapy and sometimes external radiation therapy. Follow-up should be done in specialized centers in collaboration with the patient's family doctor.

[Long-term course of medullary thyroid gland carcinoma]. / Langzeitverlauf des medullären Schilddrüsenkarzinomes.

UNLABELLED: To obtain information on the outcome of medullary thyroid carcinoma (MTC) in the Berne area, a retrospective analysis of the 28 MTCs diagnosed by the Institute of Pathology of the University of Berne in the 25-year period between 1969 and 1994 was done. These 28 MTCs represented 2.4% of all thyroid malignancies diagnosed at the Bernese Institute of Pathology in the 25-year period mentioned above. 25 MTCs were sporadic and 3 associated with a multiple endocrine neoplasia (MEN) syndrome. Follow-up data were available from 27 of the 28 MTC patients. After a follow-up period of between 2 and 275 months 7 of these 27 patients had died form the MTC (among them all 4 patients with T4 tumors) and two were alive with tumor. 18 patients, including all 14 patients with T1 or T2 tumors without lymph node or distant metastases at the time of diagnosis, were alive and without evidence of tumor at the end of the follow-up period. CONCLUSIONS: MTCs are rare malignant tumors and comprise only a small fraction of all thyroid carcinomas in the Berne area. Most MTCs were sporadic, only a small minority was associated with a MEN syndrome. The TNM stage was the most important prognostic factor for patient survival. These data are in accordance with the results of similar MTC surveys done in other areas.

Noninvasive differentiation of meningiomas from other brain tumours using combined 111Indium-octreotide/99mtechnetium-DTPA brain scintigraphy.

We have studied prospectively 47 patients with CNS tumours including 16 meningiomas and 33 other tumours using combined 111In-octreotide and 99mTc-DTPA brain scintigraphy. 111In-octreotide scintigraphy was used to image somatostatin receptors (SSR) and 99mTc-DTPA scintigraphy was used to assess the integrity of the blood-brain barrier (BBB). A total of 32 tumours (65%) were detected. All SSR positive tumours also had positive 99mTc-DTPA scans and all SSR negative tumours were negative on 99mTc-DTPA scans. Among the tumours located outside the BBB, all meningiomas and two out of six schwannomas were positive on combined SSR/99mTc-DTPA scintigraphy. Among the tumours located inside the BBB, seven out of nine gliomas grade I-III were negative, whereas all glioblastomas were positive. Other positive tumours included one malignant non-Hodgkin lymphoma and two cerebral metastases. SSR scintigraphy alone was non-specific in the diagnosis of meningiomas, as 16 non-meningiomatous tumours also had positive SSR scans probably due to a breakdown of the BBB (excluding the malignant lymphoma). Measuring the tumour-to-background ratio on SSR scans improved specificity, but sensitivity was decreased below 70% because some meningiomas were only slightly positive. Only the ratio of SSR scintigraphy to conventional 99mTc-DTPA brain scintigraphy (SSR-to-BS index) allowed a reliable differentiation of meningiomas from other CNS tumours, most notable from schwannomas (sensitivity: 94%; specificity: 100%). Our results support the usefulness of combined SSR and conventional brain scintigraphy in the noninvasive pre-operative diagnosis of meningiomas.

Diagnostic angioscintigraphic evaluation of malignant hepatic tumors before catheter embolization: determination of shunt, flow distribution, and reflux.

PURPOSE: The aim of this study was to evaluate quantitatively arteriovenous shunts in malignant liver tumors by injection of 99mTc macroaggregates of albumin (MAA) into the tumor-feeding artery after selective catheterization. METHODS: In 40 patients with malignant liver tumors (33 hepatocellular carcinomas and 7 metastases of colorectal cancer), a mean dose of 200 MBq 99mTC MAA was injected arterially during angiography. The embolized area and the lungs were then visualized using a gamma camera. A dedicated computer program calculated pulmonary shunt rates. RESULTS: The majority of patients (n = 30) with hepatocellular carcinoma showed small shunts varying from 0 to 15%; only 3 of these patients had shunts ranging from 18% to 37%. In patients with colorectal carcinoma metastases (n = 7) the shunt varied from 0 to 3% (2 +/- 1%), probably due to a physiological shunt in normal liver tissue in the embolized area. Importantly, the degree of shunt found bore no correlation to the tumor volume or to the pattern of vascularity on angiography. CONCLUSION: Diagnostic angioscintigraphy is a useful tool for pretherapeutic evaluation of the capacity of an individual tumor to retain particles and to measure extratumoral shunting; these are essential for therapy planning, as they can help to increase the safety and effectiveness of embolization.