PET and [18F]-FDG in oncology: a clinical update

Clinical applications of FDG-PET in oncology

Positron emission tomography together with F-18-deoxyglucose (FDG) has emerged as a valuable clinical tool in the field of oncology. FDG-PET diagnoses, stages and restages most cancers with a high diagnostic accuracy. The effects of chemotherapy on tumour metabolism can be monitored with this whole-body technique. Recent studies have established a high prognostic accuracy of PET for predicting the clinical outcome of cancer patients. The current review addresses the role of FDG-PET for diagnosing, staging and restaging of lung cancer, colorectal cancer, lymphoma, melanoma and breast cancer staging and provides a brief outlook for future applications of clinical PET imaging.

Positron emission tomography affects surgical management in recurrent colorectal cancer patients

BACKGROUND

We determined the effect of positron emission tomography (PET) on surgical decision-making in patients with metastatic or recurrent colorectal cancer.

METHODS

A total of 114 patients with advanced colorectal cancer were imaged with computed tomography (CT) and PET scans. The PET and CT scans were independently interpreted before surgery and recorded.

RESULTS

Forty-two of the 114 patients had resectable disease on the basis of CT. PET altered therapy in 17 (40%) of these 42 patients on the basis of the following results: extrahepatic disease (n = 9), bilobar involvement (n = 3), thoracic involvement (n = 5), retroperitoneal lymphadenopathy (n = 2), bone involvement (n = 1), and supraclavicular disease (n = 1). In 25 patients with liver metastases only, PET found additional disease in 18 (72%), extrahepatic disease in 11, chest disease in 13, retroperitoneal lymphadenopathy in 4, and bone disease in 3. In five patients, both scans underestimated small-volume peritoneal metastases discovered at laparotomy.

CONCLUSIONS

PET altered therapy in 40% of patients. In patients with isolated liver involvement, 72% had more extensive disease that precluded surgical resection. PET scans should be used in the management of patients with recurrent colorectal cancer who are being considered for potentially curative surgery.

Physiologic FDG-PET three-dimensional brachytherapy treatment planning for cervical cancer

PURPOSE

To compare conventional two-dimensional (2D) orthogonal radiography-based brachytherapy treatment planning for cervical cancer with a three-dimensional (3D) treatment planning technique based on 18F-fluoro-deoxyglucose-positron emission tomography (FDG-PET).

METHODS AND MATERIALS

Eleven cervical cancer patients were included in this prospective study that evaluated one tandem and ovoid brachytherapy procedure for each patient. The patient underwent FDG-PET of the pelvis to visualize the tumor followed by a second FDG-PET scan with the FDG isotope placed inside the tandem and ovoid applicators to visualize the treatment source positions for 3D treatment planning. The tumor volumes were delineated using a binary threshold technique in which the threshold FDG-PET image intensity was 40% of the peak tumor intensity.

RESULTS

FDG-PET provides a reliable estimate of the cervical cancer volume and 3D spatial relationship of the tumor to the tandem and ovoid applicators. The maximal bladder and rectal doses determined from the 3D FDG-PET dose-volume histograms were found to be higher than those obtained using 2D treatment planning. The minimal dose to the tumor volume defined by FDG-PET ranged from 50 to 475 cGy for treatment plans designed to deliver 650 cGy to Point A and exhibited an inverse correlation with tumor volume.

CONCLUSION

Physiologic FDG-PET brachytherapy treatment planning is feasible and accurate relative to conventional 2D treatment planning. The use of FDG-PET offers a unique method for tumor visualization and identifies the limitations of conventional brachytherapy treatment planning for coverage of large tumors and estimation of the dose to normal structures. This technique has the potential for improving isodose tumor coverage for patients with cervical cancer while sparing critical structures.

Positron emission tomography in prostate and renal cell carcinoma

PURPOSE OF REVIEW

The present review addresses technical improvements in [18F]deoxyglucose positron emission tomography (PET) and new tracer developments that may increase detection in prostate cancer and renal cell carcinoma. In addition, we discuss the future of molecular imaging in prostate cancer.

RECENT FINDINGS

PET has proven useful in imaging primary and metastatic cancer in a variety of tumor types. Previous work suggested that the most common radiopharmaceutical used in PET imaging - [18F]deoxyglucose - has a limited role in diagnosing primary prostate cancer and renal cell carcinoma. Technical improvements in scanning techniques and in PET scanners have increased detection of primary and metastatic lesions in both tumor types with [18F]deoxyglucose PET, as compared with previous studies. These improvements include increased scanner resolution and improved processing algorithms. In both prostate and renal cell carcinoma, however, better detection may result from the development of new tracers, particularly those that are not excreted into renal collecting systems. Labeled choline shows promise, as does [11C]acetate. New tracers for prostate cancer could be developed to detect changes that signal malignant transformation, as well as tracers that could show expression of genes administered for therapy.

SUMMARY

Technical improvements and the development of new tracers will probably make PET imaging a viable diagnostic tool in prostate cancer and renal cell carcinoma.

Incidental detection of colon cancer by FDG positron emission tomography in patients examined for pulmonary nodules

PURPOSE

Fluorodeoxyglucose (FDG) positron emission tomographic (PET) imaging has been used extensively to diagnose cancer with high rates of sensitivity and specificity. One of its applications is to distinguish benign from malignant pulmonary nodules. It is common to observe colonic uptake on whole-body FDG-PET images. Because patients with lung cancer also tend to be in the age group with the highest incidence of colon cancer, the authors tried to assess the efficacy of FDG-PET for detecting occult colon cancer in patients referred for the evaluation of lung nodules.

METHODS

The records of 500 consecutive patients referred for the evaluation of pulmonary nodules were reviewed retrospectively. Among the patients, 197 had no previous clinical or radiographic evidence of abnormalities in the gastrointestinal tract, and none had been found to have any cancer before undergoing an FDG-PET study. All colon lesions were verified either by histologic analysis or by clinical course.

RESULTS

Among the 197 patients analyzed, 59 had diffuse colonic uptake in various segments of the colon. Seventeen of the patients had focal colonic uptake, five of which were proved to be colon cancer.

CONCLUSIONS

The routine use of FDG PET to characterize lung lesions significantly increases the probability of detecting unexpected extrathoracic disease. In these patients, the incidental finding of colon cancer had an important effect on their treatment and may prove to be very cost-effective.

Incidental colonic fluorodeoxyglucose uptake: correlation with colonoscopic and histopathologic findings

PURPOSE

To evaluate the pattern and degree of incidental colonic fluorodeoxyglucose (FDG) uptake in patients without colorectal carcinoma who underwent whole-body FDG positron emission tomography (PET) for other purposes and compare them with colonoscopic and/or histopathologic findings.

MATERIALS AND METHODS

Cases of 27 patients without known history of colorectal carcinoma who were referred for evaluation with whole-body FDG PET and displayed incidental colonic uptake were reviewed retrospectively. Colonoscopy was performed in 10 patients; histopathologic analysis, in two; and both, in 15. The colonic FDG uptake patterns were nodular-focal, nodular-multifocal, segmental, and diffuse. The FDG uptake level was scored with a four-point scale in relation to hepatic uptake. Binomial distribution was used to calculate 95% CIs for the probability of finding an abnormality at histologic examination, as predicted by findings at FDG PET.

RESULTS

Colonoscopic findings in eight patients with a diffuse uptake pattern were normal. Thirteen patients with nodular high FDG uptake had pathologic findings. Six (22%) of the 27 patients were not suspected of having a malignancy, and seven had benign neoplasms. With a 95% CI, nodular high FDG uptake implies at least a 79% chance that histopathologic findings may be abnormal. Colitis was seen in five of six patients with a segmental pattern of high FDG uptake.

CONCLUSION

Colonoscopy is a reasonable next step for further diagnostic examination of patients who display nodular high FDG uptake in the colon. Diffuse FDG uptake often is associated with normal findings at colonoscopy, while segmental high uptake may imply inflammation.

Ferumoxide-enhanced magnetic resonance imaging techniques in pre-operative assessment for colorectal liver metastases

AIM

The objective was to evaluate whether contrast-enhanced magnetic resonance imaging (MRI) techniques used in a pre-operative assessment protocol for colorectal liver metastases are as accurate as spiral computer tomography during arterial portography (CTAP). Pre-operative accuracy and clinical consequences of MRI are described and compared with CTAP. Moreover, post-operative survival rate and tumour recurrence were studied.

METHODS

The study group comprised 84 patients which were possible candidates for a partial hepatectomy for colorectal liver metastases. Patients were pre-operatively evaluated by CT of the abdomen, CT of the thorax and spiral CTAP and ferumoxide-enhanced MRI was performed in routine way for all patients. Following this selection, 35 patients underwent a partial hepatectomy with curative intent. All patients were retrospectively evaluated.

RESULTS

Ferumoxide-enhanced MRI proved to be at least as accurate as spiral CTAP in 81% of patients. In nine patients (11%) spiral CTAP revealed more intrahepatic lesions than MRI; in only two patients (2%) did these foundings influenced the clinical decision. These patients were considered to have irresectable disease. In seven patients (8%) MRI detected more lesions than spiral CTAP and influenced the clinical decision in three patients (4%) and these did not undergo a laparotomy. The actuarial 3 year overall survival of operated patients was 41% and the actuarial 3 year disease-free survival was 19%.

CONCLUSION

Evaluation of the clinical impact of a pre-operative assessment protocol extended with ferumoxide MRI techniques demonstrated that this non-invasive MRI technique is safe and at least as accurate as spiral CTAP. This MRI technique results in comparable clinical decisions and outcome after hepatectomy. We suggest that the performance of routine contrast-enhanced MRI should instead be used in the pre-operative evaluation of colorectal liver metastases.

Monitoring the correction of glycogen storage disease type 1a in a mouse model using [(18)F]FDG and a dedicated animal scanner

Monitoring gene therapy of glycogen storage disease type 1a in a mouse model was achieved using [(18)F]FDG and a dedicated animal scanner. The G6Pase knockout (KO) mice were compared to the same mice after infusion with a recombinant adenovirus containing the murine G6Pase gene (Ad-mG6Pase). Serial images of the same mouse before and after therapy were obtained and compared with wild-type (WT) mice of the same strain to determine the uptake and retention of [(18)F]FDG in the liver. Image data were acquired from heart, blood pool and liver for twenty minutes after injection of [(18)F]FDG. The retention of [(18)F]FDG was lower for the WT mice compared to the KO mice. The mice treated with adenovirus-mediated gene therapy had retention similar to that found in age-matched WT mice. These studies show that FDG can be used to monitor the G6Pase concentration in liver of WT mice as compared to G6Pase KO mice. In these mice, gene therapy returned the liver function to that found in age matched WT controls as measured by the FDG kinetics in the liver compared to that found in age matched wild type controls.

Endometrial carcinoma diagnosed by positron emission tomography: a case report

BACKGROUND

Positron emission tomography (PET) scanning utilizes the recognized tumor metabolic property of increased glycolysis with the radioactive decay of 2-[(18)F]fluoro-2-deoxy-D-glucose (FDG) and generation of gamma radiation to provide quantitative tumor imaging. PET scanning has proven useful in the evaluation and staging of malignancies including malignant melanoma.

CASE REPORT

As part of the preoperative staging evaluation a PET scan was performed in a 76-year-old white female with a biopsy-proven malignant melanoma on the posterior thorax. Physiologic uptake was delineated, and in addition, an area of increased uptake of FDG in the pelvis anatomically consistent with the uterus was observed. Subsequent endometrial sampling revealed a moderately differentiated endometrioid adenocarcinoma. Surgical staging revealed a stage IB, grade 2 lesion.

CONCLUSION

This is the first case report of an endometrial carcinoma diagnosed incidentally by positron emission tomography in an asymptomatic patient.

Evaluation of 18 F-fluorodeoxyglucose positron emission tomography and computed tomography with histopathologic correlation in the initial staging of head and neck cancer

OBJECTIVE

To prospectively evaluate the use of 18F-Fluorodeoxyglucose positron emission tomography (FDG-PET) in the initial staging of squamous cell head and neck carcinoma.

SUMMARY BACKGROUND DATA

The status of cervical lymph nodes is an important prognostic factor and determinant of management approach in squamous cell head and neck cancer.

METHODS

FDG-PET findings were compared with those of computed tomography (CT) before removal of the primary tumor and/or neck dissection. Histopathologic analysis was used as the gold standard for assessment of the sensitivity and specificity of these modalities.

RESULTS

FDG-PET correctly identified the primary tumor in 35 of 40 patients in whom the site of the primary was known clinically and still present (sensitivity 88%). None of four unknown primaries were detected. Tumors not detected by FDG-PET were generally superficial, with depths of less than 4 mm. CT correctly identified 18 of the 35 primary tumors (sensitivity 51%). Eleven of 17 CT false-negative tumors were detected by FDG-PET. The sensitivity and specificity for the presence of metastatic neck disease on FDG-PET were 82% and 100%, respectively; those for CT were 81% and 81%, respectively. FDG-PET was true positive for metastatic neck disease in two of the three CT false-negative patients.

CONCLUSIONS

FDG-PET shows promise in the initial staging of head and neck cancer and provides additional accuracy to a conventional staging process using CT.

Measurement of tumor volume by PET to evaluate prognosis in patients with advanced cervical cancer treated by radiation therapy

PURPOSE

This study evaluated the usefulness of tumor volume measurement with positron emission tomography (PET) in patients with advanced cervical cancer treated by radiation therapy.

METHODS AND MATERIALS

Fifty-one patients underwent PET before treatment. Primary tumor volume was determined, and volume, FIGO stage, and presence of lymph nodes on the PET study were compared to progression-free survival (PFS) and overall survival (OS).

RESULTS

Tumor volume, lymph node disease, and stage were predictive of PFS, whereas volume and lymph node involvement predicted OS. Lymph node status did not correlate with volume. Dividing patients according to whether the tumor volume was more or less than 60 cm(3) predicted PFS and OS. Separation of patients with tumor volumes <or=60 cm(3) and no lymph node disease vs. any other combination was strongly predictive of PFS and OS.

CONCLUSIONS

The following conclusions were drawn regarding patients with advanced cervical cancer treated with radiation therapy: (1) Tumor volume can be accurately measured by PET; (2) Tumor volume separates patients with a good prognosis from those with a poorer prognosis; (3) A subset of patients with relatively small tumors and no lymph node involvement does remarkably well; (4) Tumor volume does not correlate with the presence of lymph node disease.

Current status of positron emission tomography in oncology

Positron emission tomography (PET) has emerged as a powerful diagnostic tool in oncology patients. There is evidence of the superior utility over conventional imaging methods of the principal PET tracer 18F-fluoro-2-deoxy-glucose in the staging of a range of cancers and monitoring disease recurrence, as well as changing patient management to more appropriate therapy. The methods for evaluating the evidence for PET remain complex, particularly as the standard evidence-based approach of randomized controlled trials is not generally applicable to imaging technologies. PET has the potential to dramatically improve our ability to manage patients with cancer and is also making major contributions to the development of new therapies.

Synthesis of syn- and anti-1-amino-3-[18F]fluoromethyl-cyclobutane-1-carboxylic acid (FMACBC), potential PET ligands for tumor detection

syn- and anti-1-amino-3-[18F]fluoromethyl-cyclobutane-1-carboxylic acid (FMACBC, 16 and 17), analogues of anti-1-amino-3-[18F]fluorocyclobutyl-1-carboxylic acid (FACBC), were prepared to evaluate the contributions of C-3 substitution and configuration on the uptake of these radiolabeled amino acids in a rodent model of brain tumors. Radiofluorinated targets [18F]16 and [18F]17 were prepared by no-carrier-added radiofluorination from their corresponding methanesulfonyl esters 12 and 13, respectively, with decay-corrected radiochemical yields of 30% for [18F]16 and 20% for [18F]17. In amino acid transport assays performed in vitro using 9L gliosarcoma cells, both [18F]16 and [18F]17 were substrates for L type amino acid transport, while [18F]17 but not [18F]16 was a substrate for A type transport. Biodistribution studies in normal Fischer rats with [18F]16 and [18F]17 showed high uptake of radioactivity (>2.0% dose/g) in the pancreas while other tissues studied, including liver, heart, lung, kidney, blood, muscle, and testis, showed relatively low uptake of radioactivity (<1.0% dose/g). In rats implanted intracranially with 9L gliosarcoma cells, the retention of radioactivity in tumor tissue was high at 5, 60, and 120 min after intravenous injection of [18F]16 and [18F]17 while the uptake of radioactivity in brain tissue contralateral to the tumor remained low (<0.3% dose/g). Ratios of tumor uptake to normal brain uptake for [18F]16 were 7.5:1, 7:1, and 5:1 at 5, 60, and 120 min, respectively, while for [18F]17 the ratios were 7.5:1, 9:1, and 9:1 at the same time points. This work demonstrates that like anti-[18F]FACBC, [18F]16 and [18F]17 are excellent candidates for imaging brain tumors.

T1 lung cancers: sensitivity of diagnosis with fluorodeoxyglucose PET

PURPOSE

To determine the sensitivity of fluorodeoxyglucose (FDG) positron emission tomography (PET) in patients with T1 (< or =3 cm) lung cancers.

MATERIALS AND METHODS

One hundred eighty-five patients with 192 histopathologically proved T1 lung cancers underwent FDG PET imaging at the time of diagnosis. PET results were correlated with tumor size, histopathologic findings, and patient outcome by using the two-sample t test, exact chi(2) test, and log rank test, respectively.

RESULTS

Of the 192 lesions, 183 (95%) that ranged in size from 0.5 to 3.0 cm in diameter (mean, 2.0 cm) were positive at PET (ie, demonstrated increased FDG uptake). Of the 192 lesions, nine (5%) that ranged in size from 0.3 to 2.5 cm in diameter (mean, 1.3 cm) were negative at PET (ie, demonstrated low FDG uptake). Patients with small tumors, as well as those with carcinoid tumors and bronchioloalveolar cell carcinoma, were more likely to have a negative PET scan (P =.004, P =.003, respectively). In addition, patients with a negative PET scan who subsequently proved to have cancer had significantly longer survival than did patients with a positive scan and cancer (P =.043).

CONCLUSION

Most T1 lung cancers show increased FDG uptake on PET scans.

Positron emission tomography scanning: current and future applications

Whole-body positron emission tomography (PET) imaging with (18)F deoxyglucose (FDG) is a molecular imaging modality that detects metabolic alterations in tumor cells that are common to neoplastic cells. FDG-PET has recently been approved by the Health Care Finance Administration for Medicare reimbursement for diagnosing, staging, and restaging lung cancer, colorectal cancer, lymphoma, melanoma, head and neck cancer, and esophageal cancer. This review discusses the scientific evidence that led to the emergence of PET imaging as an accepted clinical tool in patients with solitary pulmonary nodules, lung cancer, colorectal cancer, melanoma, lymphoma, breast cancer, and other cancers. When possible, we compare the performance of PET to that of anatomical imaging. We discuss future clinical applications of this imaging modality.

Positron emission tomography in colorectal cancer

Positron emission tomography (PET) using (18)F-fluorodeoxyglucose (FDG) is increasingly used in the diagnostic management of colorectal cancer patients. It provides a highly sensitive and specific diagnosis which is entirely based upon alterations of the glucose metabolism found in malignant tissues. The information provided by FDG-PET is independent of the underlying structural characteristics of the lesions and, therefore, it is essentially complementary to the available structural imaging modalities such as CT, MRI and (endoscopic) ultrasound. Several studies have now been performed on the use of FDG-PET in colorectal adenocarcinoma for primary pre-operative staging, for diagnosis and (re)staging of recurrent disease, for localization and staging of occult recurrent disease, and for the assessment of the metabolic effects of chemotherapy and radiotherapy. This chapter aims to clarify some fundamental issues of both detection device and radiotracer, the proven indications for FDG-PET, the strength and limitations of the technique, and how its implementation would affect patient management.

[Basic principles of 18F-fluorodeoxyglucose positron emission tomography]

Positron emission tomography uses photons to receive regional information about dynamic, physiologic, and biochemical processes in the living body. A positron decay is measured indirectly by the simultaneous registration of both gamma rays created by the annihilation. The event is counted, if two directly opposite located detectors register gamma rays in coincidence. Unfortunately the detectors of a positron emission tomography system do not register only true coincident events. There are also scattered and random coincidences. Different types of positron tomographs are presented and scintillation crystals, which are in use for positron emission tomography are discussed. The 2D- and 3D-acquisition methods are described as well as preprocessing methods, such as correction for attenuation, scatter and dead time. For quantification the relative parameter standard uptake value (SUV) is explained. Finally hybrid systems, such as combined positron emission tomography/computed tomography scanners and the use of computed tomography data for attenuation correction are introduced.

A prospective study of 2-[18F] fluoro-2-deoxy-D-glucose/positron emission tomography scan, 99mTc-labeled arcitumomab (CEA-scan), and blind second-look laparotomy for detecting colon cancer recurrence in patients with increasing carcinoembryonic antigen levels

BACKGROUND

An increasing carcinoembryonic antigen (CEA) level in the absence of disease on imaging studies can present a diagnostic challenge. We evaluated 2-[18F] fluoro-2-deoxy-D-glucose and positron emission tomography (FDG-PET) scan and CEA scan before second-look laparotomy as a means of localizing recurrent colorectal cancer.

METHODS

Patients underwent computed tomography scan, bone scan, colonoscopy, and magnetic resonance imaging, and those without evidence of disease or resectable disease in the abdomen had FDG-PET and CEA scans. At second-look laparotomy, a surgeon blinded to the results of the FDG-PET and CEA scans performed an exploration and mapped findings. A second surgeon, with knowledge of the FDG-PET and CEA scans, then explored the patient; all lesions were biopsied or resected for pathology.

RESULTS

In 28 patients explored, disease was found at operation in 26 (94%). Ten had unresectable disease. FDG-PET scans predicted unresectable disease in 90% of patients. CEA scans failed to predict unresectable disease in any patient. In 16 patients found to have resectable disease or disease that could be treated with regional therapy, FDG-PET scan predicted this in 81% and CEA scan in 13%.

CONCLUSIONS

FDG-PET scan can predict those patients who would likely benefit from a laparotomy. If the FDG-PET scan indicates resectable disease, laparotomy can be considered. However, if the findings predict unresectable disease or the absence of disease, the patient should pursue systemic therapy or continued observation.

From tumor biology to clinical Pet: a review of positron emission tomography (PET) in oncology

Cancer cells show increased metabolism of both glucose and amino acids, which can be monitored with 18F-2-deoxy-2-fluoro-D-glucose (FDG), a glucose analogue, and 11C-L-methionine (Met), respectively. FDG uptake is higher in fast-growing than in slow-growing tumors. FDG uptake is considered to be a good marker of the grade of malignancy. Several studies have indicated that the degree of FDG uptake in primary lung cancer can be used as a prognostic indicator. Differential diagnosis of lung tumors has been studied extensively with both computed tomography (CT) and positron emission tomography (PET). It has been established that FDG-PET is clinically very useful and that its diagnostic accuracy is higher than that of CT. Detection of lymph node or distant metastases in known cancer patients using a whole-body imaging technique with FDG-PET has become a good indication for PET. FDG uptake may be seen in a variety of tissues due to physiological glucose consumption. Also FDG uptake is not specific for cancer. Various types of active inflammation showed FDG uptake to a certain high level. Understanding of the physiological and benign causes of FDG uptake is important for accurate interpretation of FDG-PET. In monitoring radio/chemotherapy, changes in FDG uptake correlate with the number of viable cancer cells, whereas Met is a marker of proliferation. Reduction of FDG uptake is a sensitive marker of viable tissue, preceding necrotic extension and volumetric shrinkage. FDG-PET is useful for the detection of recurrence and for monitoring the therapeutic response of tumor tissues in various cancers, including those of the lung, colon, and head and neck. Thus, PET, particularly with FDG, is effective in monitoring cancer cell viability, and is clinically very useful for the diagnosis and detection of recurrence of lung and other cancers.

2-[Fluorine-18]-fluoro-2-deoxy-d-glucose positron emission tomography in the diagnosis of recurrent ovarian cancer

OBJECTIVE

The aim of the study was to investigate the role of 2-[fluorine-18]-fluoro-2-deoxy-d-glucose positron emission tomography (FDG PET) in the diagnosis of recurrent ovarian cancer.

METHODS

One hundred six FDG PET scans performed in 54 patients in the follow-up after cytoreductive surgery and chemotherapy of ovarian cancer were reevaluated. Fifty-eight scans were performed in patients with suspected recurrence and 48 scans in patients who were clinically disease free. Thirty-seven PET scans were validated by histology and 66 studies by a median follow-up of 22 months in disease-free patients or 12 months in patients with recurrent disease. Three scans were validated by concordant positive findings of tumor marker CA125, computed tomography, and FDG PET.

RESULTS

FDG PET correctly identified recurrent disease in 73/88 cases. PET ruled out recurrent disease in 15/18 cases. The sensitivity and specificity for PET were 83 and 83%, respectively. In patients with suspected disease, sensitivity was 94% compared to 65% in patients judged clinically disease free. The sensitivity of PET was 96% if suspicion of recurrence was based on a rise of CA125 alone. PET preceded the conventional diagnosis by a median of 6 months in patients judged clinically free of disease. The median relapse-free interval after a negative PET scan was 20 months.

CONCLUSION

FDG PET provides the chance to detect recurrent ovarian cancer at an earlier stage during follow-up. Patients with a negative PET scan have a longer relapse-free interval than patients with a positive PET scan.

Positron emission tomography (PET) for staging low-grade non-Hodgkin's lymphomas (NHL)

Although positron emission tomography (PET) imaging is now recognized as a useful tool for staging intermediate and high-grade non-Hodgkin's lymphoma (NHL), few data are available regarding its accuracy in low grade NHL. We therefore studied 36 patients with histologically proven low-grade NHL. Whole-body 2-(fluorine-18) fluoro-2-deoxy-D-glucose (FDG) PET was performed at the time of initial diagnosis (n = 21) or for disease recurrence (n = 15) prior to any treatment. PET results were compared to those of physical examination and computed tomography (CT). PET studies were read without knowledge of any clinical data. Any focus of increased activity was described and given a probability of malignancy using a 5 point-scale (0: normal to 4: definitively malignant). An individual biopsy was available for a total of 31 lesions. The sensitivity and specificity were 87% and 100% for FDG-PET, 100% and 100% for physical examination and 90% and 100% for CT respectively. In addition, 42 of 97 peripheral lymph node lesions observed by FDG-PET were clinically undetected, whereas the physical examination detected 23 additional nodal lesions. PET and CT both indicated 12 extranodal lymphomatous localizations. FDG-PET showed 7 additional extranodal lesions while 5 additional unconfirmed lesions were observed on CT. Regarding bone marrow infiltration, PET and biopsy were concordant in 24 patients with 11 true positive (TP) and 13 true negative (TN). However PET was FN in 11 patients and no biopsy was performed in one patient. The combination PET/CT/physical examination seems to be more sensitive than the conventional approach for staging low grade NHL. Its sensitivity however is unacceptably low for diagnosing bone marrow infiltration.

Correlation of FDG-PET imaging with Glut-1 and Glut-3 expression in early-stage non-small cell lung cancer

PURPOSE

To correlate FDG activity on PET with the expression of glucose transporter proteins Glut-1 and Glut-3 in patients with early stage non-small cell lung cancer (NSCLC).

METHODS

Over a 5 year period, all patients with a PET scan and clinical stage I NSCLC underwent an immunohistochemical analysis of their tumor for Glut-1 and Glut-3 expression. The amount of FDG uptake in the primary lesion was measured by a standardized uptake ratio (SUR) and correlated with immunohistochemical results.

RESULTS

Seventy-three patients with a mean age of 66 years had clinical stage I disease. The final pathologic stage showed 64 patients with stage IA/B disease, eight with stage IIA disease, and one patient with pathologic stage IIIA (T1N2) disease. Glut-1 transporter expression was significantly higher than Glut-3 (P<0.0001), and although there was some association between the SUR and Glut-1 (P=0.085) and SUR and Glut-3 (P=0.074) expression, this did not reach statistical significance.

CONCLUSIONS

Glut-1 and Glut-3 transporter expression did not demonstrate a statistically significant correlation with FDG uptake in potentially resectable lung cancer. It appears that these transporters alone do not affect the variation in FDG activity in early stage NSCLC.

A basic study on lesion detectability for hot spot imaging of positron emitters with dedicated PET and positron coincidence gamma camera

The aim of this study was to explore the correlations of detectability and the semi-quantification for hot spot imaging with positron emitters in positron emission tomography (PET) and with a positron coincidence detection system (PCD). Phantom study results for the measurement of the lesion-to-background (L/B) ratio ranged from 2.0 to 30.3, and detectability for hot spot lesion of PET and PCD were performed to correspond to clinical conditions. The detectability and semi-quantitative evaluation of hot spots from 4.4 mm to 36.9 mm in diameter were performed from the PET and PCD images. There were strong correlations between the L/B ratios derived from PET and PCD hot spot images and actual L/B ratios; but the L/B ratio derived from PET was higher than that from PCD with a significant difference of 10% to 54.8%. The detectability of hot spot imaging of PCD was lower than that of PET at 64.8% (PCD) versus 77.8% (PET). Even the actual L/B ratio was 8.0, hot spots more than 10.6 mm in diameter could be clearly identified with PCD imaging. The same identification could be achieved with PET imaging even when the actual L/B ratio was 4.0. This detailed investigation indicated that FDG PCD yielded results comparable to FDG PET on visual analysis and semi-quantitative analysis in detecting hot spots in phantoms, but semi-quantitative analysis of the L/B ratio with FDG PCD was inferior to that with FDG PET and the detectability of PCD in smaller hot spots was significantly poor.

Metastatic thyroid cancer occurring as an unknown primary lesion: the role of F-18 FDG positron emission tomography

Thyroid cancer can appear as metastatic disease of an unknown primary origin, and fluorine-18 fluorodeoxyglucose (F-18 FDG) positron emission tomographic (PET) studies are helpful in the workup evaluation of these patients. The authors describe two patients who had metastatic disease from an unknown primary lesion. F-18 FDG PET studies played an important role in localizing the primary malignant site in the thyroid gland. The utility of F-18 FDG imaging in decreasing the number of procedures, cost, and inconvenience to patients is shown clearly in both cases.

Radioassays and experimental evaluation of dose calibrator settings for 18F

The positron emitter 18F continues to be one of the most important imaging radionuclides in diagnostic nuclear medicine. Assays of radiopharmaceuticals containing this nuclide are often performed in the clinic using commercial reentrant ionization chambers, or "dose calibrators". Meaningful quantitative clinical studies require accurate knowledge of the injected activity which requires proper calibration of these instruments. Radioassays were performed at the National Institute of Standards and Technology (NIST) on a solution of 18F produced at the National Institutes of Health (NIH) using 4pibeta liquid scintillation (fS) counting with 3H-standard efficiency tracing. Cocktails containing water fractions of approximately 0.9 and 9% (both as saline) were used. The massic activity values were measured to be 2.52+/-0.06 and 2.50+/-0.03 MBq g(-1), respectively, for the 0.9 and 9% water cocktails as of the reference time. The uncertainties on the activity measurements are expanded (k = 2) uncertainties. The largest uncertainty component was found to be the repeatability on a single LS source, with the cocktails containing 0.9% water fraction exhibiting a larger variability by nearly a factor of two. Reproducibility between LS cocktails with the same water fraction was also found to be a large uncertainty component, but with a value less than half that due to measurement repeatability. Radionuclidic impurities consisted of 48V and 46Sc, at levels of 0.11+/-0.08% (expanded uncertainties) and approximately 2 x 10(-3)% (upper limit) relative to the activity of the 18F, as of the reference time. Dose calibrator dial settings for measuring solutions of 18F were experimentally determined for Capintec CRC-12 and CRC-35R dose calibrators in three measurement geometries: a 5-ml standard NIST ampoule (two ampoules measured), a 12-ml plastic syringe containing 9 ml of solution and a 10-ml Mallinckrodt molded dose vial filled with 5 ml of solution. The experimental dial settings (and the corresponding expanded uncertainties) for these geometries were found to be 477+/-7, 474+/-6, 482+/-6 and 463+/-7 for the two ampoules, the syringe and the dose vial, respectively, in the CRC-12. The dial settings determined for the CRC-35R were 472+/-7, 470+/-7, 464+/-6 and 456+/-6 for the two ampoules, the syringe, and the dose vial, respectively. The uncertainties in the dial settings are expanded uncertainties. Comparisons between the empirically determined dial settings and the manufacturer's recommended setting of "439" indicate that use of the manufacturer's setting overestimates the activity by between 3 and 6%, depending upon the geometry used.

[76Br]Bromodeoxyuridine PET in tumor-bearing animals

5-bromodeoxyuridine (BUdR) provides in vitro measures of tumor cell proliferation. We used positron emission tomography to study tissue and plasma kinetics of [76Br]BUdR in tumor-bearing animals. In order to account for the slow washout of the major plasma metabolite, [76Br]bromide, a mathematical correction for the distribution volume of [76Br]bromide was applied. However, following correction specific tumor tracer retention was low or even zero and did not correlate with independent measures of proliferation. The kinetic characteristics of [76Br]BUdR make this tracer unsuitable for proliferation imaging.

Current status of positron emission tomography in oncology

Positron emission tomography (PET) has emerged as a powerful diagnostic tool in oncology patients. There is evidence of the superior utility over conventional imaging methods of the principal PET tracer 18F-fluoro-2-deoxy-glucose in the staging of a range of cancers and monitoring disease recurrence, as well as changing patient management to more appropriate therapy. The methods for evaluating the evidence for PET remain complex, particularly as the standard evidence-based approach of randomized controlled trials is not generally applicable to imaging technologies. PET has the potential to dramatically improve our ability to manage patients with cancer and is also making major contributions to the development of new therapies.

Application of positron emission tomography imaging to cancer screening

Whole-body positron emission tomography (PET) with(18)F-fluorodeoxyglucose (FDG) is a diagnostic modality that can noninvasively survey the entire body and sensitively detect various cancers. In this study, we examined the potential application of whole-body PET for cancer screening in asymptomatic individuals. PET was performed in conjunction with conventional examinations including physical examination, laboratory study, ultrasonography and chest computed tomography. Between September 1994 and March 1999, 3165 asymptomatic individuals participated in 5575 screening sessions (2017 men and 1148 women; mean +/- SD age, 52.2+/-10.4 years). Follow-up periods were no less than 10 months. PET results were compared with the screening outcomes. Within 1 year after screening, malignant tumours were discovered in 67 of the 3165 participants (2.1%). PET findings were true-positive in 36 of the 67 cancers (54%). Most of the 36 patients underwent potentially curative surgery; thus a wide variety of cancers were detected by PET at potentially curable stages. However, PET findings were false-negative in 31 of the 67 patients (46%). 14 of these 31 (45%) were of urological origin. FDG PET imaging has the potential to detect a wide variety of cancers at potentially curable stages. However, PET imaging is not suited to screening test of general population because PET examination involves substantial cost.

Positron emission tomography of experimental melanoma with

Positron emission tomography (PET) has evolved as a new diagnostic modality in cancer patients. Thioureylenes, such as thiouracil and methimazole, are known to be incorporated into growing melanin and selectively retained in melanotic melanoma. In the present study we used [(76)Br]5-bromo-2-thiouracil as tracer for PET imaging of human and murine melanotic melanoma transplanted subcutaneously into rats. The melanomas were clearly depicted 1 day after the injection, when [(76)Br]5-bromo-2-thiouracil was retained in the tumors though the overall radioactivity concentration in the body had declined. Accumulation of (76)Br was also seen in bladder, liver, and kidney. In addition, the rats were simultaneously injected with [(125)I]5-iodo-2-thiouracil and the tissue distribution of radioactivity was mapped by whole-body autoradiography. The results confirmed the selective uptake of thiouracil in the melanoma where the concentration of (125)I-radioactivity was about three-fold higher than that in the liver and lungs. These results show the possibility of using [(76)Br]5-bromo-2-thiouracil for PET diagnostics of melanoma, including dosimetry, prior to targeted therapy using [(131)I]5-iodo-2-thiouracil or [(211)At]5-astato-2-thiouracil.

Whole-body FDG positron emission tomographic imaging for staging esophageal cancer comparison with computed tomography

PURPOSE

The aim of the authors in this study was to critically evaluate the role of whole-body positron emission tomographic (PET) imaging with fluorine-18 fluorodeoxyglucose (FDG) in staging esophageal cancer, and further to compare this method with conventional imaging with computed tomography (CT).

MATERIALS AND METHODS

The authors performed independent, blinded retrospective evaluations of FDG PET images obtained in 47 patients referred for the initial staging of esophageal cancer before minimally invasive surgical staging. Twenty PET studies from patients with nonesophageal thoracic cancers were randomly selected for inclusion in the PET readings. In a subset of 37 of 47 cases, the PET findings were compared with independent readings of CT studies acquired within the same 6-week interval. The utility of the imaging findings was evaluated using a high-sensitivity interpretation (i.e., assigning equivocal findings as positive) and a low-sensitivity interpretation (i.e., assigning equivocal findings as negative).

RESULTS

PET was less sensitive (41% in high-sensitivity mode, 35% in low-sensitivity mode) than CT (63% to 87%) for diagnosing tumor involvement in locoregional lymph nodes, which was identified by surgical assessment in 72% of patients. Notable, however, was the greater specificity of PET-determined nodal sites (to approximately 90%) compared with CT (14% to 43%). In detecting histologically proved distant metastases (n = 10), PET performed considerably better when applied in the high-sensitivity mode, with a sensitivity rate of approximately 70% and a specificity rate of more than 90% in the total group and in the subset of patients with correlative CT data. In the low-sensitivity mode, CT identified only two of seven metastatic sites, whereas the high-sensitivity mode resulted in an unacceptably high rate of false-positive readings (positive predictive value, 29%). PET correctly identified one additional site of metastasis that was not detected by CT.

CONCLUSIONS

The relatively low sensitivity of PET for identifying locoregional lesions precludes its replacement of conventional CT staging. However, the primary advantage of PET imaging is its superior specificity for tumor detection and improved diagnostic value for distant metastatic sites, features that may substantially affect patient management decisions. In conclusion, PET imaging is useful in the initial staging of esophageal cancer and provides additional and complementary information to that obtained by CT imaging.

Evaluation of chemotherapy response in primary bone tumors with F-18 FDG positron emission tomography compared with histologically assessed tumor necrosis

PURPOSE

The purpose of this study was to evaluate the potential of positron emission tomography using F-18-fluoro-2-deoxy-D-glucose (FDG PET) to assess the chemotherapy response of primary osseous tumors compared with the degree of necrosis determined histologically.

PATIENTS AND METHODS

Seventeen patients with primary bone tumors (11 osteosarcomas, 6 Ewing's sarcomas) were examined using FDG PET and planar bone scintigraphy before neoadjuvant chemotherapy and before surgery. Tumor response was classified histologically according to Salzer-Kuntschik (grades I-II: good response; grades IV-VI: poor response). In both imaging methods, quantification was performed using tumor to nontumor ratios (T:NT).

RESULTS

Histologically, 15 patients were classified as having good responses (grade I, n = 1; grade II, n = 6; grade III, n = 8) and two as having poor responses (grades IV and V). FDG PET showed more than a 30% decrease in T:NT ratios in all patients who had good responses. However, three of these patients had increasing bone scintigraphy T:NT ratios, and another five had decreasing ratios of less than 30%. The patients with poor responses had increasing T:NT ratios and decreasing ratios of less than 30%, respectively, using both imaging methods.

CONCLUSIONS

FDG PET seems to be a promising tool for evaluating the response of primary osseous tumors to chemotherapy. In this preliminary study, FDG PET was superior to planar bone scintigraphy.

Effect of nitroimidazole sensitizers on in vitro glycolytic metabolism of hypoxic squamous cell carcinoma

Two nitroimidazole compounds, misonidazole (MISO) and nimorazole (NIMO), were evaluated for their potential to modify uptake of [5,6-3H] 2-fluoro-2-deoxy-D-glucose (3H-FDG) in the human squamous carcinoma cell line UT-SCC-5 exposed to increasing levels of hypoxia. UT-SCC-5 cells were incubated with 0-10 mM of MISO or NIMO under normal or reduced oxygen concentrations of 20%, 1.5%, or 0% with 5% CO2 for 6 h, after which 74 KBq of 3H-FDG was added in media for 1 h. In the presence of normal concentrations of O2, both sensitizers increased 3H-FDG uptake by up to 178% (MISO) or 84% (NIMO) when compared with untreated cells. In anoxia, MISO decreased 3H-FDG uptake to 35% of that of control whereas NIMO-treated cells showed a respective decrease in tracer uptake to 62%. Clonogenic assays clearly indicated that MISO was toxic and NIMO moderately toxic for hypoxic cells, whereas both sensitizers exerted only a very modest effect on survival of fully oxygenated cells. Our findings indicate that nitroimidazole treatment consistently increases 3H-FDG uptake into UT-SCC-5 cells under normal oxygen concentrations. In hypoxia, the observed decrease in tracer uptake is dependent on both the level of ambient oxygen and drug concentration and may reflect both direct toxicity and inhibition of glycolysis. The observations may be useful for further applications of 18F-FDG positron emission tomography (PET) to monitor effects of hypoxic cell radiosensitizers on tumor metabolism in vivo.

Evaluation of lung cancer by 99mTc-tetrofosmin SPECT: comparison with [18F]FDG-PET

PURPOSE

The purpose of this study was to clarify the validity of (99m)Tc-tetrofosmin SPECT (TF-SPECT) in the evaluation of lung cancer in comparison with [18F]fluorodeoxyglucose ([18F]FDG-PET).

METHOD

Twenty-one patients with biopsy-proven non-small cell lung cancer were examined by both TF-SPECT (early and delayed images) and FDG-PET within a week of each study. Lung cancers were analyzed visually and semiquantitatively using the ratio of lesion to background counts (L/B ratio). Mediastinal lymph node metastases were analyzed only visually.

RESULTS

Both early and delayed TF images could detect 18 of 21 lung cancers on visual analysis (85.7%), whereas FDG-PET could detect all the lesions (100%). The L/B ratio of TF-SPECT was significantly higher in delayed than in early images (1.79 +/- 0.55 vs. 1.56 +/- 0.40; p < 0.001). However, the L/B ratio of FDG-PET was 8.85 +/- 3.05, significantly higher than those of both TF images (p < 0.0001). In the assessment of mediastinal involvement, TF-SPECT was 40.0% sensitive, 100% specific, and 71.4% accurate, whereas FDG-PET was 80.0% sensitive, 81.8% specific, and 81.0% accurate.

CONCLUSION

Although the detection sensitivity was far better than expected, TF-SPECT is not considered to be an alternative to FDG-PET in the evaluation of malignant pulmonary lesions because of its significantly low L/B ratio. TF-SPECT has poor sensitivity for mediastinal lymph node metastases and is useless for staging patients with lung cancer.

Cellular release of [18F]2-fluoro-2-deoxyglucose as a function of the glucose-6-phosphatase enzyme system

[(18)F]-2-Fluoro-2-deoxyglucose (FDG) is a glucose analog currently utilized for positron emission tomography imaging studies in humans. FDG taken up by the liver is rapidly released. This property is attributed to elevated glucose-6-phosphatase (Glc-6-Pase) activity. To characterize this issue we studied the relationship between Glc-6-Pase activity and FDG release kinetics in a cell culture system. We overexpressed the Glc-6-Pase catalytic unit in a Glc-6-Pase-deficient mouse hepatocyte (Ho-15) and in A431 tumor cell lines. Glc-6-Pase enzyme activity and FDG release rates were determined in cells transfected with the Glc-6-Pase gene (Ho-15-D3 and A431-AC3), in mock-transfected cells of both cell lines, and in wild-type mouse hepatocytes (WT10) as control. Although the highest level of Glc-6-Pase activity was measured in A431-AC3, Ho-15-D3 cells showed much faster FDG release rates. The faster FDG release correlated with the level of glucose 6-phosphate transporter (Glc-6-PT) mRNA, which was found to be expressed at higher levels in Ho-15 compared with A431 cells. Overexpression of Glc-6-PT in A431-AC3 produced a dramatic increase in FDG release compared with control cells. This study gives the first direct evidence that activity of the Glc-6-Pase complex can be quantified in vivo by measuring FDG release. Adequate levels of Glc-6-Pase catalytic unit and Glc-6-PT are required for this function. FDG-positron emission tomography may be utilized to evaluate functional status of the Glc-6-Pase complex.

Non-small cell lung cancer: FDG PET for nodal staging in patients with stage I disease

PURPOSE

To determine the accuracy of 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography (PET) in the evaluation of regional lymph nodes in patients with stage I non-small cell lung cancer (NSCLC).

MATERIALS AND METHODS

Imaging and clinical findings obtained during 5 years in 84 patients (mean age, 66 years) were reviewed. Patients had thoracic computed tomographic findings of stage I NSCLC, an FDG PET study, and histopathologic proof of lung cancer. At the time of diagnosis, disease stage was assigned on the basis of FDG PET results and was compared with the histopathologic stage to determine the accuracy of PET.

RESULTS

When PET stage was compared with histopathologic stage, the disease in 72 (86%) patients was accurately staged with PET, understaged in two (2%), and overstaged in 10 (12%). The overall sensitivity, specificity, and positive and negative predictive values for PET of regional lymph nodal metastases were 82%, 86%, 47%, and 97%, respectively.

CONCLUSION

FDG PET enables accurate staging of regional lymph node disease in patients with stage I NSCLC. A negative PET scan in these patients suggests that mediastinoscopy is unnecessary and that these patients can proceed directly to thoracotomy.

Lung cancer and positron emission tomography with fluorodeoxyglucose

Over the past years, positron emission tomography (PET) with fluoro-2-deoxy-D-glucose (FDG) has emerged as an important imaging modality. In the thorax, FDG-PET has been shown to differentiate benign from malignant pulmonary lesions and stage lung cancer. Preliminary studies have shown its usefulness in assessing tumor recurrence, and assisting in radiotherapy planning. FDG-PET is often more accurate than conventional imaging studies, and has been proven to be cost-effective in evaluating lung cancer patients. This review will discuss the current applications of FDG-PET as compared with conventional imaging in diagnosing, staging, and following patients with lung cancer.

Prognostic value of thoracic FDG PET imaging after treatment for non-small cell lung cancer

OBJECTIVE

We determined the prognostic value of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) for patients with treated lung cancer.

MATERIALS AND METHODS

We examined patients who underwent FDG PET after first-line treatment for non-small cell lung cancer. FDG PET results were correlated with survival rates to determine whether FDG PET findings were predictive of outcomes.

RESULTS

After initial therapy, 113 patients with non-small cell lung cancer underwent FDG PET. One hundred patients had positive FDG PET results and a median survival of 12 months (95% confidence interval, 9.2-15.4). Thirteen patients had negative FDG PET results, and 11 (85%) of these patients are still living at a median follow-up of 34 months. The difference in survival for patients with positive and negative FDG PET results was statistically significant (p = 0.002).

CONCLUSION

FDG PET has prognostic value and strongly correlates with survival rates of patients with treated lung cancer. Patients with positive FDG PET results have a significantly worse prognosis than patients with negative results. Additionally, FDG PET may be helpful in guiding therapeutic treatments.

Demonstration of [11C] 5-hydroxy-L-tryptophan uptake and decarboxylation in carcinoid tumors by specific positioning labeling in positron emission tomography

In three patients with carcinoid liver and/or lymph node metastases, we studied the process of tumor tracer uptake and decarboxylation by means of positron emission tomography (PET) using 5-hydroxy-L-tryptophan (5-HTP) 11C-labeled in the beta-position (HTP) and later the same day with 5-HTP 11C-labeled in the carboxyl group (HTC). With HTP, in which the 11C-label follows the molecule through decarboxylation to form 11C-serotonin, a high tumor accumulation of the tracer was found. With HTC, in which the label is rapidly eliminated from the tissues as 11CO2 if decarboxylation takes place, there was virtually no uptake by the tumors. By utilizing data from PET scanning with both tracers, we could quantify the decarboxylation rate and tissue accumulation of [11C]-serotonin and hence the enzymatic action of aromatic amino acid decarboxylase.

Solitary pulmonary nodules: Part II. Evaluation of the indeterminate nodule

Various strategies may be used to evaluate indeterminate solitary pulmonary nodules. Growth rate assessment is an important and cost-effective step in the evaluation of these nodules. Clinical features (eg, patient age, history of prior malignancy, presenting symptoms, smoking history) can be useful in suggesting the diagnosis and aiding in management planning. Bayesian analysis allows more precise determination of the probability of malignancy (pCa). Decision analysis models suggest that the most cost-effective management strategy depends on the pCa for a given nodule. At contrast material-enhanced computed tomography, nodular enhancement of less than 15 HU is strongly predictive of a benign lesion, whereas enhancement of more than 20 HU typically indicates malignancy. At 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG) positron emission tomography, lesions with low FDG uptake are typically benign, whereas those with increased FDG uptake are typically malignant. Results of transthoracic needle aspiration biopsy influence management in approximately 50% of cases and, in indeterminate lesions with a pCa between 0.05 and 0.6, is the best initial diagnostic procedure. It is optimally used in peripheral nodules and has been reported to establish a benign diagnosis in up to 91% of cases. Although there is no one correct management approach, the ability to distinguish benign from malignant solitary pulmonary lesions has improved with the use of these strategies.

Positron emission tomography imaging in the thorax

Positron emission tomography imaging has proven valuable in the evaluation and management of thoracic abnormalities. It is more accurate than CT or MR imaging in characterizing indeterminate focal abnormal pulmonary opacities, staging lung cancer, and assessing the therapeutic response. PET imaging in lung cancer also appears to be cost-effective, particularly with whole-body studies. The metabolic and physiologic abnormalities used in FDG-PET imaging, rather than conventional anatomic or morphologic characteristics, provide an invaluable model for the future of tumor imaging.

High yield direct 76Br-bromination of monoclonal antibodies using chloramine-T

Monoclonal antibody (MAb) A33 was labeled with the positron emitter 76Br (T(1/2) = 16.2 h). Direct labeling was done using the conventional chloramine-T method. After optimization of the labeling conditions, a maximum yield (mean +/- max error) of 77 +/- 2% was obtained at pH 6.8. In vitro binding of 76Br-A33 to SW1222 colonic cancer cells showed that the immunoreactivity was retained. Also, the MAbs 38S1 and 3S193 and the peptide hEGF were 76Br-labeled, resulting in labeling yields (mean +/- max error) of 75 +/- 3%, 63 +/- 4%, and 73 +/- 0.1%, respectively. We conclude that antibodies and peptides can be labeled conveniently with 76Br for the purpose of whole-body tumour imaging by positron emission tomography.

Metastases from non-small cell lung cancer: mediastinal staging in the 1990s--meta-analytic comparison of PET and CT

PURPOSE

To meta-analytically compare 2-[fluorine 18]fluoro-2-deoxy-D-glucose positron emission tomography (PET) and computed tomography (CT) for the demonstration of mediastinal nodal metastases in patients with non-small cell lung cancer.

MATERIALS AND METHODS

English-language reports on the diagnostic performance of PET (14 studies, 514 patients) and/or CT (29 studies, 2,226 patients) for demonstration of mediastinal nodal metastases from NSCLC were selected by using the MEDLINE database. In eligible studies, an objective diagnostic standard was used, data were presented to allow recalculation of contingency tables, and established diagnostic criteria were used for abnormal test results. Summary receiver operating characteristic (ROC) curves were calculated.

RESULTS

Pooled point estimates of diagnostic performance and summary ROC curves indicated that PET was significantly more accurate than CT for demonstration of nodal metastases (P < .001). Mean sensitivity and specificity (+/- 95% CI) were 0.79 +/- 0.03 and 0.91 +/- 0.02, respectively, for PET and 0.60 +/- 0.02 and 0.77 +/- 0.02, respectively, for CT. The log odds ratios were 1.79 (95% CI: 1.49, 2.09) for CT and 3.77 (95% CI: 2.77, 4.77) for PET (P < .001). Subgroup analyses did not alter findings.

CONCLUSION

PET is superior to CT for mediastinal staging of non-small cell lung cancer, independent of performance index or clinical context of PET imaging.

Positron Emission Tomography Imaging in Lung Cancer

Over the past several years, positron emission tomography (PET) has become a clinically useful, noninvasive study which complements conventional imaging (chest radiographs, computed tomography [CT], and magnetic resonance imaging [MRI]) in the evaluation of patients with lung cancer. PET imaging of lung cancer is typically performed with the radiopharmaceutical 18F-2-deoxy-D-glucose (FDG), a d-glucose analog. Increased glucose metabolism by malignant cells results in increased uptake and accumulation of FDG, which serves as the basis for tumor detection. This review will focus on the current applications of FDG-PET in lung cancer patients including evaluation of focal pulmonary abnormalities, staging lung cancer, determining tumor recurrence, and in assessing prognosis.

Imaging of locally recurrent and metastatic thyroid cancer with positron emission tomography

Serum thyroglobulin and imaging have been routinely used in the evaluation of thyroid cancer patients suspected of having metastatic or recurrent disease. A more sensitive technique capable of identifying the sites of disease not detected by current imaging methods might improve overall management. The objective in this study was to demonstrate the feasibility of using positron emission tomography (PET) for the detection of recurrent thyroid cancer. Thirty patients with a history of either papillary/follicular or medullary thyroid cancer suspected of having locally recurrent or metastatic cancer on the basis of elevated or rising blood markers were evaluated with PET. Imaging studies were performed with the radiotracer [F-18] fluorodeoxyglucose (FDG). A retrospective review of other imaging results was performed and compared to the PET results. PET was able to identify locally recurrent or metastatic papillary/follicular disease in all 24 patients studied with elevated or rising thyroglobulin. Similar results were obtained in 6 patients with medullary cancer recurrences in the presence of elevated calcitonin. In cases where follow-up data was obtainable (17/24 papillary/follicular cancers and 4/6 medullary cancers), disease was confirmed either directly by surgery and/or indirectly through changes or persistence of laboratory findings. The results support the hypothesis that in the presence of elevated blood markers indicative of recurrent thyroid cancer, PET may prove valuable as an adjunctive imaging test for identifying disease and influencing management in cases where conventional imaging fails to detect suspected disease.