PET Identifies Transitional Metabolic Change in the Spinal Cord Following a Subthreshold Dose of Irradiation

Olga ÉSIK1, Miklós EMRI2, Szabolcs SZAKÁLL Jr2, Hans HERZOG3, Géza SÁFRÁNY4, Erzsébet LENGYEL5, András BOÉR6, Gabriella LISZKAY7, Lajos TRÓN8, Zsolt LENGYEL2, Imre REPA9

1Department of Oncotherapy, Pécs University of Sciences, Pécs, Hungary
2PET Center, University of Debrecen, Debrecen, Hungary
3PET Laboratory, Institute of Medicine, Research Center, Jülich, Germany
4National Research Institute for Radiobiology and Radiohygiene, Budapest, Hungary
5Section of Oncotherapy, Department of Radiology, Semmelweis University, Budapest, Hungary
6Department of Head and Neck Surgery, National Institute of Oncology, Budapest, Hungary
7Department of Dermatology, National Institute of Oncology, Budapest, Hungary
8PET Study Group of the Hungarian Academy of Sciences, Debrecen, Hungary
9Department of Diagnostic Imaging and Oncoradiology, University of Kaposvár, Kaposvár, Hungary


Positron emission tomographic (PET) investigations were performed to obtain in vivo information on symptomless radiation-induced pathological changes in the human spinal cord. PET investigations were carried out prior to radiotherapy and during the regular follow-up in an early hypopharyngeal cancer patient (the spinal cord was irradiated with a biologically effective dose of 80 Gy2), with [18F]fluorodeoxyglucose (FDG), [11C]methionine and [15O]butanol as tracers; radiosensitivity and electroneuronographic (ENG) studies were also performed. A very low background FDG accumulation (mean standardized uptake values, i.e. SUV: 0.84) was observed in the spinal cord before the initiation of radiotherapy. An increased FDG uptake was measured 2 months after the completion of radiotherapy (mean SUV: 1.69), followed by a fall-off, as measured 7 months later (mean SUV: 1.21). By 44 months after completion of irradiation, the FDG accumulation in the irradiated segments of the spinal cord had decreased to a level very close to the initial value (mean SUV: 1.11). The simultaneous [15O]butanol uptake results demonstrated a set of perfusion changes similar to those observed in connection with the FDG accumulation. The patient exhibited an extremely low [11C]methionine uptake within the irradiated and the nonirradiated spinal cord during the clinical course. She has not had any neurological symptoms, and the results of central ENG measurements before radiotherapy and 2 months following its completion proved normal. Radiobiological investigations did not reveal unequivocal signs of an increased radiosensitivity. A transitory increased spinal cord FDG uptake following radiotherapy may be related to the posttherapeutic mild inflammatory and regenerative processes. The normal [11C]methionine accumulation observed is strong evidence against intensive cell proliferation. The high degree of normalization of the temporarily increased FDG uptake of the irradiated spinal cord segments by 44 months is in good agreement with the results of monkey studies, which demonstrated a nearly complete recovery from radiation-induced spinal cord injury. Pathology & Oncology Research, Vol 10, Nr 1, 42-46, 2004

Key words: radiotherapy; spinal cord; positron emission tomography; [18F]fluorodeoxyglucose; [11C]methionine; [15O]butanol; radiobiology

Received: Jan 20, 2004; accepted: Feb 20, 2004
Correspondence: Olga ÉSIK, Department of Oncotherapy, Pécs University of Sciences, Édesanyák útja 17. Pécs H-7624, Hungary; Tel: 36-72-536080, Fax: 36-72-536481; E-mail:

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