Imaging of malignant lymphomas with F-18 FDG coincidence detection positron emission tomography

Use of positron emission tomography for response assessment of lymphoma: consensus of the Imaging Subcommittee of International Harmonization Project in Lymphoma

PURPOSE

To develop guidelines for performing and interpreting positron emission tomography (PET) imaging for treatment assessment in patients with lymphoma both in clinical practice and in clinical trials.

METHODS

An International Harmonization Project (IHP) was convened to discuss standardization of clinical trial parameters in lymphoma. An imaging subcommittee developed consensus recommendations based on published PET literature and the collective expertise of its members in the use of PET in lymphoma. Only recommendations subsequently endorsed by all IHP subcommittees were adopted.

RECOMMENDATIONS

PET after completion of therapy should be performed at least 3 weeks, and preferably at 6 to 8 weeks, after chemotherapy or chemoimmunotherapy, and 8 to 12 weeks after radiation or chemoradiotherapy. Visual assessment alone is adequate for interpreting PET findings as positive or negative when assessing response after completion of therapy. Mediastinal blood pool activity is recommended as the reference background activity to define PET positivity for a residual mass > or = 2 cm in greatest transverse diameter, regardless of its location. A smaller residual mass or a normal sized lymph node (ie, < or = 1 x 1 cm in diameter) should be considered positive if its activity is above that of the surrounding background. Specific criteria for defining PET positivity in the liver, spleen, lung, and bone marrow are also proposed. Use of attenuation-corrected PET is strongly encouraged. Use of PET for treatment monitoring during a course of therapy should only be done in a clinical trial or as part of a prospective registry.

A metaanalysis of 18F-2-deoxy-2-fluoro-D-glucose positron emission tomography in the staging and restaging of patients with lymphoma

BACKGROUND

In recent years, the use of positron emission tomography (PET) has become widespread for the staging and follow-up of several malignancies. In the current study, the authors conducted a metaanalysis of the published literature to evaluate the diagnostic performance of 18F-2-deoxy-2-fluoro-D-glucose PET (FDG-PET) in the staging of patients with lymphoma.

METHODS

The authors conducted a systematic MEDLINE search of articles published between January 1995 and June 2004. Studies that evaluated FDG-PET with a dedicated camera and that reported sufficient data to permit the calculation of sensitivity and specificity were included in the analysis. Two reviewers independently reviewed the eligibility of the studies and abstracted data (sample population; characteristics of FDG-PET; and the number of true-positive results, true-negative results, false-positive results, and false-negative results). The authors estimated the pooled sensitivity, false-positive rate, and maximum joint sensitivity and specificity.

RESULTS

Twenty studies were eligible for the metaanalysis. Fourteen studies included patient-based data, comprising a sample size of 854 subjects, and 7 studies included lesion-based data, totaling 3658 lesions. Among those studies with patient-based data, the median sensitivity was 90.3% and the median specificity was 91.1%. The pooled sensitivity was 90.9% (95% confidence interval [95% CI], 88.0-93.4) and the pooled false-positive rate was 10.3% (95% CI, 7.4-13.8). The maximum joint sensitivity and specificity was 87.8% (95% CI, 85.0-90.7). The pooled sensitivity and false-positive rate appeared to be higher in patients with Hodgkin disease compared with those with non-Hodgkin lymphoma.

CONCLUSIONS

The results of the current study indicate that FDG-PET is a valuable tool for the staging and restaging of patients with lymphoma; showing a high positivity and specifity. Clinicians may consider adding FDG-PET to the staging workup of patients with lymphoma.

Endoprobe: A system for radionuclide-guided endoscopy

Methods to guide the surgical treatment of cancer utilizing handheld beta-sensitive probes in conjunction with tumor-avid radiopharmaceuticals [such as 18F-fluorodeoxyglucose (FDG)] have previously been developed. These technologies could also potentially be used to assist in minimally invasive techniques for the diagnosis of cancer. The goal of this project is to develop and test a system for performing radionuclide-guided endoscopies. This system (called Endoprobe) has four major subsystems: beta detector, position tracker, endoscope, and user interface. The beta detection unit utilizes two miniaturized solid state detectors to preferentially detect beta particles. The position tracking system allows real-time monitoring of the unit's location. The beta detector and position tracking system's receiver are mounted on the tip of an endoscope. Information from the beta detector and tracking system, in addition to the video signal from the endoscope, are combined and presented to the user via a computer interface. The system was tested in a simulated search for radiotracer-avid areas of esophageal cancer. The search for esophageal cancer was chosen because this type of cancer is often diagnosed with endoscopic procedures and has been reported to have good affinity for FDG. Accumulations of FDG in the normal organs of the abdomen were simulated by an anthropomorphic torso phantom filled with the appropriate amounts of radioactivity. A 1.5- mm-thick gelatin film containing FDG was used to simulate radiotracer uptake in the lining of normal esophagus. Esophageal lesions (both benign and malignant) were simulated by thin disks of gelatin (diameters=3.5-12 mm) containing appropriate concentrations of FDG embedded in the gelatin film simulating normal esophagus. Endoprobe facilitated visual identification and examination of the simulated lesions. The position tracking system permitted the location of the Endoprobe tip to be monitored and plotted in real time on a previously acquired positron emission tomography-computed tomography (PET-CT) image of the phantom. The detection system successfully acquired estimates of the beta flux emitted from areas chosen by the user. Indeed, Endoprobe was able to assist in distinguishing simulated FDG-avid areas as small as 3.5 mm in diameter from normal esophagus (p value <0.025). In addition to FDG, Endoprobe can be used with other positron or electron-emitting radionuclides such as IC or 131I. The next phase of this project will focus on modification of the prototype to make it more suitable for clinical use.

FDG PET for imaging pericardial manifestations of Hodgkin lymphoma

A 61-year-old man with Hodgkin lymphoma (mixed type), with lymph node manifestations and extranodal and bone marrow involvement in both supra- and infradiaphragmatic locations (stage 4), had dyspnea and tachycardia on echocardiography. There were pleural and pericardial effusions and thickening of the epicardium and pericardium. These findings and computed tomographic findings were suspicious for manifestations of Hodgkin lymphoma. The pericardial findings were demonstrated on F-18 fluorodeoxyglucose positron emission tomographic imaging.

Impact of technology on the utilisation of positron emission tomography in lymphoma: current and future perspectives

Positron emission tomography (PET) has now gained a place in the management of patients with cancer, including those with Hodgkin's disease and non-Hodgkin's lymphoma. Restaging studies and those addressing the monitoring of response to treatment are especially in focus. Most of the knowledge gained has been achieved with dedicated BGO-based PET technology, but there are a number of developments that will impact on the use of this metabolic imaging technique in the investigation of patients with lymphoma. The challenges ahead are determined by the need for high-quality whole-body imaging associated with increased patient throughput and the need to investigate the role of new labelled ligands. The latter are likely to yield new insights into tumour cell characterisation, tumour behaviour and tumour outcome assessment. The study of new radiolabelled ligands will impose further demands for rapid dynamic data acquisition and accurate tracer quantification. Current and future developments in PET technology range from the use of new detector materials to different detector geometries and data acquisition modes. The search for alternatives to BGO scintillation materials for PET has led to the development of PET instruments utilising new crystals such as LSO and GSO. The use of these new detectors and the increased sensitivity achieved with 3D data acquisitions represent the most significant current developments in the field. With the increasing demands imposed on the clinical utilisation of PET, issues such as study cost and patient throughput will emerge as significant future factors. As a consequence, low-cost units are being offered by the manufacturers through the utilisation of gamma camera-based SPET systems for PET coincidence imaging. Unfortunately, clinical studies in lymphoma and other cancers have already demonstrated the limitations of this technology, with 20% of lesions <15 mm in size escaping detection. On the other hand, the recent development of combined PET/CT devices attempts to address the lack of anatomical information inherent with PET images, taking advantage of further improvement in patient throughput and hence cost-effectiveness. Preliminary studies using this multimodality imaging approach have already demonstrated the potential of the technique. Although the potential exists, certain technical issues with PET/CT require refinement of the methodology. Such issues include organ movement (such as respiratory motion), which strongly influences the image fusion of a rapidly acquired CT scan with the slower acquisition of a PET dataset, and the derivation of CT-based attenuation coefficients in the presence of contrast agents or metallic implants. The application of the technology for radiotherapy planning also poses a number of associated challenges. Finally, the development of dedicated PET systems based on planar detector arrangements with new detector components has the potential to improve clinical throughput by over 100%, but clinical trials using such systems have still to be carried out in order to establish the associated whole-body image quality.

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.

Role of video-laparoscopy in the staging of intra-abdominal lymphomas and gastrointestinal cancer

There is good category II/III evidence that video-laparoscopic staging is valuable in certain gastrointestinal (gastric, esophageal, pancreatic, and hepatobiliary) and intra-abdominal lymphomas, but no category I evidence (based on prospective randomized trials). The evidence available is all retrospective, but of sufficient consistency to indicate that laparoscopic staging adds to the primary (imaging) staging and often alters the clinical stage of the disease and hence the management of the individual patient. The advent of laparoscopic contact ultrasound (LCU) scanning has improved the staging accuracy for pancreatic and hepatobiliary neoplasms. The laparoscopic approach also offers a means of surgical palliation in certain patient groups. However, there are a number of unresolved issues concerning the use of video-laparoscopy. The most important concerns whether staging laparoscopy should be performed immediately before scheduled surgery or as a separate intervention. The cost-efficacy of these two management options needs to be evaluated in prospective studies. In some centres, laparoscopic staging is being conducted by gastroenterologists and hepatologists. This raises issues of safety and ability to undertake certain procedures that may be necessary during the laparoscopic staging.