Radionuclide evaluation of patients with lymphoma

PET imaging for pediatric oncology: an assessment of the evidence

Positron emission tomography (PET) has shown potential benefits when used in therapeutic clinical trials for children with cancer. However, existing trials are limited in scope with small numbers of patients and varied observations, making accurate conclusions about the usefulness of PET scanning impossible. This review examines PET and its applications in pediatric oncology. While evidence is limited, there appears to be a basis for rigorous evaluation of this imaging modality before widespread application without validation from clinical trials.

FDG positron emission tomography/computed tomography studies of Wilms' tumor

PURPOSE

The purpose of this analysis was to evaluate the utility of FDG PET/CT scanning in patients with Wilms' tumors.

METHODS

A total of 58 scans were performed in 27 patients (14 male, 13 female; ages: 1.9-23 years, median: 7 years) with proven Wilms' tumor. Twenty-six patients (56 scans) were studied at the time of suspected relapse, progressive disease, persistent disease, or for monitoring of therapy.

RESULTS

In the 27 patients with Wilms' tumor, 34 scans showed areas of abnormal uptake consistent with metabolically active tumors. Of the patients, 8 (24 scans) had pulmonary metastases larger than 10 mm in diameter, 10 (12 scans) had hepatic metastases, 11 (11 scans) had regional nodal involvement, 3 (3 scans) had bone metastases, 1 (1 scan) had chest wall involvement, 2 (2 scans) had pancreatic metastasis, and 5 (5 scans) had abdominal and pelvic soft tissue involvement. Two of eight patients with lung metastases had variable uptakes. Lung lesions 10 mm or smaller were not consistently visualized on PET scans. One patient with a liver metastasis showed no uptake on PET scan after treatment (size decreased from 45 to 15 mm).

CONCLUSION

Most Wilms' tumors concentrate FDG. However, small pulmonary metastases may be better visualized with CT. FDG PET/CT appears useful for defining the extent of involvement and assessing the response to treatment.

Direct comparison of FDG PET and CT findings in patients with lymphoma: initial experience

PURPOSE

To retrospectively compare fluorine 18 fluorodeoxyglucose (FDG) positron emission tomographic (PET) and computed tomographic (CT) findings at the same anatomic locations in patients with lymphoma by using a combined PET/CT scanner and to analyze the lesions on metabolic and anatomic bases to evaluate causes of discrepant findings between the two modalities.

MATERIALS AND METHODS

The institutional review board allowed an exempt retrospective review of cancer PET database, and informed consent was waived. The study was HIPAA compliant. Fifty-three patients with lymphoma (20 Hodgkin and 33 non-Hodgkin; mean age, 43 years; range, 12-83 years) who underwent FDG PET/CT were included. The PET and CT images were interpreted by two nuclear medicine physicians and one radiologist, respectively, blinded to the other imaging findings. Concordant PET and CT findings were regarded as positive or negative for lymphoma. The site with discordant findings was defined as positive for disease if it was accompanied by other PET- and CT-positive sites in the same patient or was confirmed clinically (histologic examination or progressive disease). Staging results were also compared by one nuclear medicine physician.

RESULTS

Of a total of 1537 anatomic sites in 53 patients, 48 had discordant findings between PET and CT. Forty (83%) of the 48 sites had correct PET findings (31 positive, nine negative), five had correct CT findings, and three were unresolved. The 31 PET-positive and CT-negative sites accounted for 23% of all 134 true-positive PET sites. PET provided accurate staging in an incremental nine (17%, upstaging in four and downstaging in five) of 53 patients in whom CT staging was incorrect. CT provided correct upstaging in two patients.

CONCLUSION

FDG PET/CT as a combined modality may contribute substantially to lesion characterization and staging in patients with lymphoma.

Coincidence-detection FDG-PET versus gallium in children and young adults with newly diagnosed Hodgkin's disease

Coincidence-detection 18F-FDG-PET (PET) and 67Ga whole-body and SPECT (Ga) were compared in children and young adults with newly diagnosed Hodgkin's disease (HD).

MATERIALS AND METHODS

Thirty patients with histologically confirmed HD underwent PET with attenuation correction 1 h after injection of 150-220 MBq 18F-FDG and whole-body and SPECT imaging 72 h after injection of 250-370 MBq 67Ga citrate. Two experienced readers retrospectively reviewed PET and Ga scans, grading 13 anatomic regions from one (normal) to five (abnormal). Numerical stages were assigned based on Ann Arbor classification. Comparison was made with disease sites (established by biopsy or two or more of the following: physical examination, conventional imaging studies, radionuclide studies, and follow-up studies) and clinical stages. Sensitivity, specificity, and accuracy were calculated and significance of differences determined using McNemar's test.

RESULTS

PET detected 120/138 (87%) disease sites and Ga 109/138 (79%). PET and Ga were concordant for 103/138 (75%) sites. Accuracies were not significantly different for supradiaphragmatic disease. PET was more accurate than Ga for detecting splenic (0.91 vs 0.61, P = 0.012), infradiaphragmatic (0.89 vs 0.75, P = 0.042), and all disease sites combined (0.95 vs 0.91, P = 0.039). PET stage agreed with clinical stage in 79% of patients and Ga in 71%.

CONCLUSION

PET was superior to Ga for evaluating children and young adults with newly diagnosed HD.

Lung hilar Ga-67 uptake in patients with lymphoma following chemotherapy

Scintigraphic characteristics of lung hilar Ga-67 uptake (HU) and their relationship with the etiology (benign vs. malignant) of the hilar lesions in lymphoma patients following chemotherapy were retrospectively investigated. A total of 161 lymphoma patients were included in the study. The presence/absence of HU and if present, symmetry/asymmetry and intensity of HU (on the basis of a 3 scale grading system) were visually and semiquantitatively assessed on transaxial sections of thorax Ga-67 SPECT. By drawing ROIs over right and left hilum, asymmetry index (AI%) was also calculated. HU was categorized as benign or malignant depending on the radiological correlation and clinical follow-up. In the malignant group, the majority of patients (85.7%) had grade 2 or grade 3 uptake and all had asymmetric pattern. However, in the benign group, grade 1 uptake was more common (66%) and was mainly symmetric (94.6%) in appearance. AI% in the malignant group (73.7 +/- 36.6) was significantly higher than in the benign group (5.7 +/- 4.9) confirming the marked asymmetry in malignant patients.

Gallium-67 scintigraphy: a cornerstone in functional imaging of lymphoma

Until recently, gallium-67 scintigraphy (GS) has been the best available functional imaging modality for evaluating patients with non-Hodgkin's lymphoma (NHL) and Hodgkin's disease (HD). The diagnostic accuracy of GS in detecting lymphoma is based on optimisation of the imaging protocol, knowledge of potential physiological and benign sites of (67)Ga uptake, and the Ga avidity characteristics of the individual lymphoma. As (67)Ga is a tumour viability agent, the role of GS is primarily at follow-up. A residual mass persisting on CT after treatment poses a common clinical dilemma: it may indicate the presence of viable lymphoma, which requires further treatment, or it can be benign, consisting of only fibrotic and necrotic tissues. GS can successfully differentiate between these conditions. Routine follow-up with GS may allow early diagnosis of recurrence and early institution of treatment. Reversion of a positive GS to a negative test, and the rapidity with which this occurs has a high predictive value for the outcome of the individual patient. Lymphoma showing a normal GS early during treatment has a better prognosis than lymphoma with persistence of pathological findings. Other tumour-seeking single-photon emitting agents, such as thallium-201, technetium-99m methoxyisobutylisonitrile and indium-111 octreotide, have been investigated in lymphoma, primarily as an alternative to GS in specific clinical settings, but are of limited value. The role of radioimmunoscintigraphy is gaining importance in conjunction with radioimmunotherapy. Fluorine-18 fluorodeoxyglucose (FDG) imaging of lymphoma using either dedicated or camera-based PET systems is gradually replacing GS for assessment of lymphoma. FDG overcomes some of the limitations of GS while sharing its tumour viability characteristics. The extensive clinical knowledge and experience accumulated over three decades with GS in lymphoma provides a solid background as well as a model for the assessment of new functional imaging techniques.

Camera-based FDG PET and 67Ga SPECT in evaluation of lymphoma: comparative study

PURPOSE

To compare gallium 67 (67Ga) scintigraphy and camera-based fluorodeoxyglucose (FDG) positron emission tomography (PET) in the evaluation of patients with lymphoma.

MATERIALS AND METHODS

The performance of 67Ga scintigraphy and camera-based FDG PET in the detection of lymphoma was retrospectively evaluated and compared in 84 patients with lymphoma, with 219 suspected sites of disease. Eighty-nine percent of patients were examined during or after treatment. Camera-based FDG PET was initiated by equivocal characterization of the status of disease based on clinical, radiologic, and 67Ga scintigraphic assessment. Findings of 67Ga scintigraphy and camera-based FDG PET were compared on a per-patient and per-site basis for the whole group, for histologic subtypes, and for anatomic locations. Comparison of sensitivity, specificity, and accuracy between the two modalities for detection of lymphoma was performed with the McNemar test.

RESULTS

There was a statistically significant difference in sensitivity, specificity, and accuracy of 67Ga scintigraphy and camera-based FDG PET at both patient- and site-based analysis. 67Ga scintigraphy helped to accurately define disease state in 63% of patients and in 33% of sites, compared with 83% and 87%, respectively, for camera-based FDG PET. For discordant findings between the two modalities, camera-based FDG PET findings were confirmed as true-positive in 71% and as true-negative in 92% of patients. Camera-based FDG PET had a significantly higher detection rate for both nodal and extranodal lymphoma sites. It provided accurate assessment of lymphoma involvement of the skeleton in 93% of sites compared with 29% for 67Ga scintigraphy and excluded active lymphoma in 10 67Ga-positive benign parahilar sites.

CONCLUSION

In this selected group of patients with lymphoma, camera-based FDG PET allowed a significantly more accurate definition of active disease compared with that allowed with 67Ga scintigraphy.

Gallium and other agents in diseases of the lung

The use of gallium for pulmonary diseases is hampered by its relative lack of specificity, typical 1- to 3-day delay between injection and imaging time, and suboptimal imaging characteristics. Other nuclear and nonnuclear imaging modalities, such as (18)F-fluorodeoxyglucose positron emission tomography (PET) and high-resolution chest computed tomography, have replaced gallium in many clinical algorithms. Yet gallium and other radiotracers, such as thallium, sestamibi, and labeled white blood cells, are useful in many specific clinical situations involving lymphoma and other neoplasias, inflammatory processes such as sarcoid and interstitial pneumonia, tuberculosis and other infections, and the acquired immune deficiency syndrome. Gallium and some of the other single-photon agents still have value in establishing a diagnosis, assessing the location and extent of disease, differentiating active disease from chronic scarring, guiding potential biopsy, and determining recurrence and response to therapy in patients with certain lung diseases, particularly when access to PET imaging is not available.