Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) for the staging of low-grade non-Hodgkin's lymphoma (NHL)

PET in lymphoma

This review attempts to discuss the role of positron emission tomography (PET) imaging for staging, treatment response and follow-up of patients with lymphoma. The pitfalls and impact of PET imaging on the clinical management are also addressed.

Role of fluorine-18 fluoro-deoxyglucose positron emission tomography scan in the evaluation and follow-up of patients with low-grade lymphomas

BACKGROUND

Fluorine-18 fluoro-deoxyglucose positron emission tomography (FDG-PET) scanning has excellent sensitivity and specificity for staging non-Hodgkin lymphomas, but to the authors' knowledge few studies to date have evaluated FDG-PET in low-grade lymphomas only.

METHODS

A retrospective study was performed on patients with biopsy-proven nontransformed and transformed follicular lymphoma (FL), B-cell small-cell lymphocytic lymphoma (SLL/CLL), or marginal zone lymphoma (MZL) who underwent PET and computed tomography (CT) scans within 3 weeks. Standard uptake values (SUV) of all abnormal foci were measured.

RESULTS

In FL, PET demonstrated 94% sensitivity and 100% specificity for staging. PET was more specific than CT for detecting recurrence or assessing therapeutic responses (91% vs. 50%). FDG avidity among patients with WHO Grades 1, 2, and 3 disease was not significantly different (analysis of variance [ANOVA]). For MZL staging, PET had moderate sensitivity (71%) and outperformed CT alone in the depiction of extranodal sites (85% vs. 57% sensitivity). In SLL/CLL, PET sensitivity was 53% and underestimated disease extent in 5 of 19 patients (26%) compared with CT. PET did not affect initial management but confirmed suspected recurrences in 75% of patients. Nontransformed FL had a higher SUV (ANOVA, P < .05) compared with MZL and SLL/CLL. SUV was higher in transformed than in nontransformed tumors (P < .001, Student t test).

CONCLUSIONS

PET usefulness in staging low-grade lymphomas varies depending on histology. PET sensitivity is excellent in FL and moderate in MZL. PET is more specific than CT for follow-up in all types. PET has limited usefulness for SLL/CLL staging. However, a suggestive pattern of hazy and mild uptake was often noted in positive scans. In all low-grade lymphomas, the emergence of foci of intense uptake should raise suspicion of conversion to high-grade disease.

18F-fluoro-deoxy-glucose positron emission tomography (18F-FDG-PET) visualizes follicular lymphoma irrespective of grading

BACKGROUND

18F-fluoro-deoxy-glucose positron emission tomography (18F-FDG-PET) has become a routine measure for staging and follow-up of patients with aggressive lymphoma. By contrast, its usefulness to visualize indolent lymphomas characterized by a lower cellular turnover has not clearly been defined. We have investigated accuracy and clinical usefulness of 18F-FDG-PET in patients with follicular lymphoma (FL).

PATIENTS AND METHODS

A total of 64 patients with FL WHO grade I - III (48, 5, and 11 patients) were imaged at our institution to assess the value of 18F-FDG-PET for imaging of FL of different gradings. A total of 115 scans (48 before therapy and 67 for response assessment after treatment) were performed, and findings were compared to conventional staging including CT-scan of thorax and abdomen, sonography of lymph nodes and bone marrow biopsy.

RESULTS

Overall, 18F-FDG-PET had a sensitivity of 98%, a specificity of 94%, a positive predictive value of 95% and a negative predictive value of 98%. These results were significantly more accurate (P = 0.023) than the conventional radiology studies. There was no significant difference (P = 0.093) in the accuracy between patients with indolent (WHO grade I and II) versus aggressive FL (WHO grade III).

CONCLUSION

18F-FDG-PET scan is a reliable method for staging and follow up of patients with nodal FL irrespective of tumor grading.

Can [18F]fluorodeoxyglucose positron emission tomography imaging complement biopsy results from the iliac crest for the detection of bone marrow involvement in patients with malignant lymphoma?

OBJECTIVES

To assess the usefulness of [18F]fluorodeoxyglucose positron emission tomography in the detection of bone marrow involvement in malignant lymphoma, and its impact in clinical management.

METHODS

One hundred and six consecutive patients with a confirmed diagnosis of lymphoma, referred for staging or restaging of Hodgkin's lymphoma (n=18) or non-Hodgkin's lymphoma (n=88), were reviewed retrospectively. A positron emission tomography scan and bone marrow biopsy of the iliac crest were performed in all patients. The assessment of bone marrow involvement by lymphoma was confirmed by histology and/or progression of bone marrow lesions in clinical follow-up.

RESULTS

In 28 of 106 patients, bone marrow involvement was found. Positron emission tomography was more sensitive (86%) than bone marrow biopsy (57%). Positron emission tomography and bone marrow biopsy were concordant by positive correlation in 12 of 28 cases (43%) and by negative correlation in 77 of 78 cases (99%). Ten cases of non-Hodgkin's lymphoma and two cases of Hodgkin's lymphoma with positive positron emission tomography results and an initial negative bone marrow biopsy showed clinical progression of the bone marrow lesions and/or subsequent positive histology. These were considered as false-negative results for bone marrow biopsy. In seven of the 12 positive cases with negative bone marrow biopsy, positron emission tomography uptake distant from the site of the biopsy was seen. In four cases of follicular lymphoma, the bone marrow biopsy was positive and the positron emission tomography scan was normal.

CONCLUSIONS

Positron emission tomography and bone marrow biopsy are complementary in assessing the presence of bone marrow involvement in patients with malignant lymphoma. In our series, positron emission tomography was more sensitive than bone marrow biopsy in Hodgkin's and non-Hodgkin's lymphoma, except in follicular lymphoma.

Impact of CT and 18F-deoxyglucose positron emission tomography image fusion for conformal radiotherapy in esophageal carcinoma

PURPOSE

To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiotherapy planning for esophageal carcinoma patients.

METHODS AND MATERIALS

Thirty-four esophageal carcinoma patients were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same treatment position. PET images were coregistered using five fiducial markers. Target delineation was initially performed on CT images, and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume.

RESULTS

(18)F-fluorodeoxy-D-glucose-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative conformal radiotherapy. The gross tumor volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and increased in 7 patients (21%). The GTV reduction was > or =25% in 4 patients owing to a reduction in the length of the esophageal tumor. The GTV increase was > or =25% with FDG-PET in 2 patients owing to the detection of occult mediastinal lymph node involvement in 1 patient and an increased length of the esophageal tumor in 1 patient. Modifications of the GTV affected the planning treatment volume in 18 patients. Modifications of the delineation of the GTV and displacement of the isocenter of the planning treatment volume by FDG-PET also affected the percentage of total lung volume receiving >20 Gy in 25 patients (74%), with a dose reduction in 12 patients and dose increase in 13.

CONCLUSION

In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of esophageal carcinoma. The affect on treatment outcome remains to be demonstrated.

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.

A Comparison of Whole-Body MRI and CT for the Staging of Lymphoma

OBJECTIVE

Our objective was to compare whole-body MRI and CT for the staging of lymphoma.

CONCLUSION

Whole-body MRI represents an alternative to CT in the staging of lymphoma, with an ability to stage disease, identify lymph nodes greater than 1.2 cm, and the additional ability to evaluate for the presence or absence of disease spread to bone marrow. CT allows detection of more nodes (< 1.2 cm) than MRI but this does not alter tumor stage.

Evaluation of Therapy for Lymphoma

Positron emission tomography (PET) using (18)F-fluorodeoxyglucose ((18)F-FDG) is the best noninvasive imaging technique for to assess response in patients suffering from lymphoma. Early response evaluation ("interim PET") after one, a few cycles, or at midtreatment can predict response, progression-free survival, and overall survival. We calculated from data of 7 studies an overall sensitivity to predict treatment failure of 79%, a specificity of 92%, a positive predictive value (PPV) of 90%, a negative predictive value (NPV) of 81%, and an accuracy of 85%. Although it is not yet indicated to change patient management based on residual (18)F-FDG uptake on interim scan in chemotherapy-sensitive patients, prospective studies evaluating the role of an interim PET in patient management clearly are warranted. (18)F-FDG PET also has an important prognostic role in relapsing patients after reinduction chemotherapy before high-dose chemotherapy (HCT) followed by autologous stem cell transplantation (ASCT). However, all chemotherapy-sensitive patients remain candidates for HCT followed by ASCT, even if (18)F-FDG PET showed residual (18)F-FDG uptake. We calculated from data of 3 studies an overestimated risk of relapse in 16% of all PET-positive patients. Some patients with residual (18)F-FDG uptake will have a good outcome after HCT followed by ASCT. (18)F-FDG PET is the imaging technique of choice for end-of-treatment evaluation. However, (18)F-FDG is not specific for tumoral tissue. Active inflammatory lesions and infectious processes can be falsely interpreted as malignant residual cells. However, a negative (18)F-FDG PET cannot exclude minimal residual disease. Consequently, it is always indicated to correlate PET findings with clinical data, other imaging modalities, and/or a biopsy. We calculated, from data of 17 studies in end-of-treatment evaluation, a sensitivity of 76%, a specificity of 94%, a PPV of 82%, a NPV 92%, and an accuracy of 89%.

Initial Staging of Lymphoma With Positron Emission Tomography and Computed Tomography

Lymphomas represent a diverse range of diseases with manifold presentations, outlook, and therapeutic approaches. Key to the modern management of lymphoma is accurate delineation of the extent of disease. The inability of computed tomography (CT) to identify the involvement of nonenlarged nodes and its relatively poor sensitivity in the detection of extra-nodal sites of involvement limit the performance of noninvasive staging techniques. Functional imaging techniques such as Ga-67 scintigraphy have been used for many years to improve the evaluation of patients with lymphoma. While providing complementary information to CT in many clinical settings, functional imaging has never had sufficient accuracy or localizing ability to seriously challenge conventional primary staging paradigms. (18)F-Fluorodeoxyglucose positron emission tomography (FDG PET), however, has been demonstrated to have both higher sensitivity and specificity than CT in many comparative series. Now that this technology also can be performed at the same time as structural imaging in the form of hybrid PET/CT devices, clinicians are rethinking the methods used to select, plan, and monitor therapy of lymphoma patients. In our institution, FDG PET/CT has become the preferred initial staging tool for patients with lymphoma.

Computed tomography and 18F-FDG positron emission tomography for therapy control of Hodgkin's and non-Hodgkin's lymphoma patients: when do we really need FDG-PET?

BACKGROUND

The aim of this study was to evaluate the accuracy of computed tomography (CT) and [(18)F]fluoro-deoxy-d-glucose positron emission tomography (FDG-PET) for prediction of progression-free survival of Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL) patients after completion of therapy.

PATIENTS AND METHODS

CT and FDG-PET were performed in 40 HD, 17 indolent NHL and 44 aggressive NHL patients (29 women, 72 men; aged 41+/-14 years) in a median of 2 months after therapy. Progression-free survival was evaluated using the Kaplan-Meier method. Independent prognostic factors were identified by means of Cox proportional hazards model.

RESULTS

CT imaging results were progressive disease (PD) in five, stable disease (SD) in 57, and partial response (PR) or complete remission (CR) in 39 patients. FDG-PET suggested residual lymphoma in 24 patients. Three-year progression-free survival rates after exclusion of five PD patients were: 100% (PET negative; CT: PR or CR), 81% (PET negative; CT: SD), 21% (PET positive; CT: SD) and 0% (PET positive; CT: PR). FDG-PET (P<0.0001) and bulky disease (P <0.05) were identified as independent prognostic variables.

CONCLUSIONS

Among lymphoma patients with PR and SD on CT, FDG-PET discriminated those destined to progress into a low risk of < or =20% and a high risk for recurrence of > or =80%.

Tomographie par émission de positons et fusion d'images de simulation virtuelle par tomodensitométrie. Impact sur la planification de la radiothérapie conformationnelle des cancers de l'œsophage

PURPOSE

To study the impact of fused (18)F-fluoro-deoxy-D-glucose (FDG)-hybrid positron emission tomography (PET) and computed tomography (CT) images on conformal radiation therapy (CRT) planning for patients with esophageal carcinoma.

PATIENTS AND METHODS

Thirty-four patients with esophageal carcinoma were referred for concomitant radiotherapy and chemotherapy with radical intent. Each patient underwent CT and FDG-hybrid PET for simulation treatment in the same radiation treatment position. PET-images were coregistered using five fiducial markers. Target delineation was initially performed on CT images and the corresponding PET data were subsequently used as an overlay to CT data to define the target volume.

RESULTS

FDG-PET identified previously undetected distant metastatic disease in 2 patients, making them ineligible for curative CRT. The Gross Tumor Volume (GTV) was decreased by CT and FDG image fusion in 12 patients (35%) and was increased in 7 patients (20.5%). The GTV reduction was >or=25% in 4 patients due to reduction of the length of the esophageal tumor. The GTV increase was >or=25% with FDG-PET in 2 patients due to the detection of occult mediastinal lymph node involvement in one patient and an increased length of the esophageal tumor in the other patient. Modifications of the GTV affected the planning treatment volume (PTV) in 18 patients. Modifications of delineation of GTV and displacement of the isocenter of PTV by FDG-PET also affected the percentage of total lung volume receiving more than 20 Gy (VL20) in 25 patients (74%), with a dose reduction in 12 patients and a dose increase in 13 patients.

CONCLUSION

In our study, CT and FDG-PET image fusion appeared to have an impact on treatment planning and management of patients with esophageal carcinoma related to modifications of GTV. The impact on treatment outcome remains to be demonstrated.

Contribution of PET imaging to the initial staging and prognosis of patients with Hodgkin's disease

BACKGROUND

Positron emission tomographic (PET) scanning utilizing [18F]fluorodeoxyglucose (FDG) is a new method of tumor imaging based on the increased glucose metabolic activity of malignant tumors. In Hodgkin's disease (HD), PET has proven value for the evaluation of residual masses following treatment and for the early diagnosis of relapse. In the initial staging of HD, PET frequently shows a higher stage than conventional methods (upstaging by PET). In the present study, we evaluated the frequency of stage changes by PET in a multicenter setting and determined its prognostic relevance.

PATIENTS AND METHODS

A total of 73 patients with newly diagnosed HD were staged with both conventional methods and whole-body PET scanning. All histological types and stages were represented. The median time of follow-up after the initial diagnosis was 25 months (range 1 month to 5 years). The response to treatment was determined by standard clinical and diagnostic criteria. For the purpose of this analysis, data from a PET center associated with a university medical center and a PET center associated with a group oncology practice were combined.

RESULTS

A total of 21 patients (28.8%) were upstaged by PET compared with conventional methods. In two cases (2.7%), a lower stage was suggested by PET scanning. With one possible exception, the upstaging had no obvious clinical or biological correlate. Among 12 patients in stage I (A + B) by conventional methods, seven were upstaged by PET (58.3%), four to stage II, one to stage III and two to stage IV. Among 42 patients in stage II, eight were upstaged by PET (19.0%), six to stage III and two to stage IV. Among 12 patients in stage III, six (50%) were upstaged to stage IV by PET. If only early-stage patients and major changes are considered (stages IA-IIB to III or IV), among 49, 10 were upstaged to III or IV, whereas in 39 staging was unchanged following PET. In the former group, three relapsed or were refractory compared with none in the latter group (P<0.006). In advanced stage patients (IIIA or IIIB) a trend toward treatment failure was apparent in patients who were upstaged by PET.

CONCLUSIONS

PET scanning is an interesting new modality for the accurate staging of patients with HD and frequently shows a higher stage than conventional methods. PET should be performed at initial diagnosis and should be included in prospective studies of patients with HD. Upstaging by PET may represent a risk factor for a more advanced stage or a biologically more aggressive tumor. Patients with early-stage disease as identified by conventional methods have a significant risk of treatment failure if a more advanced stage is indicated by PET. At present, major stage changes suggested by PET imaging should be confirmed by an independent diagnostic method.

Intensity of 18fluorodeoxyglucose uptake in positron emission tomography distinguishes between indolent and aggressive non-Hodgkin's lymphoma

PURPOSE

(18)Fluorodeoxyglucose positron emission tomography (FDG PET) is widely used for the staging of lymphoma. We investigated whether the intensity of tumor FDG uptake could differentiate between indolent and aggressive disease.

MATERIALS AND METHODS

PET studies of 97 patients with non-Hodgkin's lymphoma who were untreated or had relapsed and/or persistent disease and had not received treatment within the last 6 months were analyzed, and the highest standardized uptake value (SUV) per study was recorded. Correlations were made with histopathology.

RESULTS

FDG uptake was lower in indolent than in aggressive lymphoma for patients with new (SUV, 7.0 +/- 3.1 v 19.6 +/- 9.3; P < .01) and relapsed (SUV, 6.3 +/- 2.7 v 18.1 +/- 10.9; P = .04) disease. Despite overlap between indolent and aggressive disease in the low SUV range (indolent, 2.3 to 13.0; aggressive, 3.2 to 43.0), all cases of indolent lymphoma had an SUV <or= 13. A receiver operating characteristic (ROC) analysis demonstrated that the SUV distinguished reasonably well between aggressive and indolent disease (area under ROC curve, 84.7%), and an SUV > 10 excluded indolent lymphoma with a specificity of 81%. With a higher cutoff for the SUV, the specificity would have been higher.

CONCLUSION

FDG uptake is lower in indolent than in aggressive lymphoma. Patients with NHL and SUV > 10 have a high likelihood for aggressive disease. This information may be helpful if there is discordance between biopsy and clinical behavior.

FDG-PET scanning for detection and staging of extranodal marginal zone lymphomas of the MALT type: a report of 42 cases

BACKGROUND

Although reports have suggested that FDG-PET scans were not useful for staging of extranodal marginal zone lymphomas (MZL), experience at our center suggests otherwise. Thus we reviewed the findings of FDG-PET scans in patients with extranodal MZL seen at our center.

PATIENTS AND METHODS

A database of 175 patients with histologically-confirmed diagnoses of extranodal MZL was reviewed. Forty-two patients who had had FDG-PET scans for initial staging were identified. All information was obtained by retrospective review of medical records and PET scans.

RESULTS

Thirty-four (81%) patients had focal tracer uptake within verified tumor sites, six (14%) patients did not, and two (5%) patients had indeterminate uptake. Seven of the 34 (21%) patients with uptake within verified tumor sites had uptake in regional lymph nodes and four patients were upstaged due to FDG-PET findings. Eight patients also obtained post-treatment FDG-PET scans. In five of those eight, the repeated FDG-PET scan indicated a complete response, and in three there was an indeterminate or mixed response.

CONCLUSION

FDG-PET scans carried out for initial staging of extranodal MZL detected disease in a high proportion of patients. This study suggests that imaging with FDG-PET scans is useful for both initial staging and follow-up of patients with extranodal MZL.

FDG PET in the Evaluation of Treatment for Lymphoma: Clinical Usefulness and Pitfalls

Positron emission tomography (PET) with 2-[fluorine-18] fluoro-2-deoxy-d-glucose (FDG) may play an important role in the evaluation and management of malignant lymphoma. FDG uptake is predictive of therapeutic response during the course of treatment. After completion of chemotherapy, residual abnormalities representing either residual tumor or necrotic or fibrotic tissue are not uncommon, and FDG PET may be more accurate than computed tomography (CT) or magnetic resonance imaging in assessing residual disease and identifying patients who require more intense treatment. However, posttreatment FDG PET does not help exclude the presence of minimal residual disease, which may lead to disease relapse. Furthermore, FDG is not a tumor-specific substance, and increased accumulation may be seen in a variety of benign entities and scenarios (eg, infection, drug toxicity, granulocyte colony-stimulating factor therapy, radiation therapy, physiologic activity, postoperative or postbiopsy changes, fracture, degenerative change, injection leakage), which may yield false-positive findings. Nevertheless, recognition of these entities and correlation of FDG PET findings with clinical and other radiologic findings-especially those at combined PET and CT or PET-CT fusion imaging-allows improved diagnostic accuracy. If the interpretation of positive findings is exceptionally difficult, short-term follow-up may be helpful.

Utility of fluorodeoxyglucose-PET imaging in the management of patients with Hodgkin's and non-Hodgkin's lymphomas

FDG-PET imaging has a number of advantages in the management of patients with lymphoma. PET shows a functional metabolic status and gives quantitative information. In addition, PET provides whole-body images that give a comprehensive assessment of disease extent during the staging and followup. Based on the present literature, FDG-PET is at least equivalent to CT for the initial staging of lymphomas. The impact of new technologies of combined PET/CT and fast-scanning CT with contrast has yet to be evaluated in the management of lymphoma patients, however. At this point, FDG-PET and CT must be considered as giving complementary staging information. FDG-PET also has high diagnostic accuracy for restaging lymphoma after initial treatment. FDG-PET has shown high accuracy in the early prediction of response to chemotherapy and in the evaluation of residual masses after chemotherapy or radiation therapy. Therefore, PET is likely to play a major role in tailoring the intensity of the treatment to the individual patient. A pretreatment FDG-PET study is essential for accurate assessment of residual masses and early monitoring of response to the treatment. In addition, a baseline PET scan will help detect relapse or residual disease, because relapse occurs most often in the region of previous disease.

Diagnostic value and limitations of fluorine-18 fluorodeoxyglucose positron emission tomography for cartilaginous tumors of bone

BACKGROUND

A variety of imaging modalities are currently used for the preoperative evaluation of cartilage tumors. Although the anatomic details of the lesions are demonstrated well on computerized tomography and magnetic resonance images, those studies yield little information about the biologic activity of the tumors. In this study, we investigated the glucose metabolism of cartilage tumors measured by positron emission tomography and its correlation with histopathologic grades.

METHODS

Thirty-five biopsy-proven cartilaginous tumors in twenty-seven patients were studied with plain radiographs, bone-scanning, magnetic resonance imaging, and positron emission tomography. The glucose metabolism in these cartilaginous tumors was measured quantitatively by calculating the maximal standardized uptake value of the region of interest. This value was then correlated with histopathologic grade, tumor size, recurrence, and metastasis.

RESULTS

There were thirteen benign bone tumors, twelve grade-I chondrosarcomas, and ten high-grade (grade-II or III) chondrosarcomas. The mean maximal standard uptake values were 1.147 +/- 0.751 in the benign tumors, 0.898 +/- 0.908 in the grade-I chondrosarcomas, and 6.903 +/- 5.581 in the high-grade chondrosarcomas. There was no significant difference in these values between the benign cartilage tumors and the grade-I chondrosarcomas (p > 0.05). However, there was a significant difference between the low-grade (benign and grade-I) and high-grade chondrosarcomas (p = 0.009). Metastasis, but not tumor size or recurrence, was associated with a higher standard uptake value (p = 0.031). Two large pelvic grade-I chondrosarcomas demonstrated no radioisotope uptake on bone-scanning or on positron emission tomography. Positron emission tomography demonstrated grade-II and III metastatic lesions in the lung and other anatomic locations. When the cutoff for the standardized uptake value was set at 2.3 for grade-II or III chondrosarcomas, the positive predictive value was 0.82 (95% confidence interval, 0.48 to 0.97) and the negative predictive value was 0.96 (95% confidence interval, 0.77 to 1.00).

CONCLUSIONS

Grade-II and III chondrosarcomas have a higher glucose metabolism than do low-grade cartilage tumors. However, the measurement of glucose metabolism by positron emission tomography alone cannot distinguish between benign and grade-I malignant cartilaginous tumors. It is important to understand the advantages and disadvantages of imaging modalities for accurate interpretation of results. Although positron emission tomography has limitations, it may be useful for predicting high-grade chondrosarcomas.

LEVEL OF EVIDENCE

Diagnostic study, Level II-1 (development of diagnostic criteria on basis of consecutive patients [with universally applied reference "gold" standard]). See Instructions to Authors for a complete description of levels of evidence.

The role of PET imaging in lymphoma

Positron emission tomography using fluorine-18 (FDG-PET) is increasingly used in the staging and follow-up of malignant lymphomas, although its precise role has not yet been determined. This review considers the results reported at the different stages in the disease history and separately considers the major histological subtypes. Attention is given to the situations in which PET scanning is most likely to influence management. Finally, this review discusses ongoing developments in PET scanning with improved resolution and different radiolabelled tracers.

Positron emission tomography in the evaluation of lymphoma

Positron emission tomography (PET) using (18)F-fluoro-deoxyglucose (FDG) has emerged in recent years as an important tool for the evaluation of lymphoma patients during their course of disease. At diagnosis, FDG imaging is capable of detecting nodal and extra nodal sites of disease and provides accurate staging. FDG-PET is superior to computed tomography, during and at the end of first-line treatment or salvage therapeutic regimens, as a tool for monitoring therapeutic response. PET enables the differential diagnosis of residual viable tumor versus a remnant fibrotic or necrotic mass. PET also provides prognostic data of high clinical significance for both Hodgkin's disease and non-Hodgkin's lymphoma. Results of this metabolic imaging modality, interpreted in view of the pretherapy risk profile of the individual patient, are predictive of the immediate success of a certain therapeutic strategy, as well as of overall and disease-free survival. PET appears to play also an important role in the detection of lymphoma relapse. Data comparing (67)Gallium scintigraphy and FDG-PET indicate the latter as the functional imaging modality of choice for assessment of lymphoma patients. Preliminary studies show an additional value of fused PET/computed tomography imaging for further improved diagnosis, staging and definition of status of lymphoma.

Enhanced Marrow [18F]Fluorodeoxyglucose Uptake Related to Myeloid Hyperplasia in Hodgkin's Lymphoma Can Simulate Lymphoma Involvement in Marrow

[18F]Fluorodeoxyglucose (FDG) positron emission tomography (PET) is increasingly used for the clinical staging of lymphomas and for assessment of response to therapy. We report the case of a woman with classic Hodgkin's lymphoma who had marked FDG uptake by tumor and bone marrow suggestive of diffuse marrow involvement by lymphoma. However, iliac crest bone marrow examination showed marked myeloid hyperplasia without evidence of lymphoma involvement. We discuss the implications for interpretation of FDG-PET imaging of bone marrow in lymphomas.

Clinical applications of PET in oncology

Positron emission tomography (PET) provides metabolic information that has been documented to be useful in patient care. The properties of positron decay permit accurate imaging of the distribution of positron-emitting radiopharmaceuticals. The wide array of positron-emitting radiopharmaceuticals has been used to characterize multiple physiologic and pathologic states. PET is used for characterizing brain disorders such as Alzheimer disease and epilepsy and cardiac disorders such as coronary artery disease and myocardial viability. The neurologic and cardiac applications of PET are not covered in this review. The major utilization of PET clinically is in oncology and consists of imaging the distribution of fluorine 18 fluorodeoxyglucose (FDG). FDG, an analogue of glucose, accumulates in most tumors in a greater amount than it does in normal tissue. FDG PET is being used in diagnosis and follow-up of several malignancies, and the list of articles supporting its use continues to grow. In this review, the physics and instrumentation aspects of PET are described. Many of the clinical applications in oncology are mature and readily covered by third-party payers. Other applications are being used clinically but have not been as carefully evaluated in the literature, and these applications may not be covered by third-party payers. The developing applications of PET are included in this review.

The use of positron emission tomography with [18F] 2-fluoro-D-2-deoxyglucose (FDG-PET) in Hodgkin and non-Hodgkin's lymphoma

Positron emission tomography (PET) has obtained a place in the management of patients with hematologic disease particularly those with lymphoproliferative disorders. In the staging and monitoring of cancer, the use of PET in combination with fluorine-18 fluorodeoxyglucose (FDG) has already demonstrated its benefit when compared with conventional imaging modalities. One such area which has already profited from the use of PET is Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). Computed tomography and magnetic resonance imaging are equivalent in staging and monitoring disease, while gallium-67 imaging is more useful in HD and high grade NHL for studies of response to therapy.Paul et al. in 1987 were the first to describe PET imaging in patients with lymphoma; since this time a number of studies have demonstrated that PET technique is superior to 67 Ga imaging in staging lymphoma before therapy and is useful in the evaluation and the prediction of relapse after high dose therapy with stem cell transplantation.PET is based on the utilisation of positron emitting radiopharmaceuticals and the detection in coincidence of the two nearly collinear 511-keV photons emitted following positron annihilation with an electron in vivo. By surrounding the patients with detectors, a large number of acquired coincident events can lead to the construction of an image of the in vivo radioisotope distribution.

Thallium-201-chloride scintigraphy in staging and monitoring radiotherapy response in follicular lymphoma patients

PURPOSE

To study thallium-201-chloride scintigraphy (201Tl-S) in staging and monitoring response after radiotherapy in follicular lymphoma (FL) patients.

PATIENTS AND METHODS

Forty-one consecutive and unselected FL patients were examined by 'Conventional Standard Staging' (CSS) procedures (history and physical examination, ultrasound, CT scans, biopsies and fine needle aspiration cytology) prior to irradiation. Eight standardized potentially affected lymphoma localizations (neck, axilla, mediastinum, spleen, paraaortic, parailiac, femoral and extranodal) per patient were separately studied, resulting in the investigation of 328 localizations. Thirty minutes after the intravenous administration of a tracer dose of 150 MBq thallium-201-chloride total body images were made, immediately followed by single photon emission computed tomography acquisition. All lymphoma localizations were subsequently irradiated. Patients were re-examined after a median of 4 weeks (range 3-6 weeks) by all CSS modalities and 201Tl-S. Diagnostic performance was evaluated both per site and per patient, both in the diagnostic phase of the study as well as in the post-treatment re-evaluation phase.

RESULTS

In staging, 201Tl-S was positive in 82 of the 129 initial positive regions by CSS (64%). This percentage increased to 70% when eliminating upper abdominal lymph nodes from the analysis. In 24 patients all lesions were visualized by 201Tl-S, in 11 patients some but not all lesions were detected. In six patients none of the lesions were detected by 201Tl-S. In four patients, four additional lesions were initially found by 201Tl-S only. After irradiation, 83 of the total 86 positive regions reached a complete or partial remission by CSS. Eighty-one of these were also diagnosed as remission by 201Tl-S and two as stable disease. In 31 out of 35 patients (89%; 95% CI: 73-97%) the overall response in all irradiated sites was identical by 201Tl-S and CSS. Only two patients, in remission on CSS modalities, showed stable disease on 201Tl-S, while two others were diagnosed as CR by CSS and PR by 201Tl-S.

CONCLUSIONS

201Tl-S has limited additional value in staging FL patients, since only two-thirds of all localizations are detected. However, 201Tl-S is accurate in monitoring radiation treatment response in FL patients. If an FL patient with a positive 201Tl-S at diagnosis is treated by irradiation, the treatment response can be reliably ascertained by only performing a 201Tl-S.

PET Scans in the Staging of Lymphoma: Current Status

Positron emission tomography (PET) is a novel functional imaging technique that provides several inherent advantages over conventional nuclear scintigraphy. Several studies have suggested a role for PET using the positron emitter fluorine-18 in the diagnosis and follow-up of patients with lymphoma. This review summarizes the existing data evaluating the role of 2-fluoro-2-deoxy-D-glucose (FDG)-PET in both the staging and follow-up of patients with lymphoma. Most studies of PET involve patients with either Hodgkin's disease or diffuse large B-cell non-Hodgkin's lymphoma. PET detects more disease sites above and below the diaphragm on staging of lymphoma than gallium scintigraphy and may have particular utility in the evaluation of the spleen. Moreover, persistently positive PET scans during and after chemotherapy appear to have a high sensitivity for predicting subsequent relapse. A negative PET scan at the end of therapy provides very favorable prognostic information. Persistently positive PET scans at the end of therapy warrant close follow-up or additional diagnostic procedures, since some of those patients may remain in prolonged remission. Clearly, additional studies, including prospective blinded trials and cost-effectiveness analyses, are warranted to determine which subsets of patients with lymphoma ultimately will benefit from this modality.

PET scan imaging in oncology

With the emergence of positron emission tomography (PET) from research laboratories into routine clinical use, it is important to redefine the most appropriate use of each imaging technique. The aim of this review article is to show the potential of PET in oncology. We discuss the most promising indications and the perspectives for the future. We will also point out the shortcomings and the important questions to be answered before fully considering PET as a necessary tool in the day-to-day practice of oncology. Although many studies have documented the high accuracy of 18F-FDG PET for the detection and staging of malignant tumours and for the monitoring of therapy results in these patients, it is very important to assess the impact of the technique on patient outcome and to show cost-effectiveness from the societal viewpoint.

PET for staging of Hodgkin's disease and non-Hodgkin's lymphoma

Metabolic or molecular imaging with fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) has emerged as a powerful imaging modality for diagnosis, staging, and therapy monitoring of a variety of cancers. The accuracy of FDG-PET as an imaging tool for the primary staging of lymphoma suffers from the absence of a reference criterion to which all imaging modalities can be compared. For ethical reasons, pathological diagnosis is usually not possible for all of the lesions and abnormalities found. In this article, the current state of the art for staging of primary lymphoma is reviewed and the implications for staging and the impact on patient management discussed. Whole-body PET using FDG is superior to conventional staging, i.e., physical examination, laboratory tests, plain radiography, and CT, by 10-20%. The sensitivity of FDG-PET varies for different regions of the body and appears lowest for infradiaphragmatic disease involvement. Staging with metabolic imaging leads in 10-40% of patients to a change in clinical stage. Highly variable results have been reported on whether up- or downstaging of lymphoma with PET leads to changes in the therapeutic approach for primary lymphoma.

Differential FDG accumulation associated with GLUT-1 expression in a patient with lymphoma

We herein report a case of malignant lymphoma that showed differential FDG accumulation associated with the degree of glucose transporter 1 (GLUT-1) expression. For clinical staging purpose, FDG-PET was performed on a 47-year-old male who had been diagnosed to have malignant lymphoma, diffuse medium B-cell type. Although an X-ray CT showed multiple and bulky lymphadenopathy including bilateral submandibular, deep cervical, supraclavicular, axillar, hilar, mesenteric and paraaortic regions, FDG-PET showed a high accumulation only in the bilateral submandibular and deep cervical region. An immunohistochemical analysis demonstrated a high GLUT-1 expression in the right cervical lymph node, which showed a high FDG uptake. On the other hand, a bone marrow specimen with diffuse lymphoma cell involvement indicated showed no FDG accumulation and also revealed a negative GLUT-1 expression. This case suggests that the differential FDG accumulation shown by lesions is associated with the degree of GLUT-1 expression in patients with lymphoma.

Limitations of PET for imaging lymphoma

The uptake of fluorine-18 fluorodeoxyglucose (FDG) is increased in processes with enhanced glycolysis, including malignancy. It is this property of FDG which is exploited in positron emission tomography (PET) imaging for lymphoma. FDG, whilst a good oncology tracer, is not perfect and there are limitations to its use. FDG may have low uptake in some types of lymphoma, predominantly low-grade lymphomas. High physiological uptake may occur within the bowel, urinary tract, muscle, salivary glands and lymphoid tissue. FDG is not specific for malignancy and increased uptake occurs in benign conditions with increased glycolysis such as infection, inflammation and granulomatous disease. Benign conditions usually have lower uptake than malignancy but there is overlap. These limitations of FDG mean that tumour may be 'missed', 'masked' or 'mimicked' by other pathology. These limitations are described in this article and methods to circumvent them where possible are discussed. These include performing baseline scans at presentation with lymphoma for comparison with post-treatment scans, simple manoeuvres to reduce physiological uptake such as administration of frusemide and diazepam and remaining alert to the possibility of alternative pathology in immunosuppressed patients. Patients with disease secondary to human immunodeficiency virus are a particular challenge in this regard as they often have dual or multiple pathology. One of the most important skills in PET reporting may be to recognise its limitations and be clear when a definitive answer cannot be given to the referring clinician's question. This may require using PET to direct the clinician to biopsy the site most likely to yield the correct diagnosis.

Utility of FDG-PET scanning in lymphoma by WHO classification

We retrospectively evaluated (18)fluoro-2-deoxyglucose positron emission tomography (FDG-PET) scans in 172 patients with lymphoma and correlated results with pathologic diagnosis using the World Health Organization (WHO) classification system. In total, FDG-PET detected disease in at least one site in 161 patients (94%) and failed to detect disease in 11 patients (6%). The most frequent lymphoma diagnoses were diffuse large B-cell lymphoma (LBCL; n = 51), Hodgkin lymphoma (HL; n = 47), follicular lymphoma (FL; n = 42), marginal zone lymphoma (MZL; n = 12), mantle cell lymphoma (MCL; n = 7), and peripheral T-cell lymphoma (PTCL; n = 5). FDG-PET detected disease in 100% of patients with LBCL and MCL and in 98% of patients with HL and FL. In contrast, FDG-PET detected disease in only 67% of MZL and 40% of PTCL. Comparison with bone marrow biopsies showed that FDG-PET was not reliable for detection of bone marrow involvement in any lymphoma subtype.

Early detection of relapse by whole-body positron emission tomography in the follow-up of patients with Hodgkin's disease

BACKGROUND

Relapse after treatment of Hodgkin's disease (HD) is usually identified as a result of the investigation of symptoms. We undertook this study to examine the value of whole-body positron emission tomography (PET) for the detection of preclinical relapse.

PATIENTS AND METHODS

Thirty-six patients underwent 2-[fluorine-18]fluoro-2-deoxy-D-glucose ((18)F-FDG) PET at the end of treatment and than every 4-6 months for 2-3 years after the end of polychemotherapy and/or radiotherapy. In those cases of abnormal (18)F-FDG accumulation a confirmatory study was performed 4-6 weeks later.

RESULTS

One patient had residual tumor and four patients relapsed during a follow-up of 5-24 months. All five events were correctly identified early by (18)F-FDG PET. Residual tumor or relapse was never first diagnosed based on clinical examination, laboratory findings or computed tomography (CT) studies. Two patients presented B symptoms and the three others were asymptomatic at the time of residual disease or relapse. Confirmation of residual disease or relapse was obtained by biopsy in four patients 1, 1, 5 and 9 months after PET and by unequivocal clinical symptoms and CT studies in one patient 3 months after PET. False-positive (18)F-FDG PET studies incorrectly suggested possible relapse in six other patients, but the confirmatory PET was always negative. Our study also provides important information about physiological (18)F-FDG uptake in the thymus.

CONCLUSIONS

Our data suggest the potential of (18)F-FDG PET to detect preclinical relapse in patients with HD. This could help identify patients requiring salvage chemotherapy at the time of minimal disease rather than at the time of clinically overt relapse. Further studies are warranted to determine the impact of PET on treatment management and outcome. In fact, the aim of follow-up procedures is not only to detect preclinical relapse but mainly to obtain better results by starting salvage treatment earlier. A cost-benefit analysis will also be necessary before (18)F-FDG PET can be used routinely in the follow-up of patients with HD.

Positron emission tomography in the management of lymphomas

Positron emission tomography is a functional imaging modality that capitalizes on biochemical changes within tumour cells to localize these changes within the body. As a functional imaging tool, unlike an anatomical imaging tool such as CT, it does not require enlargement of lymph nodes affected by disease but does require sufficient numbers of tumour cells to be present with altered biochemical function to visualize these disease sites. These changes are most commonly monitored using a glucose mimic fluorodeoxyglucose which is not only taken up into tumour cells but is trapped within these cells owing to alterations of the hexokinase and dephosphorylase enzymes. This review examines the current role of FDG PET imaging in patients with Hodgkins and Non-Hodgkins lymphoma and also speculates on future roles for this imaging modality.

Clinical impact of whole body FDG-PET on the staging and therapeutic decision making for malignant lymphoma

OBJECTIVES

The aim of this study is to evaluate the clinical impact of whole-body FDG-PET for the pre-therapeutic evaluation of malignant lymphoma and compared to that of 67Ga-scintigraphy when added to non-RI examinations.

METHODS

We examined 46 patients with malignant lymphoma including 42 newly diagnosed cases and 4 relapsed cases. Whole-body FDG-PET was started 63 minutes after the administration of FDG with ECAT EXACT HR+. The clinical stage of each patient was determined based on the results of a non-RI examination (consisting of physical examination, CT, gastrointestinal studies and bone marrow aspiration), 67Ga planar images and FDG-PET. Discrepant findings were verified based on the response to treatment and the findings of a follow-up examination more than 6 months after treatment. Finally, 152 nodal regions and 19 extranodal tissues were found to be involved by disease.

RESULTS

In the 152 nodal lesions, FDG-PET detected 54 nodal lesions in addition to 98 lesions detected by non-RI examinations, whereas 67Ga-scintigraphy detected 14 additional lesions. The sensitivity of non-RI, non-RI + 67Ga and non-RI + FDG was 64.5%, 73.7% and 100.0%, respectively. In 19 extranodal lesions, FDG-PET detected 5 extranodal lesions in addition to 13 lesions detected by non-RI examinations, whereas 67Ga-scintigraphy detected 1 additional lesion. The sensitivity of non-RI, non-RI + 67Ga and non-RI + FDG was 68.4%, 73.7% and 94.7%, respectively. When combining the FDG-PET findings with the non-RI findings, the improvement of the detectability was much higher than that when 67Ga findings were combined to the non-RI findings. For the staging of lymphoma, the non-RI and non-RI + 67Ga findings accurately diagnosed 76.1% and 80.4%, respectively, whereas the non-RI + FDG findings accurately diagnosed 82.6%. Finally, FDG-PET resulted in changes in the clinical management of 8 patients (17.4%).

CONCLUSIONS

FDG-PET offers more information in addition to the findings of conventional diagnostic methods than 67Ga-scintigraphy in order to accurately detect malignant lymphoma. FDG-PET can therefore play an important role in therapeutic decision making on lymphoma.

Positron emission tomography in non-Hodgkin's lymphoma (NHL): relationship between tracer uptake and pathological findings, including preliminary experience in the staging of low-grade NHL

Advances in imaging techniques have allowed more precise staging and better evaluation of the effect of new treatment modalities. The limitations of conventional morphologic imaging techniques are well known. Positron emission tomography (PET) using fluorine-18-labeled fluorodeoxyglucose is now routinely used for initial staging and re-evaluation during or after treatment of Hodgkin's disease and aggressive non-Hodgkin's lymphoma (NHL), but not in low-grade NHL. In the first part of this review, the relationship between glucose metabolism as measured by PET, pathological findings including histological grade and proliferative activity, and prognosis are analyzed. In the second part, the potential role of PET in the staging and follow-up of low-grade NHL is discussed. Published data indicate that PET may contribute to the management of low-grade follicular NHL.

Fusion PET-CT imaging of neurolymphomatosis

In a patient suffering from peripheral neuropathy due to neurolymphomatosis, fused PET-CT imaging, performed on a novel in-line PET-CT system, showed multiple small nodular lesions extending along the peripheral nerves corresponding to an early relapse of a transformed B-cell non-Hodgkin's lymphoma.