THE ACCURACY OF [18F]FLUORODEOXYGLUCOSE POSITRON EMISSION TOMOGRAPHY AS CONFIRMED BY BIOPSY IN THE DIAGNOSIS OF SPINE METASTASES IN A CANCER POPULATION

Neurosurgery ◽  
2009 ◽  
Vol 64 (1) ◽  
pp. 107-114 ◽  
Author(s):  
Ilya Laufer ◽  
Eric Lis ◽  
Leszek Pisinski ◽  
Timothy Akhurst ◽  
Mark H. Bilsky
Keyword(s):  
Solid Tumors ◽  
Fdg Pet ◽  
Needle Biopsy ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
Computed Tomographic ◽  
Positron Emission ◽  
History Of ◽  
The Mean

Abstract OBJECTIVE To determine the accuracy of [18F]fluorodeoxyglucose (FDG) positron emission tomography (PET) in the diagnosis of vertebral metastases in patients with cancer using needle-biopsy results and patient follow-up data. METHODS A retrospective chart review of all patients who underwent a needle biopsy of a spinal lesion and underwent FDG-PET within 6 weeks of the biopsy was performed. Biopsy results and magnetic resonance imaging and computed tomographic appearance of the biopsied lesion, as well as long-term clinical follow-up data, were recorded for each patient. A total of 82 patients with solid tumors and hematological spine metastases were included in this study. RESULTS The mean standardized uptake values of lesions with active cancer were 7.1 and 2.1 in benign lesions (P < 0.02). In patients with metastatic solid tumors, the mean standardized uptake value was 7.3. Stratification of solid tumor lesions according to whether they had a sclerotic appearance on computed tomographic scans showed that FDG-PET was a significantly better predictor of cancer status in lytic or mixed lesions. In patients with a history of solid tumors, there was 100% concordance between the FDG-PET and needle-biopsy diagnoses in nonsclerotic lesions, when the standardized uptake value cutoff of 2 was used. CONCLUSION FDG-PET is an accurate screening test for vertebral metastases in cancer patients. It is especially accurate in patients with nonsclerotic vertebral lesions and a history of solid malignancy.

Usefulness of Positron Emission Tomography Using 18F-FDG Performed At Diagnosis and During Initial Chemotherapy for Imaging Primary Central Nervous System Lymphoma: A 24 Immunocompetent patient's Study.

Blood ◽  
2011 ◽  
Vol 118 (21) ◽  
pp. 1597-1597 ◽  
Author(s):  
Herve Ghesquieres ◽  
Céline Ferlay ◽  
Bertrand Richioud ◽  
Vanina Isnardi ◽  
Emmanuelle Nicolas-Virlizier ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Fdg Pet ◽  
Central Nervous System Lymphoma ◽  
Emission Tomography ◽  
Positron Emission ◽  
Systemic Spread ◽  
Pet Ct ◽  
The Mean ◽  
Fdg Pet Ct

Abstract Abstract 1597 Background: Primary central nervous system lymphoma (PCNSL) is a rare brain tumor potentially curable by chemotherapy alone or a combination of chemotherapy and radiation therapy. At staging, gadolinium-enhanced magnetic resonance imaging (MRI) is the standard method to evaluate CNS lesions and computed tomography (CT) is perform at diagnosis to detect the presence of a systemic disease. The initial tumor response to therapy is usually assessed by MRI. At present, there are no established imaging markers of prognosis in patients with PCNSL. Positron emission tomography (PET) using 18F-Fluorodeoxyglucose (FDG) is routinely used for the initial staging and the evaluation of treatment response in systemic Diffuse Large B-cell Lymphoma (DLBCL). In PCNSL, the clinical relevance of positron emission tomography FDG PET/CT is not well known. The aim of our study was to determine the added value of FDG PET/CT in the management of PCNSL performed at diagnosis and during initial treatment to assess whether it could predict the outcome of PCNSL patients. Patients and methods: From august 2008 to may 2011, we enrolled 24 consecutive PCNSL immunocompetent patients with histological proven DLBCL who underwent FDG PET/CT before specific treatment. The mean age of patients was 63.7 years (range, 51.7–78.8). Follow-up FDG PET/CT examinations were performed in 14 of them (58%) after 2 cycles of chemotherapy and in patients who relapsed. All PET images were acquired 1 hour after FDG injection and interpreted qualitatively and semi quantitatively by 2 nuclear medicine physician. The maximum standard uptake value (maxSUV) corrected to body weight and injected FDG activity was measured for each patient into the most hypermetabolic CNS lesion (TmaxSUV). The results were compared to the clinical and conventional imaging data. The correlation between TmaxSUV and respectively the Progression Free Survival (PFS) and Overall Survival (OS) was statistically analysed. We also evaluated for 15 patients, the correlation between the Ki67 index on tumors and TmaxSUV. Results: All the patients presented with brain lesions. The spinal cord was also involved in 1 of them. The sensitivity of FDG PET/CT for the detection of CNS lesions was 91.7 %. Two out of 24 patients were considered as false negative. The mean TmaxSUV was 13.9 +/− 9.3 (range, 4.9–38). FDG PET/CT found systemic spread of lymphoma in 2 patients (8.3%). Follow-up ranged from 3.2 to 33.8 months (mean, 20.6 months). After 2 cycles of chemotherapy, FDG PET/CT was considered as negative in 14/14 patients whereas gadolinium-enhanced MRI showed lesions with residual contrast-enhancement in 7 of them. Four patients who were PET- and MRI + after 2 cycles of chemotherapy relapsed exclusively into the CNS (n=2) and/or outside (n=2). FDG PET/CT showed all the sites of relapse. At last follow-up, 18 patients were alive and six died of progressive disease. No correlation between TmaxSUV at diagnosis and PFS (P =.15), OS (P =.14) and Ki67 index was respectively observed. Conclusions: Although the physiologic glucose metabolism in normal brain tissue is high, FDG PET/CT has a good sensitivity to detect PCNSL. FDG PET/CT could be useful to detect any systemic spread of PCNSL at staging and is able to diagnose disease relapse. Pretreatment Tmax SUV is not correlated with PFS and OS in our study. Moreover, FDG PET/CT seems not to be reliable for the prediction of relapse when it is performed after 2 cycles of chemotherapy. Others type of TEP tracers need to be study in PCNSL for response assessment and the prediction of patient's outcome. Disclosures: No relevant conflicts of interest to declare.

Prediction of Patient Outcome With 2-Deoxy-2-[18F]fluoro-D-Glucose-Positron Emission Tomography Early During Radiotherapy for Locally Advanced Cervical Cancer

2009 ◽  
Vol 19 (9) ◽  
pp. 1600-1605 ◽  
Author(s):  
Maria Bjurberg ◽  
Elisabeth Kjellén ◽  
Tomas Ohlsson ◽  
Pär-Ola Bendahl ◽  
Eva Brun
Keyword(s):  
Cervical Cancer ◽  
Fdg Pet ◽  
Locally Advanced ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
Advanced Cervical Cancer ◽  
Maximum Standardized Uptake Value ◽  
Locally Advanced Cervical Cancer ◽  
Positron Emission

Introduction:It is difficult to assess the individual response of locally advanced cervical cancer to chemoradiation therapy during the course of treatment. We have investigated the predictive value of positron emission tomography (PET) with 2-deoxy-2-[18F]fluoro-D-glucose (FDG) early during treatment in relation to progression-free survival.Methods:This prospective single-center clinical trial included women with locally advanced cervical cancer from 2004 to 2008. 2-Deoxy-2-[18F]fluoro-D-glucose-PET/computed tomography was performed at baseline, during the third week of treatment and, finally, 3 months after the completion of treatment. The images were evaluated visually, semiquantitatively with the maximum standardized uptake value, and by calculating the metabolic rate of FDG. Thirty-two patients were eligible for full evaluation.Results:The median follow-up time was 28 months (range, 5-53 months). Visual metabolic complete response on FDG-PET, after a mean irradiation dose of 23 Gy (range, 16-27 Gy), was found in 7 patients, none of which relapsed. Eleven of the 25 patients with remaining malignant hypermetabolism on the second FDG-PET relapsed. Neither maximum standardized uptake value nor metabolic rate of FDG could further discriminate between patients with low risk and patients with high risk of relapse. The follow-up FDG-PET performed 3 months after the completion of treatment identified a group of patients with poor prognosis.Conclusions:In conclusion, FDG-PET early during chemoradiation therapy identified a small number of patients with an excellent prognosis. However, FDG-PET at this early point in time during treatment failed to predict the outcome for most patients. Future clinical trials to determine the optimal timing of predictive FDG-PET are thus warranted.

Usefulness of positron emission tomography for differentiating gliomas according to the 2016 World Health Organization classification of tumors of the central nervous system

2020 ◽  
Vol 133 (4) ◽  
pp. 1010-1019 ◽  
Author(s):  
Hiroaki Takei ◽  
Jun Shinoda ◽  
Soko Ikuta ◽  
Takashi Maruyama ◽  
Yoshihiro Muragaki ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Pet Imaging ◽  
Who Classification ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
World Health ◽  
Pet Tracers ◽  
Positron Emission ◽  
Significant Difference ◽  
The Mean

OBJECTIVEPositron emission tomography (PET) is important in the noninvasive diagnostic imaging of gliomas. There are many PET studies on glioma diagnosis based on the 2007 WHO classification; however, there are no studies on glioma diagnosis using the new classification (the 2016 WHO classification). Here, the authors investigated the relationship between uptake of 11C-methionine (MET), 11C-choline (CHO), and 18F-fluorodeoxyglucose (FDG) on PET imaging and isocitrate dehydrogenase (IDH) status (wild-type [IDH-wt] or mutant [IDH-mut]) in astrocytic and oligodendroglial tumors according to the 2016 WHO classification.METHODSIn total, 105 patients with newly diagnosed cerebral gliomas (6 diffuse astrocytomas [DAs] with IDH-wt, 6 DAs with IDH-mut, 7 anaplastic astrocytomas [AAs] with IDH-wt, 24 AAs with IDH-mut, 26 glioblastomas [GBMs] with IDH-wt, 5 GBMs with IDH-mut, 19 oligodendrogliomas [ODs], and 12 anaplastic oligodendrogliomas [AOs]) were included. All OD and AO patients had both IDH-mut and 1p/19q codeletion. The maximum standardized uptake value (SUV) of the tumor/mean SUV of normal cortex (T/N) ratios for MET, CHO, and FDG were calculated, and the mean T/N ratios of DA, AA, and GBM with IDH-wt and IDH-mut were compared. The diagnostic accuracy for distinguishing gliomas with IDH-wt from those with IDH-mut was assessed using receiver operating characteristic (ROC) curve analysis of the mean T/N ratios for the 3 PET tracers.RESULTSThere were significant differences in the mean T/N ratios for all 3 PET tracers between the IDH-wt and IDH-mut groups of all histological classifications (p < 0.001). Among the 27 gliomas with mean T/N ratios higher than the cutoff values for all 3 PET tracers, 23 (85.2%) were classified into the IDH-wt group using ROC analysis. In DA, there were no significant differences in the T/N ratios for MET, CHO, and FDG between the IDH-wt and IDH-mut groups. In AA, the mean T/N ratios of all 3 PET tracers in the IDH-wt group were significantly higher than those in the IDH-mut group (p < 0.01). In GBM, the mean T/N ratio in the IDH-wt group was significantly higher than that in the IDH-mut group for both MET (p = 0.034) and CHO (p = 0.01). However, there was no significant difference in the ratio for FDG.CONCLUSIONSPET imaging using MET, CHO, and FDG was suggested to be informative for preoperatively differentiating gliomas according to the 2016 WHO classification, particularly for differentiating IDH-wt and IDH-mut tumors.

scholarly journals 68Ga-DOTATOC PET/CT Follow Up after Single or Hypofractionated Gamma Knife ICON Radiosurgery for Meningioma Patients

2021 ◽  
Vol 11 (3) ◽  
pp. 375
Author(s):  
Fabio Barone ◽  
Francesco Inserra ◽  
Gianluca Scalia ◽  
Massimo Ippolito ◽  
Sebastiano Cosentino ◽  
...  
Keyword(s):  
Gamma Knife ◽  
Case Series ◽  
Biological Response ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
Tumor Diameter ◽  
Relative Percentage ◽  
Positron Emission ◽  
Pet Ct

68Ga-DOTATOC represents a useful tool in tumor contouring for radiosurgery planning. We present a case series of patients affected by meningiomas on who we performed 68Ga-DOTATOC positron emission tomography (PET)/CT pre-operatively, a subgroup of which also underwent a post-operative 68Ga-DOTATOC PET/CT to evaluate the standardized uptake value (SUV) modification after Gamma Knife ICON treatment in single or hypofractionated fractions. Twenty patients were enrolled/included in this study: ten females and ten males. The median age was 52 years (range 33–80). The median tumor diameter was 3.68 cm (range 0.12–22.26 cm), and the median pre-radiotherapy maximum SUV value was 11 (range 2.3–92). The average of the relative percentage changes between SUVs at baseline and follow up was −6%, ranging from −41% to 56%. The SUV was reduced in seven out of 12 patients (58%), stable in two out of 12 (17%), and increased in three out of 12 (25%), suggesting a biological response of the tumor to the Gamma Knife treatment in most of the cases. 68Ga-DOTATOC-PET represents a valuable tool in assessing the meningioma diagnosis for primary radiosurgery; it is also promising for follow-up assessment.

scholarly journals Relationship between tumor mutational burden and maximum standardized uptake value in 2-[18F]FDG PET (positron emission tomography) scan in cancer patients

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Amin Haghighat Jahromi ◽  
Donald A. Barkauskas ◽  
Matthew Zabel ◽  
Aaron M. Goodman ◽  
Garret Frampton ◽  
...  
Keyword(s):  
Fdg Pet ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
Maximum Standardized Uptake Value ◽  
Tissue Biopsy ◽  
Mutational Burden ◽  
Positron Emission ◽  
Pet Ct ◽  
Tumor Mutational Burden ◽  
Fdg Pet Ct

Abstract Purpose Deriving links between imaging and genomic markers is an evolving field. 2-[18F]FDG PET/CT (18F-fluorodeoxyglucose positron emission tomography–computed tomography) is commonly used for cancer imaging, with maximum standardized uptake value (SUVmax) as the main quantitative parameter. Tumor mutational burden (TMB), the quantitative variable obtained using next-generation sequencing on a tissue biopsy sample, is a putative immunotherapy response predictor. We report the relationship between TMB and SUVmax, linking these two important parameters. Methods In this pilot study, we analyzed 1923 patients with diverse cancers and available TMB values. Overall, 273 patients met our eligibility criteria in that they had no systemic treatment prior to imaging/biopsy, and also had 2-[18F]FDG PET/CT within 6 months prior to the tissue biopsy, to ensure acceptable temporal correlation between imaging and genomic evaluation. Results We found a linear correlation between TMB and SUVmax (p < 0.001). In the multivariate analysis, only TMB independently correlated with SUVmax, whereas age, gender, and tumor organ did not. Conclusion Our observations link SUVmax in readily available, routinely used, and noninvasive 2-[18F]FDG PET/CT imaging to the TMB, which requires a tissue biopsy and time to process. Since higher TMB has been implicated as a prognostic biomarker for better outcomes after immunotherapy, further investigation will be needed to determine if SUVmax can stratify patient response to immunotherapy.

Spine Infections: the role of Fluorodeoxyglucose Positron Emission Tomography (FDG PET) in the context of the actual diagnosis guideline

2021 ◽  
Vol 17 ◽  
Author(s):  
Luca Boriani ◽  
Eleonora Zamparini ◽  
Mauro Albrizio ◽  
Francesca Serani ◽  
Giovanni Ciani ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Health Care Professionals ◽  
Fdg Pet ◽  
Emission Tomography ◽  
Correct Treatment ◽  
Positron Emission ◽  
Microbiological Agents ◽  
Current Guidelines

: Spondylodiscitis is an infectious process which requires numerous health care professionals in order to be clearly diagnosed and eventually, successfully treated. It implies a variety of microbiological agents and condition; during the diagnostic workup it is difficult to correctly identify them, and the clinician has to rapidly choose the most correct treatment, in order to avoid permanent injuries to the patient. In this context it comes our review work: based on current guidelines and literature available we wanted to deeply understand the most proper use of Positron Emission Tomography with 18-Fluoro-deossi-glucose (FDG PET) in a patient with the suspect of spondylodiscitis. We wanted to review the role of FDG PET in the spondylodiscitis diagnosis and follow up in the context of the current guidelines.

Prospective Study of Fluorodeoxyglucose–Positron Emission Tomography Imaging of Lymph Node Basins in Melanoma Patients Undergoing Sentinel Node Biopsy

1999 ◽  
Vol 17 (5) ◽  
pp. 1508-1508 ◽  
Author(s):  
Jeffrey D. Wagner ◽  
Donald Schauwecker ◽  
Darrell Davidson ◽  
John J. Coleman III ◽  
Scott Saxman ◽  
...  
Keyword(s):  
Lymph Node ◽  
Sentinel Node ◽  
Lymph Node Metastases ◽  
Fdg Pet ◽  
Regional Lymph Node ◽  
Emission Tomography ◽  
Node Biopsy ◽  
Positron Emission ◽  
Node Metastases

PURPOSE: To prospectively compare positron emission tomography (PET) imaging of regional lymph node basins to sentinel node biopsy (SNB) in patients with American Joint Committee on Cancer (AJCC) stage I, II, and III melanoma localized to the skin. METHODS: Patients with cutaneous melanoma with Breslow's depth greater than 1 mm (AJCC T2-4N0M0) or localized regional cutaneous recurrence (TxN2bM0) underwent whole-body imaging of glucose metabolism with fluorodeoxyglucose (FDG) PET followed by SNB. PET scans were interpreted in a blinded fashion and compared with histologic analyses of SNB specimens and clinical follow-up examination. Nodal tumor volumes were estimated. RESULTS: Eighty-nine lymph node basins were evaluated by FDG-PET and SNB in 70 assessable patients. Eighteen patients (25.7%) had lymph node metastases at the time of FDG-PET imaging: 17 proved by SNB (24.3%) and one by follow-up examination (1.4%). Median tumor volume in positive sentinel node basins was 4.3 mm3 (range, 0.07 to 523 mm3). Sensitivity of SNB for detection of occult regional lymph node metastases was 94.4%, specificity was 100%, positive predictive value (PPV) was 100%, and negative predictive value (NPV) was 98.6%. Sensitivity of FDG-PET was 16.7%, specificity was 95.8%, PPV was 50%, and NPV was 81.9%. At a median follow-up duration of 16.6 months, seven patients (10%) developed recurrent disease. PET predicted one recurrence (14.3%) in a node basin missed by SNB. CONCLUSION: FDG-PET is an insensitive indicator of occult regional lymph node metastases in patients with melanoma because of the minute tumor volumes in this population. FDG-PET does not have a primary role for staging regional nodes in patients with clinically localized melanoma.

scholarly journals Positron Emission Tomography as a Surrogate Marker for Evaluation of Treatment Response in Patients with Desmoid Tumors under Therapy with Imatinib

2013 ◽  
Vol 2013 ◽  
pp. 1-7 ◽  
Author(s):  
Bernd Kasper ◽  
Antonia Dimitrakopoulou-Strauss ◽  
Lothar R. Pilz ◽  
Ludwig G. Strauss ◽  
Christos Sachpekidis ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Progressive Disease ◽  
Surrogate Marker ◽  
Standardized Uptake Value ◽  
Response Prediction ◽  
Emission Tomography ◽  
Desmoid Tumors ◽  
Positron Emission ◽  
The Mean ◽  
Magnetic Resonance Imaging Mri

We used 2-deoxy-2-[18F] fluoro-D-glucose (FDG) positron emission tomography (PET) to evaluate patients with desmoid tumors undergoing therapy with imatinib. The study included 22 patients with progressive disease (PD) of a biopsy proven desmoid tumor treated orally with imatinib 800 mg daily. Patients were examined using PET prior to onset of therapy and during treatment. Restaging was performed in parallel using computed tomography (CT) and/or magnetic resonance imaging (MRI). Outcome of 22 evaluable patients was as follows: five patients with partial response (PR); twelve patients with stable disease (SD) accounting for 77% with non-progressive disease; five patients showed PD. A 30% decrease of the mean average standardized uptake value (SUV) of sequential PET examinations could be demonstrated; no patient demonstrated a substantial increase in SUV. Patients with PR/SD were matched to a group of nonprogressive disease and tested versus PD. The initial average SUV and seem to be candidates for a response prediction with an approximate -value of0.06553and0.07785, respectively. This is the first larger series of desmoid patients monitored using PET showing that early SUV changes may help to discriminate responders from nonresponders and, thus, to decide whether imatinib therapy should be continued.

scholarly journals Trichoepithelioma Arising in an Ovarian Mature Cystic Teratoma

2016 ◽  
Vol 2016 ◽  
pp. 1-5
Author(s):  
Takashi Suzuki ◽  
Satoru Nakayama ◽  
Haruka Muto ◽  
Shinichi Shimizu ◽  
Yoshiro Otsuki ◽  
...  
Keyword(s):  
Fdg Pet ◽  
Cystic Teratoma ◽  
Standardized Uptake Value ◽  
Japanese Woman ◽  
Mature Cystic Teratoma ◽  
Outer Root Sheath ◽  
Epithelial Tumor ◽  
Positron Emission ◽  
Old Japanese

Here, we report an extremely rare case of trichoepithelioma (TE)—a benign epithelial tumor originating from the outer root sheath of a hair follicle—arising in an ovarian mature cystic teratoma (MCT) with fluorodeoxyglucose-positron emission tomography (FDG-PET) findings. A 48-year-old Japanese woman presented to our hospital for her annual follow-up of adenomyosis. Ultrasonography and magnetic resonance imaging revealed a left ovarian tumor with irregular-shaped septum, which was suspicious of malignancy. However, tumor marker levels were within normal range. On FDG-PET, the maximum standardized uptake value (SUVmax) of the tumor was 2.9. Laparotomy with left salpingooophorectomy was performed. Pathologic examination revealed the probability of TE, rather than basal cell carcinoma (BCC), arising in an ovarian MCT. After five years of follow-up, the patient had no sign of recurrence. The FDG-PET SUVmax was low in TE, as with other benign tumor. However, future investigation is needed to evaluate the findings of FDG-PET imaging in TE cases.

The Relevance of Increased Tonsil Uptake When Restaging Lymphoma with Positron Emission Tomography

Blood ◽  
2010 ◽  
Vol 116 (21) ◽  
pp. 3133-3133
Author(s):  
Javier Munoz ◽  
Belisario Arango ◽  
Jessica Schering ◽  
James Morrison ◽  
Ishani Dalal ◽  
...  
Keyword(s):  
Positron Emission Tomography ◽  
Conflicts Of Interest ◽  
Standardized Uptake Value ◽  
Emission Tomography ◽  
Invasive Approach ◽  
Fdg Uptake ◽  
Tonsillar Tissue ◽  
Positron Emission ◽  
Lymphomatous Involvement ◽  
The Mean

Abstract Abstract 3133 Introduction: Significant tonsil uptake is sometimes observed in F-18 fluorodeoxyglucose (FDG) positron emission tomography (PET) after treatment. Some patients undergo tonsillectomy or FNA (fine needle aspiration) to rule out malignant involvement particularly when management depends on restaging (Figure 1). Our study describes the incidence and degree of tonsil FDG uptake in a large group of lymphoma patients that underwent PET scanning. Patients and Methods: Single institution, retrospective chart review by ICD code, 617 lymphoma patients that underwent PET at our institution from 2004 to 2009. Results of PET were compared to pathological diagnosis of tonsillectomy (Table 1) or FNA biopsy (Table 2) when available which was performed at physician's discretion. Patients that were diagnosed with lymphoma during restaging studies performed for a different primary malignancy were excluded. Results and Discussion: All 8 tonsillectomies and FNA biopsies performed after a restaging PET that showed increased tonsil uptake were negative for malignancy (Figure 2). All of these 8 patients had an initial previous PET that did not show increased tonsil uptake and also these 8 patients remained in remission from their lymphoma after the procedure was performed. In contrast, 6 out of 7 patients that underwent tonsillectomy or FNA at diagnosis were positive for malignancy (Table 3). Differences among tonsil FDG uptake has been thought to reflect differences in activity of “physiological” inflammation of the palatine tonsils. Increased glucose metabolism during active inflammation in the case of chronic tonsillitis or lymphocyte proliferation in the case of a patient that has received prior chemotherapy (likely experiencing compensatory extra medullar lymphoid hyperplasia) were thought to be causes of high FDG uptake in the tonsils. The significance of such increased tonsil FDG uptake is currently unknown however previous studies suggest that normal pharyngeal palatine tonsil uptake was generally symmetrical and that the difference in maximal standardized uptake value (SUVmax) between right and left tonsils (right-to-left ratio or a surrogate of symmetry) in the same patient might be helpful in detecting malignant tissue. The mean right-to-left ratio of tonsillar SUV was 4.55 in patients with confirmed malignant pathology and 1.53 in patients with documented benign tonsillar tissue (Table 4). The mean tonsillar SUVmax was 15.35 in patients with confirmed malignant pathology and 7.05 in patients with documented benign tonsillar tissue hence SUVmax seems to be useful in differentiating tumor from physiological accumulation. Younger patients with low SUV max symmetric tonsillar uptake and no other abnormal FDG areas seen during restaging PET could probably be watched non-invasively. Conclusions: At the time of initial staging PET, increased tonsil uptake showed true lymphomatous involvement in most cases. At restaging, increased tonsil uptake displayed no cases positive for lymphomatous involvement as all tonsillectomies and FNA biopsies were negative for malignancy. These findings seem to be valid irrespective of the subtype of lymphoma. Our study supports a conservative non-invasive approach because physiologic uptake is the most common cause of increased tonsil uptake when restaging lymphoma patients after treatment has been completed. Disclosures: No relevant conflicts of interest to declare.

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