Relevance of Positron Emission Tomography (PET) in Oncology

Background: The clinical use of positron emission tomography (PET) for detection and staging of malignant tumors is rapidly increasing. Furthermore, encouraging results for monitoring the effects of radio- and chemotherapy have been reported. Methods: This review describes the technical principles of PET and the biological characteristics of tracers used in oncological research and patient studies. The results of clinical studies published in peer reviewed journals during the last 5 years are summarized and clinical indications for PET scans in various tumor types are discussed. Results and Conclusions: Numerous studies have documented the high diagnostic accuracy of PET studies using the glucose analogue F-18-fluordeoxyglucose (FDG-PET) for detection and staging of malignant tumors. In this field, FDG-PET has been particularly successful in lung cancer, colorectal cancer, malignant lymphoma and melanoma. Furthermore, FDG-PET has often proven to be superior to morphological imaging techniques for differentiation of tumor recurrence from scar tissue. Due to the high glucose utilization of normal gray matter radiolabeled amino-acids like C-11-methionine are superior to FDG for detection and delineation of brain tumors by PET. In the future, more specific markers of tumor cell proliferation and gene expression may allow the application of PET not only for diagnostic imaging also but for non-invasive biological characterization of malignant tumors and early monitoring of therapeutic interventions. Hintergrund: Die Positronenemissionstomographie (PET) wird zunehmend in der Diagnostik onkologischer Erkrankungen eingesetzt. Auch in der Therapiekontrolle von Strahlen- und Chemotherapie maligner Tumoren wurde vielversprechende Ergebnisse berichtet. Methodik: Diese Übersicht beschreibt die technischen Grundlagen von PET-Untersuchungen und die biologischen Eigenschaften von Markern, die in der onkologischen Forschung und klinischen Diagnostik eingesetzt werden. Ergebnisse von in den letzten fünf Jahren in "peer-reviewed" Zeitschriften veröffentlichten klinischen Studien sind zusammengestellt, und klinische Indikationen für PET-Untersuchungen werden diskutiert. Ergebnisse und Schlußfolgerungen: In zahlreichen Studien wurde eine hohe diagnostische Genauigkeit der PET beim Nachweis und Staging maligner Tumoren unter Verwendung des Glucoseanalogons F-18-Fluordeoxyglucose (FDG) nachgewiesen. Die Anwendung der FDG-PET erwies sich als besonders erfolgreich bei Kopf-Hals-Tumoren, Bronchialkarzinomen, kolorektalen Karzinomen, malignen Melanomen und Lymphomen. Es wurde außerdem gezeigt, daß die FDG-PET bei der Differenzierung von Tumorrezidiven und therapiebedingten Veränderungen häufig der konventionellen bildgebenden Diagnostik überlegen ist. Bei der Diagnostik von Hirntumoren bieten radioaktiv markierte Aminosäuren wie C-11-Methionin aufgrund des hohen Glucosestoffwechsels der normalen grauen Stubstanz Vorteile gegenüber FDGT. Neue spezifische Marker für Tumorzellproliferation und Genexpression sind vielversprechende Ansätze für eine biologische Charakterisierung von Tumoren und Kontrolle von Therapieeffekten mittels PET.     

Relevance of Positron Emission Tomography (PET) in Oncology

BACKGROUND: The clinical use of positron emission tomography (PET) for detection and staging of malignant tumors is rapidly increasing. Furthermore, encouraging results for monitoring the effects of radio- and chemotherapy have been reported. METHODS: This review describes the technical principles of PET and the biological characteristics of tracers used in oncological research and patient studies. The results of clinical studies published in peer reviewed journals during the last 5 years are summarized and clinical indications for PET scans in various tumor types are discussed. RESULTS AND CONCLUSIONS: Numerous studies have documented the high diagnostic accuracy of PET studies using the glucose analogue F-18-fluordeoxyglucose (FDG-PET) for detection and staging of malignant tumors. In this field, FDG-PET has been particularly successful in lung cancer, colorectal cancer, malignant lymphoma and melanoma. Furthermore, FDG-PET has often proven to be superior to morphological imaging techniques for differentiation of tumor recurrence from scar tissue. Due to the high glucose utilization of normal gray matter radiolabeled amino-acids like C-11-methionine are superior to FDG for detection and delineation of brain tumors by PET. In the future, more specific markers of tumor cell proliferation and gene expression may allow the application of PET not only for diagnostic imaging also but for non-invasive biological characterization of malignant tumors and early monitoring of therapeutic interventions.     

Positron Emission Tomography (PET) and breast cancer in clinical practice

The landscape of oncologic practice has changed deeply during the past few years and there is now a need, through a multidisciplinary approach, for imaging to provide accurate evaluation of morphology and function and to guide treatment (Image Guided Therapy). Increasing emphasis has been put on Position Emission Tomography (PET) role in various cancers among clinicians [Juweid ME, Cheson BD. Positron-emission tomography and assessment of cancer therapy. N Engl J Med 2006;354:496-507; Koh DM, Cook GJR, Husband JE. New horizons in oncologic imaging. N Engl J Med 2003;348:25; Tafra L, positron emission tomography (PET) and mammography (PEM) for breast cancer: importance to surgeons. Ann Surg Oncol 2006;14(1):3-13] and patients despite a general context of healthcare expenditure limitation. Positron Emission Tomography has currently a limited role in breast cancer, but also general radiologists and specialists should be aware of these indications, especially when staging aggressive cancers and looking for recurrence. Currently, the hybrid systems associating PET and Computed Tomography (CT) and in the same device [Rohren EM, Turkington TG, Coleman RE. Clinical applications of PET in oncology. Radiology 2004;231:305-32; Blodgett TM, Meltzer CM, Townsend DW. PET/CT: form and function. Radiology 2007;242:360-85; von Schulthess GK, Steinert HC, Hany TF. Integrated PET/CT: current applications and futures directions. Radiology 2006;238(2):405-22], or PET-CT, are more commonly used and the two techniques are adding their potentialities. Other techniques, MRI in particular, may also compete with PET in some instance and as far as ionizing radiations dose limitation is considered, some breast cancers becoming some form of a chronic disease. Breast cancer is a very complex, non-uniform, disease and molecular imaging at large may contribute to a better knowledge and to new drugs development. Ongoing research, Positron Emission Mammography (PEM) and new tracers, are likely to bring improvements in patient care [Kelloff GJ, Hoffman JM, Johnson B, et al. Progress and promise of FDG-PET Imaging for cancer patient management and oncologic drug development. Clin Cancer Res 2005;1(April (8)): 2005].     

A Coordinate System for Tumor Identification in Positron Emission Tomography (PET) Imaging

Purpose: PET can be useful in determining the progression of malignant disease over time as well as the response to therapy. To achieve this, the physician must be able to unambiguously identify and characterize individual tumors among several different scans.Methods: We have developed a coordinate system for identifying individual tumor sites on PET scans, selecting the carina on the transmission scan as a point of origin. Using this system, each tumor is given a set of spherical coordinates that identifies its position: a rho (rho, displacement from carina), a theta (θ, angle between the A-P axis and the tumor), and a phi (φ, angle between the polar axis and the tumor). We tested this method on a patient with metastatic thyroid cancer, who underwent 18FDG and 124I-Iodide PET scans in the same week. This sytem was also used on a patient with metastatic prostate cancer, who had two FDG scans done 7 weeks apart. The patient underwent chemotherapy treatment during this period, and the scans were performed to assess therapy response.Results: The patient with thyroid cancer had a total of 90 tumors, 82 of them identified in the 18FDG scan and 35 in the 124I-Iodide scan, with 27 tumors identified in both. For rho, θ, and φ among the 27 matching pairs of tumors, the mean differences were 6.80 +/- 5 mm, 6.22 +/- 4.54 degrees, and 5.51 +/- 5.81 degrees, respectively. The disparity in coordinate values between corresponding tumors can be explained by the distinctive uptake patterns of the radiopharmaceuticals. The patient with prostate cancer had 9 tumors identifiable in both the pre- and post-therapy scans. The mean differences for rho, θ, and φ among the 9 pairs of tumors were 1.93 +/- 1.65 mm, 6.67 +/- 5.53 degrees, and 2.04 +/- 2.02 degrees, respectively. After thorough analysis, we have determined that corresponding tumors with rho < 15 mm, θ and φ < 15 degrees difference usually indicate a match.Conclusion: This coordinate system facilitates the identification and characterization of individual tumors among multiple scans, thus aiding in both the assessment of diagnostic capabilities of different tracers, and the tracking of tumors following therapy.     

8. A Spherical Coordinate System for Tumor Identification in Positron Emission Tomography (PET) Imaging

Purpose: PET can be useful in determining the progression of malignant disease over time as well as the response to therapy. To achieve this, the physician must be able to unambiguously identify and characterize individual tumors among several different scans.Methods: We have developed a spherical coordinate system for identifying individual tumor sites on PET scans, using the carina on the transmission scan as a point of origin. Using this system, each tumor is given a set of spherical coordinates that identifies its position: a rho (rho, displacement from carina), a theta (θ, angle between the A-P axis and the tumor), and a phi (φ, angle between the cranial-caudal axis and the tumor).Results: We tested this method on a patient with metastatic thyroid cancer, who underwent 18FDG and 124I-Iodide PET scans in the same week. The patient had a total of 90 tumors, 82 of them identified in the 18FDG scan and 35 in the 124I-Iodide scan, with 27 tumors identified in both. For rho, θ, and φ among the 27 matching pairs of tumors, the mean differences were 6.80 + 5 mm, 6.22 + 4.54 degrees, and 5.51 + 5.81 degrees, respectively. After thorough analysis, we have determined that corresponding tumors with rho < 15 mm, θ and φ < 15 degrees difference usually indicate a match. The disparity in coordinate values between corresponding tumors can be explained by the distinctive uptake patterns of the radiopharmaceuticals.Conclusion: Within a mean difference of 6.8 mm and 6 degrees, this spherical coordinate system facilitates the identification and characterization of individual tumors among multiple scans, thus aiding in both the assessment of diagnostic capabilities of different tracers, and the tracking of tumors following therapy.     

Quantitative Dosimetry for Yttrium-90 Radionuclide Therapy: Tumor Dose Predicts Fluorodeoxyglucose Positron Emission Tomography Response in Hepatic Metastatic Melanoma

PurposeTo assess a new method for generating patient-specific volumetric dose calculations and analyze the relationship between tumor dose and positron emission tomography (PET) response after radioembolization of hepatic melanoma metastases.Methods and MaterialsYttrium-90 (⁹⁰Y) bremsstrahlung single photon emission computed tomography (SPECT)/computed tomography (CT) acquired after ⁹⁰Y radioembolization was convolved with published ⁹⁰Y Monte Carlo estimated dose deposition kernels to create a three-dimensional dose distribution. Dose-volume histograms were calculated for tumor volumes manually defined from magnetic resonance imaging or PET/CT imaging. Tumor response was assessed by absolute reduction in maximum standardized uptake value (SUV_max) and total lesion glycolysis (TLG).ResultsSeven patients with 30 tumors treated with ⁹⁰Y for hepatic metastatic melanoma with available ⁹⁰Y SPECT/CT and PET/CT before and after treatment were identified for analysis. The median (range) for minimum, mean, and maximum dose per tumor volume was 16.9 Gy (5.7–43.5 Gy), 28.6 Gy (13.8–65.6 Gy) and 36.6 Gy (20–124 Gy), respectively. Response was assessed by fluorodeoxyglucose PET/CT at a median time after treatment of 2.8 months (range, 1.2–7.9 months). Mean tumor dose (P = .03) and the percentage of tumor volume receiving ≥ 50 Gy (P < .01) significantly predicted for decrease in tumor SUV_max, whereas maximum tumor dose predicted for decrease in tumor TLG (P < .01).ConclusionsVolumetric dose calculations showed a statistically significant association with metabolic tumor response. The significant dose-response relationship points to the clinical utility of patient-specific absorbed dose calculations for radionuclide therapy.     

8:45-90:00. The Influence of a High Fat Meal Compared to an Olestra Meal on Coronary Artery Endothelial Dysfunction by Rubidium (Rb)-82 Positron Emission Tomography (PET) and on Post Prandial Serum Triglycerides

Background: Cellular changes lead to coronary artery endothelial dysfunction (ED) and precede plaque formation. Clinical events, such as unstable angina and acute coronary syndromes, are common consequences of ED. Coronary artery ED, as characterized by Rb-82 PE, is a perfusion abnormality at rest, which improves following stress. In risk factor modification studies, particularly in cholesterol-lowering trials, coronary artery ED has been demonstrated to be reversible. Other studies have correlated low fat diet modification with improvement in coronary artery disease.Purpose: This study evaluates changes in myocardial perfusion following meals with low versus high TG content, and its influence on post prandial serum TG.Methods: With a randomized, double blind placebo controlled, cross over design, we investigated 19 patients (10 with ED and 9 with normal perfusion) with Rb-82 PET for myocardial blood flow at rest and with adenosine stress. PET images and serum triglycerides were obtained before and after an olestra (OA) meal (2.7g TG, 44g olestra) and a high-fat meal (46.7g TG). Meals were matched for carbohydrate, protein, and cholesterol content.Results: Myocardial perfusion (uCi/cc) increased 11 - 12% following the OA meal compared to the high-fat meal in patients with ED. For all patients combined, serum TG increased significantly (p < 0.01) in the non-OA group with the median change from baseline to 170.0 mg/dl, compared to 21.5 mg/dl in the OA group during the 6 hours following the meal.Conclusions: A single olestra meal significantly diminishes post prandial serum TG levels and improves myocardial perfusion in patients with endothelial disease.     

6. 18F-FDG Whole Body Positron Emission Tomography (PET) in the Detection of Unknown Primary Tumors

Purpose: To evaluate the utility of FDG-PET in detecting primary tumors in patients with metastatic disease from unknown primary tumors.Methods: 12 patients with metastases from unknown origin after unsuccessful conventional diagnostic procedures were studied. 5 had lymph node metastases (2 axillary, 2 cervical, 1 mediastinal), 3 multiple metastases, 1 in the lung, 1 in the cava vein, 1 in the brain and 1 in adrenal glands. Patients received 400MBq FDG intravenously, and whole body images were acquired 60 min. after injection with an ECAT EXACT HR+. PET results were compared with histological and clinical findings.Results: All but one metastatic lesion was identified by PET. Additional metastases were visualized in 4 patients. In one helped to guide biopsy for histological diagnosis. In 4/11 patients FDG-PET did not reveal lesions suspected to be primary tumor. FDG-PET identified primary tumor in 8/11 patients (breast: 2, pancreas: 2, base of tongue: 1, adrenal gland: 1, lung: 1, stomach: 1). In 4 of them (33% of total) primary tumor was confirmed either histologically or by the clinical evolution (breast: 2, lung: 1, pancreas: 1). In 1 patient FDG-PET was false positive (base of tongue). 3 patients positive FDG-PET have not yet been confirmed. FDG-PET influenced therapeutic procedures in 4 patients (33% of total). 2 underwent surgery (breast), 1 received specific chemotherapy (lung) and 1 palliative chemotherapy (pancreas).Conclusions: Our preliminary results suggest that FDG-PET is a non-invasive technique useful in the detection of unknown primary tumors, can influence in selecting appropriate therapeutic management and could guide biopsies for histologic analysis.     

Clinical Relevance of Positron Emission Tomography (PET) in Treatment Control and Relapse of Hodgkin's Disease

BACKGROUND: In Hodgkin's disease accurate restaging is important to assess treatment results and may eventually provide a basis for further therapeutic strategies. A typical dilemma after treatment of Hodgkin's disease with radiographically persistent lymphoma is the differentiation between sterilized residual mass and viable tumor. Positron emission tomography (PET) has been described as a reliable tool to identify active lymphoma. Aim of the present study was to assess the accuracy and clinical relevance of PET for treatment control and in the situation of a suspected relapse of Hodgkin's disease. PATIENTS AND METHODS: 63 patients (32 men, 31 women, mean age 41.5 years) with Hodgkin's disease were investigated with FDG-PET. In 51 patients 63 PET studies were performed as a treatment control (group 1) after primary therapy. 17 patients (5 of whom preexamined in group 1) underwent 18 PET scans for confirmation of suspected relapse (group 2). PET was performed with a dedicated whole-body ring scanner. In a retrospective analysis, all FDG-PET scans were compared with conventional imaging methods and related to the final diagnosis obtained by histology and/or clinical follow-up (mean 22.4 months). RESULTS: Group 1: FDG-PET showed an accuracy of 91%, whereas the accuracy of conventional imaging was 62%. Group 2: The accuracy for PET was 83% and 56% for conventional imaging. CONCLUSION: The present data suggest that PET is a sensitive and reliable tool for detection of involved areas of active Hodgkin's disease. The accuracy of PET for restaging purpose seems to be superior than conventional imaging.     

Clinical Relevance of Positron Emission Tomography (PET) in Treatment Control and Relapse of Hodgkin's Disease

Background: In Hodgkin's disease accurate restaging is important to assess treatment results and may eventually provide a basis for further therapeutic strategies. A typical dilemma after treatment of Hodgkin's disease with radiographically persistent lymphoma is the differentiation between sterilized residual mass and viable tumor. Positron emission tomography (PET) has been described as a reliable tool to identify active lymphoma. Aim of the present study was to assess the accuracy and clinical relevance of PET for treatment control and in the situation of a suspected relapse of Hodgkin's disease. Patients and Methods: 63 patients (32 men, 31 women, mean age 41.5 years) with Hodgkin's disease were investigated with FDG-PET. In 51 Patients 63 PET studies were performed as a treatment control (group 1) after primary therapy. 17 patients (5 of whom preexamined in group 1) underwent 18 PET scans for confirmation of suspected relapse (group 2). PET was performed with a dedicated whole-body ring scanner. In a retrospective analysis, all FDG-PET scans were compared with conventional imaging methods and related to the final diagnosis obtained by histology and/or clinical follow-up (mean 22.4 months). Results: Group 1: FDG-PET showed an accuracy of 91%, whereas the accuracy of conventional imaging was 62%. Group 2: The accuracy for PET was 83% and 56% for conventional imaging. Conclusion: The present data suggest that PET is a sensitive and reliable tool for detection of involved areas of active Hodgkin's disease. The accuracy of PET for restaging purpose seems to be superior than conventional imaging. Hintergrund: Ein akkurates Restaging ist nach Primärtherapie ein Morbus Hodgkin von besonserer Bedeutung für die Einschätzung des Therapieerfolgs und eventuelle Festlegung weiterer Behandlungsmaßnahmen. Häufig besteht das Problem, bei röntgenmorphologisch fortbestehender Raumforderung zwischen sterilisiertem Resttumor und aktivem Lymphom zu unterscheiden. Für diese Situation wird die Positronenemissionstomographie (PET) als zuverlässige Methode zur Detektion aktiver Lymphommanifestationen beschrieben. Ziel der vorliegenden Studie war es, Zuverlässigkeit (accuracy) und klinische Relevanz von PET in der Therapiekontrolle und bei Verdacht auf Rezidiv zu evaluieren. Patienten und Methode: Insgesamt wurden 63 Patienten (32 Männer, 31 Frauen, Durchschnittsalter 41,5 Jahre) untersucht. Bei 51 Patienten wurden 63 PET-Scans nach Primärbehandlung zur Therapiekontrolle (Gruppe 1) durchgeführt, bei 17 Patienten (davon fünf in Gruppe 1 voruntersucht) erfolgten 18 PET-Untersuchungen zur Abklärung bei Verdacht auf Rezidiv. Die PET wurde mit einem Ganzkörper-Vollring-Scanner durchgeführt. Alle PET-Befunde wurden in einer retrospektiven Analyse mit denen radiologischer bzw. kernspintomographischer Untersuchungen verglichen und mit der endgültigen Diagnose auf der Basis histologischer Befunde und/oder des klinischen Verlaufs korreliert. Resultate: Gruppe 1: Die Zuverlässigkeit von FDG-PET lag bei 91%, die der herkönnlichen Bildgebung (CT, MR) bei 62%. Gruppe 2: Hier zeigte PET eine Zuverlässigkeit von 83% im Gegensatz zu herkömmlichen bildgebenden Verfahren mit 56%. Schlussfolgerung: PET erscheint anhand der vorgestellten Daten als empfindliche und zuverlässige Methode zur Darstellung von aktiven Lymphommanifestationen. Die Zuverlässigkeit von PET im Restaging des Morbus Hodgkin zeigte sich der der herkömmlichen Bildgebung als üerlegen.     

Semi-Quantitative Analysis of Post-Transarterial Radioembolization 90Y Microsphere Positron Emission Tomography Combined with Computed Tomography (PET/CT) Images in Advanced Liver Malignancy: Comparison With 99mTc Macroaggregated Albumin (MAA) Single Photon Emission Computed Tomography (SPECT)

Objectives

The purpose of this study is to evaluate the correlation between pretreatment planning technetium-99m (^99mTc) macroaggregated albumin (MAA) SPECT images and posttreatment transarterial radioembolization (TARE) yttirum-90 (⁹⁰Y) PET/CT images by comparing the ratios of tumor-to-normal liver counts.

Methods

Fifty-two patients with advanced hepatic malignancy who underwent ⁹⁰Y microsphere radioembolization from January 2010 to December 2012 were retrospectively reviewed. Patients had undergone ^99mTc MAA intraarterial injection SPECT for a pretreatment evaluation of microsphere distribution and therapy planning. After the administration of ⁹⁰Y microspheres, the patients underwent posttreatment ⁹⁰Y PET/CT within 24 h. For semiquantitative analysis, the tumor-to-normal uptake ratios in ⁹⁰Y PET/CT (TNR-yp) and ^99mTc MAA SPECT (TNR-ms) as well as the tumor volumes measured in angiographic CT were obtained and analyzed. The relationship of TNR-yp and TNR-ms was evaluated by Spearman''s rank correlation and Wilcoxon''s matched pairs test.

Results

In a total of 79 lesions of 52 patients, the distribution of microspheres was well demonstrated in both the SPECT and PET/CT images. A good correlation was observed of between TNR-ms and TNR-yp (rho value = 0.648, p < 0.001). The TNR-yp (median 2.78, interquartile range 2.43) tend to show significantly higher values than TNR-ms (median 2.49, interquartile range of 1.55) (p = 0.012). The TNR-yp showed weak correlation with tumor volume (rho = 0.230, p = 0.041).

Conclusions

The ^99mTc MAA SPECT showed a good correlation with ⁹⁰Y PET/CT in TNR values, suggesting that ^99mTc MAA can be used as an adequate pretreatment evaluation method. However, the ^99mTc MAA SPECT image consistently shows lower TNR values compared to ⁹⁰Y PET/CT, which means the possibility of underestimation of tumorous uptake in the partition dosimetry model using ^99mTc MAA SPECT. Considering that ^99mTc MAA is the only clinically available surrogate marker for distribution of microsphere, we recommend measurement of tumorous uptake using ⁹⁰Y PET/CT should be included routinely in the posttherapeutic evaluation.     

Positron Emission Tomography (PET) with 1-Aminocyclobutane-1-[(11)C]carboxylic Acid (1-[(11)C]-ACBC) for Detecting Recurrent Brain Tumors

This study was done to determine whether 1-[(11)C]ACBC PET has any advantages over 2-[(18)F]FDG PET, CT, or MRI in detecting recurrent brain tumors, and whether quantitative 1-[(11)C]ACBC PET information improves the accuracy of "visual" image interpretation.Twenty patients with recurrent brain tumor underwent dynamic PET. Images were analyzed by visual interpretation; in addition, standardized uptake values (SUVs) and Patlak values (k(1)*k(3)/k) were evaluated.1-[(11)C]ACBC identified 19/20 recurrent brain tumors, [18F]FDG 13/19, MRI 13/19, and CT 8/16. Based on SUVs, the average tumor-to-contralateral gray matter ratio of 1-[(11)C]ACBC was 5.0 and 0.5 for 2-[(18)F]FDG. Mean Patlak values of 1-[(11)C]ACBC were 0.044 +/- 0.047 for high and 0.034 +/- 0.026 for low grade tumors. However, visual interpretation was effective without quantitative PET data.1-[(11)C]ACBC, accurately detects recurrent tumors for selecting biopsy sites and treatment planning.     

Identification of transport processes in bioirrigated muddy sediments by [18F]fluoride PET (Positron Emission Tomography)

In aquatic environments transport processes across the sediment–water interface are intensified by bioirrigating macrozoobenthos. Transport processes caused by Chironomus plumosus larvae dwelling in U-tubes were investigated by dynamic small animal Positron Emission Tomography (PET) with [18F]fluoride. Significant tracer transport from the burrows into the sediment was detected; penetration was deeper at the outlet branch of the burrow than at the inlet branch. Hence, advection plays a significant role in exchange between water in the burrows and muddy sediment.     

9:30-9:45. Preliminary Evaluation of F-18 Fluorocholine (FCH) as a PET Tumor Imaging Agent

The purpose of this study was to develop and evaluate an F-18 labeled choline tumor imaging agent.FCH was synthesized through the intermediate F-18 fluorobromomethane that was used to alkylate dimethylethanolamine. The isolated FCH was evaluated in PC-3 human prostate cancer cells, PC-3 human prostate cancer xenograft studies, and human prostate and brain tumor patients.FCH was accumulated at a slightly lower rate than FDG in the cultures of PC-3 cells. Inhibition of choline transport and phosphorylation by hemicholinium-3 resulted in a 90% decrease in FCH uptake without altering FDG uptake. FCH had a similar biodistribution as C-14 choline in mice, with the liver and kidneys being the primary sites of uptake. Tumor uptake of FCH and FDG were comparable at 45-60 mins after injections. The tumor:blood ratio was higher for FCH (5.3 +/- 2.4) than for FDG (3.2 +/- 0.3). Brain uptake of FCH was 10% that of FDG. FCH-PET studies were compared to FDG-PET studies. In the prostate cancer patients, more lesions have been seen on the FCH studies than on the FDG studies, and the standardized uptake values (SUV) have been higher with the FCH. Decreases in FCH-PET SUV have been noted in patients treated by androgen deprivation. Patients with suspected recurrent brain tumors have had more clearly defined abnormal accumulation on the FCH-PET scans than on the FDG-PET scans. The FCH is not accumulated by normal cortex.FCH is a promising imaging agent for the evaluation of metastatic prostate cancer and recurrent brain tumor.     

10. Positron Emission Tomography in the Presurgical Evaluation of Patients with Resectable Liver Metastases from Colorectal Carcinoma Detected by Computed Tomography with Arterial Portography. A Cost Analysis

Purpose: To assess the cost of implementing 18F-Fluorodeoxyglucose (18FDG) PET scan in the presurgical evaluation of patients with hepatic metastases from colorectal cancer (CRC) detected by Computed Tomography with arterial portography (CTAP).Methods: We performed a cost analysis of two diagnostic pathways based on a population of CRC patients with metastatic disease limited to the liver by (CTAP). The payers' perspective was utilized. The algorithms compared 18FDG-PET with Computed Tomography (CT) versus CT alone. Patients found to have extrahepatic disease by 18FDG-PET or CT were assigned to palliative care. Patients found to be negative for extrahepatic extension were assumed to be surgically resectable. The prevalence of extrahepatic disease, true and false positives and negatives for CT and 18FDG-PET were extracted from published reports (Medline, 1991 to 1999). Three possible outcomes for surgery were considered: uncomplicated, complicated, and death. Surgical complications considered were: urinary tract infection, wound sepsis, intra-abdominal abscess, septicemia, pneumonia, deep venous thrombosis, pulmonary embolism, anemia requiring transfusion, and myocardial infarction. Complication rates, costs for CT, CTAP, 18FDG-PET, surgery and post-surgical complications were obtained from HCFA published data (1997-2000). Palliative care costs were assumed to be identical in both branches.Results: Average expected cost per patient with 18FDG-PET was $16,921, compared to $21,693 for a patient without PET scan. This represents net savings of $4,772 if PET is included in the diagnostic work up.Conclusion: Integration of 18FDG-PET in the presurgical evaluation of patients with liver metastases from CRC by CTP would substantially reduce overall costs.