Factors associated with false-positive staging of lung cancer by positron emission tomography

BACKGROUND

Positron emission tomography imaging is gaining popularity as a noninvasive staging tool in non-small cell lung cancer. Nonmalignant processes can also affect radio-tracer uptake. This study seeks to identify factors associated with false-positive staging of mediastinal metastases.

METHODS

A retrospective review was performed of 100 patients with early stage non-small cell lung cancer referred for positron emission tomography scan evaluation. All had pathologic confirmation of their disease. Positron emission tomography scans, radiology records, operative reports, and pathology results were reviewed. Patients with positron emission tomography scans interpreted as positive for mediastinal involvement and negative pathology at operation were selected.

RESULTS

Seven patients were found to have a false-positive positron emission tomography evaluation for mediastinal metastases. All but 1 patient had a concurrent inflammatory process or an anatomic factor associated with the false positive. The sensitivity and specificity in detecting involved mediastinal nodes was 87.5% and 90.7%, respectively. The negative predictive value was 95.8%.

CONCLUSIONS

Although positron emission tomography has been established as an accurate modality to stage non-small cell lung cancer, false-positive evaluation of mediastinal metastases can occur in the setting of concurrent inflammatory lung diseases or for centrally located tumors. Pathologic evaluation of mediastinal disease should be pursued whenever suggested by a positive positron emission tomography scan especially in the face of those factors described.

Whole-body PET imaging with [18F]fluorodeoxyglucose in management of recurrent colorectal cancer

HYPOTHESIS

Metabolic imaging by positron emission tomography (PET) using [18F]fluorodeoxyglucose will be more accurate than anatomic imaging by computed tomography (CT) for detection of recurrent colorectal cancer. More accurate staging of recurrent tumor by PET will lead to more appropriate management decisions.

DESIGN

Prospective blinded study comparing PET with CT, using histologic diagnosis, serial CT imaging, and clinical follow-up as criterion standards, with a fully blinded, retrospective reinterpretation of PET studies. Changes in diagnosis resulting from PET findings were correlated with subsequent treatment and surgical findings. Potential cost savings resulting from use of PET for preoperative staging were calculated.

SETTING

Private practice in an outpatient tertiary referral center.

PATIENTS

A group of 155 consecutive patients with imaging for diagnosis or staging of recurrent colorectal cancer. Twenty-one patient (14%) were excluded due to lack of a criterion standard. Computed tomographic scans were available for comparison for 115 patients.

RESULTS

Positron emission tomographic scan sensitivity and specificity were 93% and 98%, respectively, compared with 69% and 96% for CT. Ninety-five percent confidence intervals for the differences between the modalities were 16% to 32% for sensitivity and 1% to 5% for specificity. The sensitivity of both modalities varied with anatomic site of recurrence. Positron emission tomographic scans were true positive in 12 (67%) of 18 patients with elevated serum carcinoembryonic antigen levels and negative CT findings. In 23 (29%) of 78 preoperative studies in which CT showed a single site of recurrence, PET showed tumor at additional sites. At surgery, nonresectable, PET-negative tumor was found in 7 (17%) of 42 patients who had PET evidence of localized recurrence only. Potential savings resulting from demonstration of nonresectable tumor by PET were calculated at $3003 per preoperative study.

CONCLUSIONS

Positron emission tomography was more sensitive and specific than CT for detection of recurrent colorectal cancer. Preoperative detection of nonresectable tumor by PET may avoid unnecessary surgery, and thereby reduce the cost of patient treatment.

Abnormal temporal lobe metabolism in violent subjects: correlation of imaging and neuropsychiatric findings

PURPOSE

To search for metabolic correlates of clinical and electrophysiological abnormalities in violent subjects.

METHODS

Seven subjects with histories of extremely violent behavior were studied with positron emission tomography (PET) with fludeoxyglucose F 18 (FDG), brain electrical area mapping, MR imaging, neuropsychiatric and neuropsychological testing, and clinical examination during medical evaluation associated with legal proceedings. Nine control subjects without evidence of organic brain disease were also studied with FDG-PET. Quantitative PET data were calculated as standardized uptake values comparing the highest occipital region with the lowest temporal region.

RESULTS

Temporal lobe metabolism was decreased in the study group relative to the control subjects. Medial temporal lobe metabolism was 39% lower than that in the occipital cortex in study subjects and only 27% lower than that in control subjects. These groups differed by Mann-Whitney U test and Wilcoxon's two-sample test. Metabolic differences correlated with limbic neuropsychiatric and electrophysiological abnormalities in the violent group.

CONCLUSION

In this selected population of violent subjects, FDG-PET scans showed metabolic abnormalities in the temporal lobes. These abnormalities correlated with limbic abnormalities seen at electrophysiological and neuropsychiatric evaluation.

18-Fluorodeoxyglucose uptake and survival of patients with suspected recurrent malignant glioma

BACKGROUND

After intensive initial radiation therapy for malignant glioma, magnetic resonance imaging (MRI) and computerized tomography (CT) cannot distinguish tumor progression from radiation injury.

METHODS

The authors studied the prognostic value of 18-fluorodeoxyglucose positron emission tomography (FDG-PET) in 55 patients with malignant glioma for whom MRI obtained after initial surgery and radiation therapy demonstrated enlarging, enhancing lesions consistent with either tumor progression or radiation necrosis. Forty patients (73%) had an initial diagnosis of Grade 4 malignant glioma and 15 (27%) had Grade 3 malignant glioma. The FDG-PET scans were graded visually on a four-level scale at the time of acquisition.

RESULTS

In univariate analysis, the FDG-PET score was a significant predictor of survival time after FDG-PET scanning (P = 0.005). Median survival was 10 months for patients with FDG-PET scores of 2 or 3 (glucose uptake > or = adjacent cortex) and 20 months for those with scores of 0 or 1 (glucose uptake < adjacent cortex). In multivariate proportional hazards analysis, the FDG-PET score was a significant predictor of survival (P = 0.019) in a model that included patient age, recurrence number, and FDG-PET score. There was no significant difference in the FDG-PET score hazard ratio for patients with Grade 3 or 4 tumors at initial diagnosis, first or later suspected recurrence, initial photon irradiation given with standard fractions or hyperfractionation, or stereotactic irradiation prior to FDG-PET scanning.

CONCLUSIONS

This analysis demonstrates that FDG-PET scanning has prognostic value in a cohort limited to patients with suspected recurrent high grade glioma.

Cost-effectiveness of PET imaging in clinical oncology

To be cost-effective, PET must be diagnostically accurate and effective in improving management without increasing treatment cost. To evaluate diagnostic accuracy, we performed prospective evaluations of whole-body PET imaging in staging of non-small-cell lung cancer (99 patients), detection of recurrent colorectal cancer (57 patients), diagnosis of metastatic melanoma (36 patients), and staging of advanced head and neck cancer (29 patients). In each case, PET was more accurate than anatomic imaging for determination of the presence and extent of tumor and demonstration of nonresectable disease. PET was also more accurate than conventional imaging in staging Hodgkin's disease (30 patients). We evaluated the management impact of PET retrospectively, by reviewing the treatment records of 72 patients with solitary pulmonary nodules or non-small-cell lung cancer, 68 patients with known or suspected recurrent colorectal cancer, 45 patients with known or suspected metastatic melanoma, and 29 patients with advanced head and neck tumors. PET improved patient management by avoiding surgery for nonresectable tumor and for CT abnormalities that proved to be benign by PET imaging. For determining cost impact, the costs of surgical procedures were determined from Medicare reimbursement rates, and the cost of a PET study was taken to be $1800. The savings from contraindicated surgical procedures exceeded the cost of PET imaging by ratios of 2:1 to 4:1, depending on the indication. PET was decisively more accurate and cost-effective than anatomic imaging by CT, combining improved patient care with reduced cost of management.

Staging non-small cell lung cancer by whole-body positron emission tomographic imaging

BACKGROUND

A need exists for an accurate, noninvasive means of staging non-small cell lung cancer.

METHODS

A prospective evaluation of regional and whole-body positron emission tomography (PET) imaging for staging lung cancer was carried out in 99 patients. Mediastinal PET and computed tomography findings were compared with results of surgical staging in 76 patients. Those PET and computed tomography findings that indicated possible distant metastasis were compared with biopsy results and the results of clinical and imaging follow-up.

RESULTS

Sensitivity and specificity for the diagnosis of N2 disease were 83% and 94% for PET and 63% and 73% for computed tomography, respectively. Positron emission tomography showed previously unsuspected distant metastasis in 11 patients (11%), with no demonstrated false-positive results. Normal PET findings were obtained at distant sites of computed tomography abnormality in 19 patients (19%). Clinical and imaging follow-up in 14 of these patients showed no evidence of metastasis. In 1 case, the PET result proved to be falsely negative.

CONCLUSIONS

Imaging with PET was more accurate than computed tomography for diagnosis of mediastinal and distant metastasis. Detection of unsuspected metastatic disease by PET may permit reduction in the number of thoracotomies performed for nonresectable disease.

Normal cerebellar MIBG localization. Implications in the interpretation of delayed scans

In the I-131 MIBG scans of 14 patients with neuroblastoma (86%) or pheochromocytoma/paraganglioma (14%) that were studied more than 48 hours after administration of the radiopharmaceutical, 12 (86%) had discernible cerebellar MIBG localization. A few had midbrain or diffuse cerebral uptake as well. None of the patients had cerebellar or other central nervous system signs or symptoms, and the localization is consistent with the known distribution density of central nervous system catecholamine receptors. This suggests that cerebellar MIBG localization is normal in delayed scans and that it should not be confused with neuraxial metastasis of adrenergic neuronal neoplasms.

Normal cholescintigram in In-111 WBC positive acute acalculous cholecystitis. The converse photopenic 'rim' sign

The authors report a case of a patient with acute acalculous cholecystitis whose cholescintigram was negative, but showed a pericholecystic photopenic halo. The diagnosis was confirmed by an In-111 WBC scan and histopathology.