Somatostatin receptor subtype 2 is expressed by supratentorial primitive neuroectodermal tumors of childhood and can be targeted for somatostatin receptor imaging.
OBJECTIVE
Although gliomas predominate among central nervous system (CNS) neoplasms in adulthood, embryonal tumors are the most common malignant brain tumors in children. Despite novel treatment approaches, including improved radiotherapy and high-dose chemotherapy, survival rates remain unsatisfactory. The timely diagnosis of residual or recurrent embryonal CNS tumors and thus the earliest possible time point for intervention is often hampered by inaccuracies of conventional imaging techniques. Novel and refined imaging methodologies are urgently needed.


METHODS
We have previously demonstrated the use of somatostatin receptor imaging (SRI) in the diagnosis of recurrent and residual medulloblastomas. Here, we evaluated somatostatin receptor type 2 (sst(2)) expression using an antibody in an array of CNS tumors of childhood. Eight high-grade gliomas, 4 atypical teratoid/rhabdoid tumors, 7 supratentorial primitive neuroectodermal tumors (stPNET), 1 medulloepithelioma (ME), and 8 ependymomas were screened. Tumors positive in vitro were additionally analyzed in vivo using SRI.


RESULTS
Abundant expression of somatostatin receptor type 2 in stPNET, a ME, and ependymomas warranted in vivo imaging of 7 stPNET, 1 rhabdomyosarcoma, 3 ependymomas, 1 ME, and 1 glioblastoma. Although SRI was positive in 6/7 stPNET, 1 rhabdomyosarcoma, and 1 ME, none of the ependymomas nor the glioblastoma could be imaged using SRI. In selected cases SRI was more sensitive in the detection of relapse than conventional imaging by magnetic resonance imaging and computed tomography.


CONCLUSIONS
SRI should be considered in the evaluation of residual or recurrent embryonal CNS tumors, especially stPNET. The strengths of SRI lie in the differentiation of reactive tissue changes versus residual or recurrent tumor, the detection of small lesions, and possibly in the distinction of stPNET from gliomas.
Frühwald
Michael C
MC
Department of Pediatric Hematology and Oncology, University Children's Hospital Muenster, Muenster, Germany. fruhwald@uni-muenster.de
Rickert
Christian H
CH
O'Dorisio
M Sue
MS
Madsen
Mark
M
Warmuth-Metz
Monika
M
Khanna
Geetika
G
Paulus
Werner
W
Kühl
Joachim
J
Jürgens
Heribert
H
Schneider
Peter
P
Müller
Hermann L
HL
D016543:Central Nervous System Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology; D002648:Child; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007150:Immunohistochemistry; D007223:Infant; D008297:Male; D018242:Neuroectodermal Tumors, Primitive / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D017481:Receptors, Somatostatin / Q000096:biosynthesis*; D015173:Supratentorial Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology*; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods
D017481:Receptors, Somatostatin; C093733:somatostatin receptor 2