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Abstract
The major applications for molecular imaging with PET in clinical practice concern cancer imaging. Undoubtedly, 18F-FDG represents the backbone of nuclear oncology as it remains so far the most widely employed positron emitter compound. The acquired knowledge on cancer features, however, allowed the recognition in the last decades of multiple metabolic or pathogenic pathways within the cancer cells, which stimulated the development of novel radiopharmaceuticals. An endless list of PET tracers, substantially covering all hallmarks of cancer, has entered clinical routine or is being investigated in diagnostic trials. Some of them guard significant clinical applications, whereas others mostly bear a huge potential. This chapter summarizes a selected list of non-FDG PET tracers, described based on their introduction into and impact on clinical practice.
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Beshr R, Isohashi K, Watabe T, Naka S, Horitsugi G, Romanov V, Kato H, Miyatake SI, Shimosegawa E, Hatazawa J. Preliminary feasibility study on differential diagnosis between radiation-induced cerebral necrosis and recurrent brain tumor by means of [ 18F]fluoro-borono-phenylalanine PET/CT. Ann Nucl Med 2018; 32:702-708. [PMID: 30194665 DOI: 10.1007/s12149-018-1296-2] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 08/30/2018] [Indexed: 12/15/2022]
Abstract
OBJECTIVES A previous study reported that a differential diagnosis between glioblastoma progression and radiation necrosis by 4-borono-2-[18F]-fluoro-phenylalanine ([18F]FBPA) PET can be made based on lesion-to-normal ratio of [18F]FBPA accumulation. Two-dimensional data acquisition mode PET alone system, with in-plane resolution of 7.9 mm and axial resolution of 13.9 mm, was used. In the current study, we aimed to confirm the differential diagnostic capability of [18F]FBPA PET/CT with higher PET spatial resolution by three-dimensional visual inspection and by measuring mean standardized uptake value (SUVmean), maximum SUV (SUVmax), metabolic tumor volume (MTV), and total lesion (TL) [18F]FBPA uptake. METHODS Twelve patients of glioma (9), malignant meningioma (1), hemangiopericytoma (1), and metastatic brain tumor (1) were enrolled. All had preceding radiotherapy. High-resolution three-dimensional data acquisition mode PET/CT with in-plane resolution of 4.07 mm and axial resolution of 5.41 mm was employed for imaging. Images were three-dimensionally analyzed using the PMOD software. SUVmean and SUVmax of lesion and normal brain were measured. Lesion MTV and TL FBPA uptake were calculated. The diagnostic accuracy of [18F]FBPA PET/CT in detecting recurrence (n = 6) or necrosis (n = 6) was verified by clinical follow-up. RESULTS All parameters showed significantly higher values for tumor recurrence than for necrosis. SUVmean in recurrence was 2.95 ± 0.84 vs 1.18 ± 0.24 in necrosis (P = 0.014); SUVmax in recurrence was 4.63 ± 1.23 vs 1.93 ± 0.44 in necrosis (P = 0.014); MTV in recurrence was 44.92 ± 28.93 mL vs 10.66 ± 8.46 mL in necrosis (P = 0.032); and mean TL FBPA uptake in recurrence was 121.01 ± 50.48 g vs 12.36 ± 9.70 g in necrosis (P = 0.0029). CONCLUSION In this preliminary feasibility study, we confirmed the possibility of differentiating tumor recurrence from radiation necrosis in patients with irradiated brain tumors by [18F]FBPA PET/CT using indices of SUVmean, SUVmax, MTV, and TL 18FBPA uptake.
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Affiliation(s)
- Rouaa Beshr
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan.,Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Kayako Isohashi
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Tadashi Watabe
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Sadahiro Naka
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Genki Horitsugi
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Victor Romanov
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan.,Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan
| | - Hiroki Kato
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan
| | - Shin-Ichi Miyatake
- Department of Neurosurgery, Osaka Medical College, Takatsuki, Osaka, Japan
| | - Eku Shimosegawa
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan.,Department of Molecular Imaging in Medicine, Osaka University Graduate School of Medicine, Suita, Osaka, Japan
| | - Jun Hatazawa
- Department of Nuclear Medicine and Tracer Kinetics, Osaka University Graduate School of Medicine, 2-2, Yamadaoka, Suita, Osaka, 565-0871, Japan. .,Immunology Frontier Research Center, Osaka University, Suita, Osaka, Japan.
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Abstract
BACKGROUND Cerebral radiation necrosis (RN) is a severe complication of radiotherapy for cerebral pathologies. This study discusses the radiographic and pathological features of 12 patients with RN and investigates the management strategy. METHODS Eleven patients with brain tumors, and one with cerebral cavernous angioma, treated by surgical resection or Gamma Knife alone before radiotherapy developed RN during follow-up. Surgical resection for the cerebral RN was performed in nine patients, and the other three patients received medical treatment. The clinical features, magnetic resonance imaging (MRI), surgical findings, and pathological sections are reviewed. RESULTS The diagnosis of RN was confirmed by histological study in all the patients; those with surgical and medical treatment recovered. CONCLUSION As a major complication of radiotherapy, from the clinical and neuroradiological points of view, RN may simulate tumor recurrence. Due to the increasing number of patients with RN who will need to be treated in future years, the definite diagnosis and appropriate treatment of RN remain critical.
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Nakajima R, Abe K, Momose M, Fukushima K, Matsuo Y, Kimura K, Kondo C, Sakai S. Optimization of scan initiation timing after 11C-methionine administration for the diagnosis of suspected recurrent brain tumors. Ann Nucl Med 2016; 31:190-197. [PMID: 27885545 DOI: 10.1007/s12149-016-1140-5] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/10/2016] [Accepted: 11/08/2016] [Indexed: 11/25/2022]
Abstract
OBJECTIVE 11C-Methionine (MET) positron emission tomography (PET) imaging is a valuable technique for the evaluation of primary and recurrent brain tumors. Many studies have used MET-PET for data acquisition starting at 20 min after the tracer injection, while others have used scan initiation times at 5-15 min postinjection. No previous studies have identified the best acquisition timing during MET-PET imaging for suspected recurrent brain tumors. Here we sought to determine the optimal scan initiating timing after MET administration for the detection of recurrent brain tumors. MATERIALS AND METHODS Twenty-three consecutive patients with suspected recurrent brain tumors underwent MET-PET examinations. Brain PET images were reconstructed from the four serial data sets (10-15, 15-20, 20-25, and 25-30 min postinjection) that were obtained using the list-mode acquisition technique. We determined the maximal standardized uptake values (SUVmax) of the target lesions and the target-to-normal-tissue ratios (TNRs), calculated as the SUVmax to the SUVmean of a region of interest placed on the normal contralateral frontal cortex. Target lesions without significant MET uptake were excluded. RESULTS Thirty-one lesions from 23 patients were enrolled. There were no significant differences in MET SUVmax or TNR values among the PET images that were reconstructed with the data extracted from the four phases postinjection. CONCLUSION The MET uptake in the suspected recurrent brain tumors was comparable among all data extraction time phases from 10 to 30 min postinjection. The scan initiation time of MET-PET at 10 min after the injection is allowable for the detection of recurrent brain tumors. The registration identification number of the original study is 1002.
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Affiliation(s)
- Reiko Nakajima
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Koichiro Abe
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan.
| | - Mitsuru Momose
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Kenji Fukushima
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Yuka Matsuo
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Ken Kimura
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Chisato Kondo
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
| | - Shuji Sakai
- Department of Diagnostic Imaging and Nuclear Medicine, Tokyo Women's Medical University, 8-1 Kawada-cho, Shinjuku-ku, Tokyo, 162-8666, Japan
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Matsunaga S, Shuto T, Takase H, Ohtake M, Tomura N, Tanaka T, Sonoda M. Semiquantitative Analysis Using Thallium-201 SPECT for Differential Diagnosis Between Tumor Recurrence and Radiation Necrosis After Gamma Knife Surgery for Malignant Brain Tumors. Int J Radiat Oncol Biol Phys 2013; 85:47-52. [DOI: 10.1016/j.ijrobp.2012.03.008] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/12/2011] [Revised: 03/02/2012] [Accepted: 03/02/2012] [Indexed: 12/27/2022]
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Abstract
The major application for PET imaging in clinical practice is represented by cancer imaging and (18)F-FDG is the most widely employed positron emitter compound. However, some diseases cannot be properly evaluated with this tracer and thus there is the necessity to develop more specific compounds. The last decades were a continuous factory for new radiopharmaceuticals leading to an endless list of PET tracers; however, just some of them guard diagnostic relevance in routine medical practice. This chapter describes a selected list of non-FDG PET tracers, basing on their introduction into and impact on clinical practice.
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Affiliation(s)
- Egesta Lopci
- Nuclear Medicine Unit, Humanitas Cancer Center, Rozzano, MI, Italy
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Okamoto S, Shiga T, Hattori N, Kubo N, Takei T, Katoh N, Sawamura Y, Nishijima K, Kuge Y, Tamaki N. Semiquantitative analysis of C-11 methionine PET may distinguish brain tumor recurrence from radiation necrosis even in small lesions. Ann Nucl Med 2010; 25:213-20. [PMID: 21188660 DOI: 10.1007/s12149-010-0450-2] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2010] [Accepted: 11/04/2010] [Indexed: 10/18/2022]
Abstract
OBJECTIVE (11)C-Methionine positron emission tomography (MET-PET) has been used to distinguish brain tumor recurrence from radiation necrosis. Because the spatial resolution of conventional PET scanners is low, partial volume effect (PVE) may decrease the detectability of small tumor recurrence. The aim of this study is to investigate the diagnostic value of MET-PET upon semiquantitative analyses in particular PVE-affected small lesions. METHODS First, we performed a phantom experiment to investigate what size lesion is affected by PVE. This study included 29 patients (33 lesions) suspected of recurrent brain tumors by magnetic resonance imaging (MRI) after radiation therapy. All of them received MET-PET. Semiquantitative analysis was performed using maximum standardized uptake value (SUVmax) and lesion-versus-normal ratio (L/N ratio). ROC analysis was also assessed about the diagnostic value of MET-PET. RESULTS From the result of the phantom experiment, lesions smaller than 20 mm in brain mode or smaller than 30 mm in whole-body mode were defined as PVE-affected lesions. Histological analysis or clinical follow-up confirmed the diagnosis of tumor recurrence in 22 lesions, and radiation necrosis in 11 lesions. L/N ratios of recurrence and necrosis for overall lesions were 1.98 ± 0.62 and 1.27 ± 0.28, respectively (p < 0.01). In the PVE-affected lesions, L/N ratio for recurrence (1.72 ± 0.44) was also significantly higher than that for necrosis (1.20 ± 0.11) (p < 0.01). On the ROC analysis for the PVE-affected lesions, the area under the curve for L/N ratio (0.897) was significantly higher than that for SUVmax (0.718) (p < 0.05). These areas under the curve were almost equal to that of overall lesions for L/N ratio (0.886) and for SUVmax (0.738). CONCLUSIONS Semiquantitative analysis of MET provided high diagnostic value even for PVE-affected small lesions. MET-PET enables early diagnosis of recurrence of brain tumor in the follow-up after the radiation therapy.
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Affiliation(s)
- Shozo Okamoto
- Department of Nuclear Medicine, Hokkaido University Graduate School of Medicine, North 15th, West 7th, Kitaku, Sapporo, 060-8638, Japan.
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Park KJ, Kang SH, Lee HK, Chung YG. Rapid progression of early delayed radiation effect in pleomorphic xanthoastrocytoma. J Korean Neurosurg Soc 2009; 46:564-7. [PMID: 20062573 DOI: 10.3340/jkns.2009.46.6.564] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/29/2009] [Revised: 03/23/2009] [Accepted: 10/26/2009] [Indexed: 11/27/2022] Open
Abstract
Early delayed radiation effects are known to occur within several months after completing radiotherapy for brain tumors. We present marked changes of magnetic resonance imaging (MRI) scan that occurred one month after radiotherapy in a patient with a pleomorphic xanthoastrocytoma, which was eventually diagnosed as an early delayed radiation effect. Such an early development of dramatic MRI change has not been reported in patients treated with radiotherapy for pleomorphic xanthoastrocytomas.
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Affiliation(s)
- Kyung Jae Park
- Department of Neurosurgery, Korea University College of Medicine, Seoul, Korea
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Terakawa Y, Tsuyuguchi N, Iwai Y, Yamanaka K, Higashiyama S, Takami T, Ohata K. Diagnostic Accuracy of 11C-Methionine PET for Differentiation of Recurrent Brain Tumors from Radiation Necrosis After Radiotherapy. J Nucl Med 2008; 49:694-9. [DOI: 10.2967/jnumed.107.048082] [Citation(s) in RCA: 275] [Impact Index Per Article: 17.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/16/2022] Open
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10
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Jackson EF, Esparza-Coss E, Wen X, Ng C, Daniel SL, Price RE, Rivera B, Charnsangavej C, Gelovani JG, Li C. Magnetic resonance imaging of therapy-induced necrosis using gadolinium-chelated polyglutamic acids. Int J Radiat Oncol Biol Phys 2007; 68:830-8. [PMID: 17379450 PMCID: PMC1997292 DOI: 10.1016/j.ijrobp.2007.01.011] [Citation(s) in RCA: 21] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2006] [Revised: 01/05/2007] [Accepted: 01/06/2007] [Indexed: 02/08/2023]
Abstract
PURPOSE Necrosis is the most common morphologic alteration found in tumors and surrounding normal tissues after radiation therapy or chemotherapy. Accurate measurement of necrosis may provide an early indication of treatment efficacy or associated toxicity. The purpose of this report is to evaluate the selective accumulation of polymeric paramagnetic magnetic resonance (MR) contrast agents--gadolinium p-aminobenzyl-diethylenetriaminepentaacetic acid-poly(glutamic acid) (L-PG-DTPA-Gd and D-PG-DTPA-Gd)--in necrotic tissue. METHODS AND MATERIALS Two different solid tumor models, human Colo-205 xenograft and syngeneic murine OCA-1 ovarian tumors, were used in this study. Necrotic response was induced by treatment with poly(L-glutamic acid)-paclitaxel conjugate (PG-TXL). T(1)-weighted spin-echo images were obtained immediately and up to 4 days after contrast injection and compared with corresponding histologic specimens. Two low-molecular-weight contrast agents, DTPA-Gd and oligomeric(L-glutamic acid)-DTPA-Gd, were used as nonspecific controls. RESULTS Initially, there was minimal tumor enhancement after injection of either L-PG-DTPA-Gd or D-PG-DTPA-Gd, but rapid enhancement after injection of low-molecular-weight agents. However, polymeric contrast agents, but not low-molecular-weight contrast agents, caused sustained enhancement in regions of tumor necrosis in both tumors treated with PG-TXL and untreated tumors. These data indicate that high molecular weight, rather than in vivo biodegradation, is necessary for the specific localization of polymeric MR contrast agents to necrotic tissue. Moreover, biotinylated L-PG-DTPA-Gd colocalized with macrophages in the tumor necrotic areas, suggesting that selective accumulation of L- and D-PG-DTPA-Gd in necrotic tissue was mediated through residing macrophages. CONCLUSIONS Our data suggest that MR imaging with PG-DTPA-Gd may be a useful technique for noninvasive characterization of treatment-induced necrosis.
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Affiliation(s)
- Edward F. Jackson
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Emilio Esparza-Coss
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Xiaoxia Wen
- Department of Experimental Diagnostic Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Chaan Ng
- Department of Diagnostic Radiology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Sherita L. Daniel
- Department of Pathology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Roger E. Price
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Belinda Rivera
- Department of Imaging Physics, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Chusilp Charnsangavej
- Department of Diagnostic Radiology, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Juri G. Gelovani
- Department of Experimental Diagnostic Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
| | - Chun Li
- Department of Experimental Diagnostic Imaging, The University of Texas M. D. Anderson Cancer Center, Houston, TX 77030
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Kashimura H, Inoue T, Beppu T, Ogasawara K, Ogawa A. Diffusion tensor imaging for differentiation of recurrent brain tumor and radiation necrosis after radiotherapy--three case reports. Clin Neurol Neurosurg 2006; 109:106-10. [PMID: 16793199 DOI: 10.1016/j.clineuro.2006.04.005] [Citation(s) in RCA: 34] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2005] [Revised: 03/24/2006] [Accepted: 04/03/2006] [Indexed: 11/24/2022]
Abstract
Fractional anisotropy (FA) is influenced by histological data such as cellularity, vascularity and/or fiber structure in astrocytic tumors. We describe two patients with tumor recurrence and one patient with radiation necrosis who were diagnosed using assessment of FA value. The assessment of FA value in enhanced lesions after radiotherapy may be able to differentiate radiation necrosis from tumor recurrence.
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Affiliation(s)
- Hiroshi Kashimura
- Department of Neurosurgery, Iwate Medical University School of Medicine, 19-1 Uchimaru, Morioka, Iwate, Japan.
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Hsu YC, Wang LF, Lee KW, Ho KY, Huang CJ, Kuo WR. Cerebral radionecrosis in patients with nasopharyngeal carcinoma. Kaohsiung J Med Sci 2006; 21:452-9. [PMID: 16302448 DOI: 10.1016/s1607-551x(09)70150-0] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/18/2022] Open
Abstract
This study involved seven patients with cerebral radionecrosis following radiation therapy for nasopharyngeal carcinoma (NPC). Their charts were reviewed and the relationship of extracranial malignancies to cerebral radionecrosis was investigated. The radiation dose ranged from 70 to 135 Gy, and the latency was from 6 to 39 months. Two of seven patients died of NPC-related complications during follow-up. The crude incidence of cerebral radionecrosis in patients with NPC was 0.93% in our series. Improvement of symptoms could be achieved by corticosteroid therapy, with or without surgery. In a review of the literature, there were 306 cases of cerebral radionecrosis in extracranial malignancies. The nasopharynx is the most common primary site in cerebral radionecrosis of extracranial malignancies, followed by the scalp and sinonasal tract. The 3-year overall survival rate in our series was 68.57%, as provided by the Kaplan-Meier product limited method. Cerebral radionecrosis in NPC patients should be differentiated from tumor recurrence, in order to apply the appropriate treatment.
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Affiliation(s)
- Ying-Che Hsu
- Department of Otolaryngology, Kaohsiung Medical University Chun-Ho Memorial Hospital, Taiwan
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Tsuyuguchi N, Sunada I, Iwai Y, Yamanaka K, Tanaka K, Takami T, Otsuka Y, Sakamoto S, Ohata K, Goto T, Hara M. Methionine positron emission tomography of recurrent metastatic brain tumor and radiation necrosis after stereotactic radiosurgery: is a differential diagnosis possible? J Neurosurg 2003; 98:1056-64. [PMID: 12744366 DOI: 10.3171/jns.2003.98.5.1056] [Citation(s) in RCA: 141] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/06/2022]
Abstract
OBJECT In this study the authors examined how to differentiate radiation necrosis from recurrent metastatic brain tumor following stereotactic radiosurgery by using positron emission tomography (PET) with L-[methyl-11C]methionine (MET). METHODS In 21 adult patients with suspected recurrent metastatic brain tumor or radiation injury, MET-PET scans were obtained. These patients had previously undergone stereotactic radiosurgery and subsequent contrast-enhanced magnetic resonance (MR) examinations before nuclear medicine imaging. Positron emission tomography images were obtained as a static scan of 10 minutes performed 20 minutes after injection of 370 MBq of MET. On MET-PET scans, the portion of the tumor with the highest accumulation of MET was selected as the region of interest (ROI), and the ratio of tumor tissue to normal tissue (T/N) was defined as the mean counts of radioisotope per pixel in the tumor divided by the mean counts per pixel in normal gray matter. The standardized uptake value (SUV) was calculated using the same ROI in the tumor. The accuracy of the MET-PET scan was evaluated by correlating findings with results of subsequent histological analysis (11 cases) or, in cases in which surgery or biopsy was not performed, with subsequent clinical course and MR imaging findings (10 cases). Histological examinations performed in 11 cases showed viable tumor cells with necrosis in nine and necrosis with no viable tumor cells in two. Another 10 cases were characterized as radiation necrosis because the patients exhibited stable neurological symptoms with no sign of massive enlargement of the lesion on follow-up MR images after 5 months. The mean T/N was 1.15 in the radiation necrosis group (12 cases) and 1.62 in the tumor recurrence group (nine cases). The mean SUV was 1.78 in the necrosis group and 2.5 in the recurrence group. There were statistically significant differences between the recurrence and necrosis groups in T/N and SUV. Furthermore, the borderline T/N value was 1,42 according to a 2 x 2 factorial table (high T/N or low T/N, recurrence or necrosis). From this result, the sensitivity and specificity of MET-PET scanning in detecting tumor recurrence were determined to be 77.8 and 100%, respectively. CONCLUSIONS The use of MET-PET scanning is a sensitive and accurate technique for differentiating between metastatic brain tumor recurrence and radiation necrosis following stereotactic radiosurgery. This study reveals important information for creating strategies to treat postradiation reactions.
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Affiliation(s)
- Naohiro Tsuyuguchi
- Department of Neurosurgery, Osaka City University Graduate School of Medicine, Abeno, Osaka, Japan.
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