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

Primary gastric diffuse large B-cell lymphoma with orbital involvement: diagnostic usefulness of 18F-fluorodeoxyglucose positron emission tomography

A 38-year-old man presented to our hospital with abdominal pain and melena. Gastrointestinal endoscopy revealed a large gastric ulcer, and the pathological diagnosis of diffuse large B-cell lymphoma (DLBCL) was made based on immunohistochemical findings. Left diplopia developed soon after commencement of chemotherapy. Despite normal findings from head MRI, orbital involvement in DLBCL was detected with 18F-fluorodeoxyglucose positron emission tomography (FDG-PET). The patient was treated with salvage chemotherapy with success. Treatment analysis using FDG-PET for patients with DLBCL, especially for those with clinical symptoms and negative findings on conventional modalities, may be useful for assessing disease status and adjusting treatments.

FDG-PET/CT in lymphoma

Molecular Imaging has played a prominent role in the assessment of lymphoma for now almost three decades since the introduction of (67)Ga-citrate imaging for staging and restaging of both Hodgkin's and non-Hodgkin's lymphoma (HL and NHL). Since then other molecular probes have been investigated for more accurate pre- and posttreatment assessment of lymphomas but none of these probes was widely accepted and utilized until the emergence of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET). FDG-PET or FDG-PET/CT, which combines FDG-PET with CT scanning, is now widely utilized for response assessment of lymphoma after completion of therapy, for pretreatment staging, and, increasingly, also for assessment of response during therapy (therapy monitoring). Particularly for response assessment at therapy conclusion, FDG-PET has been shown to be considerably more accurate than CT or conventional MRI because of its ability to distinguish between viable tumor and necrosis or fibrosis in posttherapy residual mass (es) that are frequently present in patients with lymphoma without any other clinical or biochemical evidence of disease. FDG-PET/CT is therefore the noninvasive modality of choice for response classifications of HL and aggressive NHLs consistent with the recently revised, primarily FDG-PET/CT-based, response criteria for lymphoma. This review will highlight the most important applications of FDG-PET (FDG-PET/CT) in lymphoma emphasizing the strengths and pitfalls of this imaging approach, past and ongoing efforts to standardize the use of FDG-PET, particularly in response assessment and therapy monitoring. Other promising molecular probes for lymphoma imaging will also be briefly discussed.

18F-FDG PET, combined FDG-PET/CT and MRI for evaluation of bone marrow infiltration in staging of lymphoma: a systematic review and meta-analysis

BACKGROUND AND PURPOSE

Evaluation of bone marrow infiltration is an essential step in the staging of lymphoma. The accuracy of (18)F-fluorodeoxyglucose-positron emission tomography ((18)F-FDG PET), combined (18)F-fluorodeoxyglucose-positron emission tomography/computed tomography ((18)F-FDG-PET/CT) and magnetic resonance imaging (MRI) in diagnosing bone marrow involvement of lymphoma has never been systematically assessed, and the present systematic review was aimed at this issue.

METHODS

MEDLINE, EMBASE, Cochrane library and some other databases, from January 1995 to July 2010, were searched for initial studies. All the studies published in English or Chinese relating to the diagnostic value of (18)F-FDG PET, PET/CT and MRI for patients with bone marrow involvement of lymphoma were collected. We extracted data to calculate sensitivity, specificity, SROC curves and AUC and to test for heterogeneity. The statistic software called "Meta-Disc 1.4" was used for data analysis.

RESULT

In 32 included studies, PET/CT had the highest pooled sensitivity, 91.6% (95%CI: 85.1, 95.9) and highest pooled specificity, 90.3% (95%CI: 85.9, 93.7). PET/CT also had the highest pooled DOR, 68.89 (95%CI: 15.88, 298.92). The AUC of PET, PET/CT, and MRI were 0.9430, 0.9505 and 0.8764. There was heterogeneity among studies and no evidence of publication bias.

CONCLUSION

PET/CT was a highly sensitive and specific modality in diagnosing patients with bone marrow involvement in lymphoma. Compared with MRI and PET alone, PET/CT can play important roles in the staging of lymphoma.

Diagnostic and prognostic impact of 18F-FDG PET/CT in follicular lymphoma

PURPOSE

The aim of this study was to assess the usefulness of positron emission tomography/computed tomography in staging, prognosis evaluation and restaging of patients with follicular lymphoma.

METHODS

A retrospective study was performed on 45 patients with untreated biopsy-proven follicular lymphoma who underwent 18F-fluorodeoxyglucose PET/CT (FDG PET/CT) and CT before and after chemoimmunotherapy induction treatment (rituximab combined with cyclophosphamide, doxorubicin, vincristine and prednisone).

RESULTS

PET/CT detected more nodal (+51%) and extranodal (+89%) lesions than CT. PET/CT modified Ann Arbor staging in eight patients (18%). Five patients (11%) initially considered as being early stage (I/II) were eventually treated as advanced stage (III/IV). In this study, an initial PET/CT prognostic score was significantly more accurate than the Follicular Lymphoma International Prognostic Index score in identifying patients with poor prognosis (i.e. patients with incomplete therapeutic response or early relapse). The accuracy of PET/CT for therapeutic response assessment was higher than that of CT (0.97 vs 0.64), especially due to its ability to identify inactive residual masses. In addition, post-treatment PET/CT was able to predict patients' outcomes. The median progression-free survival was 48 months in the PET/CT-negative group as compared with 17.2 months for the group with residual uptake (p<10(-4)).

CONCLUSION

FDG PET/CT is useful for staging and assessing the prognosis and therapeutic response of patients with follicular lymphoma.

SUVmax in FDG-PET at the biopsy site correlates with the proliferation potential of tumor cells in non-Hodgkin lymphoma

The maximum standard uptake value (SUVmax) of the whole body on 18F-fluorodeoxyglucose positron emission tomography (FDG-PET) reflects the tumor aggressiveness in non-Hodgkin lymphoma (NHL). To clarify the correlation between SUVmax at the biopsy site and the proliferation potential of tumor cells, we studied 36 patients with untreated NHL and five with untreated Hodgkin lymphoma (HL) by measuring the Ki-67 proliferation index (MIB-1 labeling index) in biopsy specimens. The measured MIB-1 labeling index was categorized into seven levels: nearly 0%, 5-20%, 21-40%, 41-60%, 61-80%, 81-95%, and nearly 100%. Twenty-four lymph nodes (LNs) and 17 extranodal (EN) sites were biopsied. The reviewed diagnosis was eight indolent lymphomas, two mantle-cell lymphomas, 26 aggressive lymphomas, and five HLs. A positive correlation was observed between the SUVmax at the biopsy site and the MIB-1 labeling index in the 36 patients with NHL (r = 0.69, p < 0.001). The correlations were also observed in LN group (r = 0.60, p = 0.006) and EN group (r = 0.87, p < 0.001), respectively. In the five patients with HL, the MIB-1 labeling index was uniformly categorized in nearly 100%. The SUVmax correlates with the proliferation potential in the case of NHL.

FDG-PET in the assessment of patients with follicular lymphoma treated by ibritumomab tiuxetan Y 90: multicentric study

BACKGROUND

The aim of this study is the 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG)-positron emission tomography (PET) evaluation following radioimmunotherapy (RIT) with ibritumomab tiuxetan Y 90 in patients with non-Hodgkin's follicular lymphoma (FL).

MATERIALS AND METHODS

We retrospectively analyzed data from 59 relapsed or refractory FL patients treated with ibritumomab tiuxetan Y 90 in four different PET centers who had a PET scan carried out before and after RIT. Possible predictive factors of progression-free survival (PFS) were studied through univariate and multivariate analysis.

RESULTS

The post-RIT PET documented 45.8% complete responders (CR), 25.4% partial responders (PR) and 28.8% nonresponders [stable disease + progressive disease], with an overall survival of 71.2% (range 59.5%-90.9%). With a median follow-up period of 23 months, the univariate analysis documented a statistically significant relation between disease extent before RIT and response to treatment with respect to PFS (P = 0.015), while all the other prognostic factors showed no significant correlation. When carrying out the multivariate analysis, post-RIT PET resulted as the lonely independent predictor of PFS (P < 0.00001).

CONCLUSIONS

RIT is an effective therapy in FL patients, as confirmed in our study too. Disease extension before treatment and response to RIT, as assessed by FDG-PET, result as main predictors of PFS, with the post-RIT PET result being the only independent predictive factor.

(18)F-FDG avidity in lymphoma readdressed: a study of 766 patients

PET/CT with (18)F-FDG is an important noninvasive diagnostic tool for management of patients with lymphoma, and its use may surpass current guideline recommendations. The aim of the present study is to enlarge the growing body of evidence concerning (18)F-FDG avidity of lymphoma to provide a basis for future guidelines.

METHODS

The reports from (18)F-FDG PET/CT studies performed in a single center for staging of 1,093 patients with newly diagnosed Hodgkin disease and non-Hodgkin lymphoma between 2001 and 2008 were reviewed for the presence of (18)F-FDG avidity. Of these patients, 766 patients with a histopathologic diagnosis verified according to the World Health Organization classification were included in the final analysis. (18)F-FDG avidity was defined as the presence of at least 1 focus of (18)F-FDG uptake reported as a disease site. Nonavidity was defined as disease proven by clinical examination, conventional imaging modalities, and histopathology with no (18)F-FDG uptake in any of the involved sites.

RESULTS

At least one (18)F-FDG-avid lymphoma site was reported for 718 patient studies (94%). Forty-eight patients (6%) had lymphoma not avid for (18)F-FDG. (18)F-FDG avidity was found in all patients (100%) with Hodgkin disease (n = 233), Burkitt lymphoma (n = 18), mantle cell lymphoma (n = 14), nodal marginal zone lymphoma (n = 8), and lymphoblastic lymphoma (n = 6). An (18)F-FDG avidity of 97% was found in patients with diffuse large B-cell lymphoma (216/222), 95% for follicular lymphoma (133/140), 85% for T-cell lymphoma (34/40), 83% for small lymphocytic lymphoma (24/29), and 55% for extranodal marginal zone lymphoma (29/53).

CONCLUSION

The present study indicated that with the exception of extranodal marginal zone lymphoma and small lymphocytic lymphoma, most lymphoma subtypes have high (18)F-FDG avidity. The cumulating evidence consistently showing high (18)F-FDG avidity in the potentially curable Burkitt, natural killer/T-cell, and anaplastic large T-cell lymphoma subtypes justifies further investigations of the utility of (18)F-FDG PET in these diseases at presentation.

PET and PET/CT for response evaluation in lymphoma: Current practice and developments

Positron emission tomography (PET) using the radiolabelled glucose analog 2-[18F]fluoro-2-deoxy-d-glucose (FDG) is increasingly used for response assessment in patients with Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). These patients often present with a residual mass after therapy, but only a minority will relapse as most of these masses consist of inactive fibrosis. However, some patients have residual disease after first-line treatment and they can benefit from additional or early salvage therapy. Special interest for early, but accurate, assessment of response is growing accordingly. Conventional radiological techniques cannot differentiate between active tumoural tissue and fibrosis in these masses. In contrast, FDG-PET has the ability to differentiate between viable tumour and fibrosis and has been evaluated as an initial staging tool, for response assessment after completion of therapy and as a prognostic marker early during treatment. In this review, we will focus especially on the value of PET for response assessment.

Aggressive and indolent non-Hodgkin's lymphoma: Response assessment by Integrated International Workshop Criteria

Until recently, response assessment in patients with lymphoma was primarily performed by computed tomography (CT). Based on CT, International Workshop Criteria (IWC) were developed and widely used. Fluorodeoxyglucose Positron Emission Tomography (FDG-PET) is a more sensitive and specific imaging technique for the detection of residual disease in lymphoma, and Revised Integrated International Workshop Criteria (IWC + PET) were recently proposed by the members of the International Harmonization Project (IHP), which combine both imaging techniques. We determined whether these new IWC + PET-criteria, can more accurately predict outcome compared to IWC-criteria in aggressive and indolent non-Hodgkin's lymphoma (NHL), and therefore correlated IWC and IWC + PET response with time-to-next-treatment (TNT) in 69 patients with NHL. We demonstrated that IWC + PET-guidelines are highly recommended over IWC-guidelines for patients with potentially-curable and routinely FDG-avid lymphoma. In contrast, no additional value of IWC + PET was demonstrated in a small group of patients with incurable histological subtypes.

Predictive value and diagnostic accuracy of F-18-fluoro-deoxy-glucose positron emission tomography treated grade 1 and 2 follicular lymphoma

F-18-fluoro-deoxy-glucose positron emission tomography (PET) is a powerful tool for the imaging of aggressive B-cell lymphomas. In contrast, there is relatively little data on PET in follicular lymphoma grade 1 (FL-1) and grade 2 (FL-2). In this manuscript, we present our findings utilizing PET in treated FL-1 and FL-2. A retrospective review of patients who underwent PET examinations at our institution produced 95 PET examinations among 31 patients with FL-1 and FL-2. PET was obtained at initial staging, mid-induction and post-treatment. Results were compared with clinical follow-up. PET had high sensitivity (95%) and specificity (88%) for lesion detection in treated FL-1 and FL-2. Abnormal foci in FL-1 and FL-2 had similar intensities. Post-induction PET positive patients had shorter mean progression free survivals compared with PET negative patients (p-value < or =0.001), post-salvage PET positive trended toward shorter mean response duration compared with negative patients (p-value: 0.09). Our results indicate that PET is accurate in the diagnostic assessment of treated FL-1 and FL-2 and, post-treatment PET positive patients are likely to relapse prior to PET negative patients.

PET imaging in lymphoma

PET has become a cornerstone procedure in modern lymphoma management. This paper reviews, from a clinical point of view, the evidence for using PET in the different subtypes of lymphoma and the different steps of their management. The reader is given an overview of the current PET-based interventional lymphoma trials and an insight into possible future developments in the field, including new PET tracers.

High SUV uptake on FDG-PET/CT predicts for an aggressive B-cell lymphoma in a prospective study of primary FDG-PET/CT staging in lymphoma

BACKGROUND

Data assessing the role of positron emission tomography (PET)/computed tomography (CT) imaging in lymphoma staging is still being accumulated and current staging is based primarily on CT. This study aims to compare the value of PET/CT over conventional CT and bone marrow biopsy (BMB) in the initial evaluation of patients with lymphoma.

METHODS

Data on 122 patients with PET/CT scans as part of their initial staging were prospectively collected and reviewed. All patients had complete staging, including BMB.

RESULTS

Among the 122 patients, 101 had non-Hodgkin's lymphoma (NHL) and 21 had Hodgkin's lymphoma (HL). Compared with conventional CT, PET/CT upstaged 21 (17%) cases [B-cell non-Hodgkin's lymphoma (B-NHL), 12; T-cell non-Hodgkin's lymphoma (T-NHL), 3; HL, 6]. Of significance, in 13 patients with 2-[fluorine-18]fluoro-2-deoxy-D-glucose (FDG)-avid splenic lesions, four had normal CT findings. A maximum FDG uptake of >10 standardized uptake value (SUV) seems to significantly correlate with an aggressive B-cell lineage (odds ratio 2.47, 95% confidence interval 2.23-2.70). Overall, PET scan was concordant with BMB results in 108 (89%) and discordant in 14 (11%) cases. In HL, our data show that PET scan and marrow results agreed in 19 of the cases (90%), being concordantly negative in 18 cases and concordantly positive in one, giving a negative predictive value (NPV) of 100%, sensitivity of 100% and specificity of 90%. Of note, all 13 with early-stage HL had negative PET/CT scan and BMB. In NHL, all 17 cases of T-NHL had concordant PET and BMB results. In patients with aggressive B-NHL, BMB and PET/CT agreed in 58 patients (92%) and disagreed in five (8%), while the corresponding rates in indolent B-cell lymphoma were 14 (67%) and seven patients (33%), respectively. All seven were falsely negative.

CONCLUSIONS

PET/CT upstages 17% of cases and detects occult splenic involvement. This may have potential therapeutic and prognostic implications. SUV >10 may predict for an aggressive histology. Except for indolent B-NHL, our data show that PET scans have a good overall NPV in excluding lymphomatous bone marrow involvement. This is particularly true of early-stage HL, suggesting that BMB may be safely omitted in this group.

Comparison of CT, PET, and PET/CT for staging of patients with indolent non-Hodgkin's lymphoma

PURPOSE

The aim was to investigate the potential impact of positron emission tomography (PET)/computed tomography (CT) as compared to PET and CT on the staging of patients with indolent lymphoma.

PROCEDURES

PET/CTs from 45 patients with indolent lymphoma undergoing staging or restaging were studied. Clinical follow-up, additional imaging, and histology served as the gold standard.

RESULTS

PET/CT correctly diagnosed 92 nodal regions as positive for lymphomatous involvement and 458 as disease free vs 68 and 449 for PET and 64 and 459 for CT, respectively. The respective sensitivities, specificities, and accuracies were 99%, 100%, and 99.8% for PET/CT, 68%, 97.5%, and 92.2% for PET, and 70%, 100%, and 94.7% for CT. PET/CT performed significantly better than PET (p < 0.001 for sensitivity, specificity, and accuracy) and CT (p < 0.001 for sensitivity and accuracy). PET/CT also correctly identified significantly more extra-nodal lesions (22) than CT (14) and PET (nine).

CONCLUSIONS

PET/CT provides significantly more accurate information compared to PET and CT for the staging and re-staging of patients with indolent lymphoma.

Value of [18F]fluorodeoxyglucose positron emission tomography in the management of follicular lymphoma: the end of a dilemma?

BACKGROUND

[18F]Fluorodeoxyglucose (FDG) positron emission tomography (PET) is a powerful tool for the imaging of various lymphomas. Despite its high FDG avidity, there is little data on PET in follicular lymphoma (FL). In this work, we present findings concerning PET at staging and posttreatment evaluation in FL.

PATIENTS AND METHODS

A total of 181 PET scans were evaluated in 117 patients with FL in a retrospective study. Positron emission tomography-based results were compared with conventional staging in 82 patients. Posttreatment PET evaluation was performed in 99 patients; there were comparable progression-free survivals of PET-positive and PET-negative patients.

RESULTS

Positron emission tomography showed more involvement than computed tomography (CT) with clinical examination in 41 of 82 patients (50%), less in 11 of 82 (13%); the same extension was found in 27 of 82 patients (33%), and 3 patients revealed discordant foci visible on PET only and lymphadenopathy without PET activity (P < .001). Including the results of trephine biopsy, PET finally upstaged FL in 15 of 82 patients (18%), which was projected in change of treatment strategy. There were 73 of 99 negative posttreatment PET scans; 54 of 73 PET-negative patients (74%) remain in complete remission (median follow-up, 27 months); 19 (26%) of them relapsed with median of 12 months. Fourteen of 20 (70%) PET-positive patients relapsed with a median of 4.5 months regardless of findings on CT and subsequent therapy. The difference in relapse rates between PET-positive and PET-negative patients is statistically significant (P < .001).

CONCLUSION

Positron emission tomography at staging is able to substantially change treatment strategy in an important proportion of patients with FL. Persisting PET positivity after treatment predicts for a high risk of an early relapse and can identify patients with poor prognosis.

18F-FDG-PET in patients with malignant lymphoma having long-term follow-up: staging and restaging, and evaluation of treatment response and recurrence

OBJECTIVE

The aim of this study was to evaluate the diagnostic accuracy of positron emission tomography (PET) with 2-[18F]fluoro-2-deoxy-D-glucose (18F-FDG) for staging/restaging, evaluating the treatment response, and screening of recurrence in patients with malignant lymphoma (ML) during long-term follow-up, and to compare that with computer tomography (CT)/magnetic resonance imaging (MRI).

METHODS

The study was conducted in 59 ML patients who underwent whole-body 18F-FDG-PET examinations three times or more from October 1998 to August 2006. The location of the lesions in the patients with positive findings on 18F-FDG-PET and/or the corresponding CT/MRI was classified into supradiaphragmatic (n = 10), infradiaphragmatic (n = 7), and extranodal sites (n = 20), and the findings were compared on a site basis according to the gold standard, which consisted of all clinical information available, including follow-up results.

RESULTS

A total of 156 18F-FDG-PET examinations for which the corresponding CT/MRI images were also available were evaluated, and a total of 305 sites showed positive findings on 18F-FDG-PET and/or CT/MRI. Concordant positive findings were obtained in 76% for staging/restaging, 34% for evaluation of the treatment response, and 50% for screening of recurrence. The accuracy of 18F-FDG-PET versus CT/MRI was 92% versus 84% (P = 0.06) for staging/restaging, 84% versus 50% (P < 0.05) for the evaluation of the treatment response, and 83% versus 72% (P = 0.21) for the screening of recurrence. At pathologic sites with discrepant findings between 18F-FDG-PET and CT/MRI (n = 122), the frequency of accurate diagnosis by 18F-FDG-PET (76%) was higher than that by CT/MRI (24%), especially for the evaluation of the treatment response.

CONCLUSIONS

18F-FDG-PET is expected to play a significant role in the management of ML patients even after effective treatment is initiated.

Positron emission tomography changes management, improves prognostic stratification and is superior to gallium scintigraphy in patients with low-grade lymphoma: results of a multicentre prospective study

PURPOSE

Positron emission tomography (PET) was evaluated in low-grade non-Hodgkin lymphoma (NHL) to determine its impact on staging and management and to compare PET and gallium scans.

METHODS

PET resulted in management plan changes in 74 patients with untreated low-grade NHL stages I to III. Patient outcomes to 12 months were documented.

RESULTS

PET identified additional lesions in 50% of patients, led to a change in stage in 32%, and had a significant impact on management in 34%. Inferior progression-free survival was noted in patients with additional lesions detected by PET (p=0.001) and in the 28% of patients upstaged by PET to stage III or IV (p=0.024). In a subset of 16 patients undergoing both PET and gallium scans, PET was found to be superior.

CONCLUSION

PET has a major role in the management of low-grade NHL in addition to its proven role in aggressive lymphoma.

FDG-PET scans in patients with lymphoma

Lymphoma comprises a complex set of diseases, including Hodgkin and non-Hodgkin subtypes. An expected goal of management is chronic disease control over decades in most patients with indolent subtypes, and cure is a realistic target for aggressive histologies, including Hodgkin lymphoma. Making methods available to better assess prognosis and to more specifically tailor therapy toward individual subtypes is a priority. Positron emission tomography using the tracer (18)fluoro-2-deoxyglucose (FDG-PET) has become a valuable tool in the care of patients with lymphoma; it contributes information on staging and response assessment that has the potential to affect and improve patient care. This imaging modality is also being explored as an early response assessor, potentially allowing early prediction of an individual's response to a specific therapy. This information ultimately may lead to modifications of treatment to improve efficacy or reduce toxicity. Although FDG-PET offers valuable information, it is important to recognize its limitations as well as areas that require further exploration in order to optimally integrate its use into the clinical management of lymphoma patients.

The impact of fluorodeoxyglucose-positron emission tomography in primary staging and patient management in lymphoma patients

Fully diagnostic positron emission tomography (PET)/CT scans acquired during oral and intravenous contrast can be provided to patients and referring physicians in a single imaging session. Although FDG uptake varies, most low-grade lymphomas exhibit sufficient FDG avidity to also be staged reliably with FDG PET/CT. PET/CT imaging is more accurate for lymphoma staging than PET or CT alone and has substantial impact on patient management. This accurate whole-body glucose metabolic survey should serve as the baseline for subsequent treatment response evaluations. PET/CT has evolved to become the modality of choice for staging of nodal and extranodal lymphoma, for assessing therapeutic response, and for establishing patient prognosis.

Therapeutic evaluation and prognostic value of interim hybrid PET/CT with (18)F-FDG after three to four cycles of chemotherapy in non-Hodgkin's lymphoma

PURPOSE

Modern risk-adapted treatment requires accurate assessment of the patient's prognosis. This study assessed the value of hybrid PET/CT with 2-[18F]fluoro-2-deoxy-d-glucose ((18)F-FDG) after 3-4 cycles of chemotherapy for early evaluation of response to therapy and prediction of progression-free survival (PFS) in non-Hodgkin's lymphoma (NHL).

METHODS

Sixty-one consecutive NHL patients (37 male and 24 female) were included. The (18)F-FDG hybrid PET/CT scans were performed prior to chemotherapy (initial scan) and after 3-4 cycles of chemotherapy (interim scan). Interim FDG findings were correlated to the PFS using Kaplan-Meier analysis. Regression analyses were employed to test for independence of established pretreatment prognostic factors.

RESULTS

After 3-4 cycles of chemotherapy, positive (18)F-FDG lesions were found in 28 patients, minimal residual uptake (MRU) in 8 and negative scans in 25 patients. In FDG-positive group, 22 patients showed progress and three died. Nine (18)F-FDG-negative patients and 4 patients from the MRU group relapsed. Survival analyses showed highly significant associations between early interim FDG imaging and PFS (P < 0.0005). The 2-year PFS rate for FDG-negative patients was 72.2 and 23.0% for FDG-positive patients. The regression model showed that the predictive value of FDG imaging owed its significance to the very high hazard ratio between patients with positive FDG imaging and patients with negative FDG imaging (P < 0.001).

CONCLUSIONS

Early interim FDG imaging is an excellent and independent predictor of PFS in NHL. An early assessment of chemotherapy response with FDG scans may provide useful information for selection of patients for alternative therapeutic strategies.

Fluorine-18 fluorodeoxyglucose positron emission tomography in mature T-cell and natural killer cell malignancies

Fluorine-18 fluorodeoxyglucose (FDG)-positron emission tomography (PET) is useful in Hodgkin and B-cell lymphomas. Few data exist on T-cell and natural killer (NK)-cell lymphomas. Thirty consecutive T-cell and NK-cell lymphomas were investigated with PET-computerized tomography (CT). In 12 NK-cell lymphomas, all nasal/extranasal lesions were FDG-avid. In nasal/maxillary areas, FDG-avid tumours were consistently more localised than on CT, suggesting that soft tissue masses on CT were partly due to inflammation. These findings have important implications in radiotherapy planning. In two NK-cell lymphomas, PET did not detect morphologically occult marrow infiltration uncovered by in situ hybridisation for Epstein-Barr-virus-encoded small RNA. In angioimmunoblastic lymphoma (n = 7), peripheral T-cell lymphoma, unspecified (PTCL-U, n = 4) and anaplastic large cell lymphoma (ALCL, n = 3), involved nodal/extranodal sites shown on CT and/or biopsy were concordantly PET-positive. In one PTCL-U, PET detected FDG-avid marrow infiltrations not shown on biopsies. In contrast, cutaneous ALCL (n = 1) and mycosis fungoides (n = 2) showed minimal FDG uptake. In one case of T-cell large granular lymphocyte leukaemia, marrow, nodal and bowel infiltrations were not FDG-avid. PET maximum standardised uptake value did not correlate with clinicopathological features and prognosis. These observations defined the pre-treatment value of PET-CT in T-cell and NK-cell lymphomas. The post-treatment role requires further studies.

Predictive and prognostic value of FDG-PET

The predictive and prognostic value of fluorodeoxyglucose (FDG)-positron emission tomography (PET) in non-small-cell lung carcinoma, colorectal carcinoma and lymphoma is discussed. The degree of FDG uptake is of prognostic value at initial presentation, after induction treatment prior to resection and in the case of relapse of non-small cell lung cancer (NSCLC). In locally advanced and advanced stages of NSCLC, FDG-PET has been shown to be predictive for clinical outcome at an early stage of treatment. In colorectal carcinoma, limited studies are available on the prognostic value of FDG-PET, however, the technique appears to have great potential in monitoring the success of local ablative therapies soon after intervention and in the prediction and evaluation of response to radiotherapy, systemic therapy, and combinations thereof. The prognostic value of end-of treatment FDG-PET for FDG-avid lymphomas has been established, and the next step is to define how to use this information to optimize patient outcome. In Hodgkin's lymphoma, FDG-PET has a high negative predictive value, however, histological confirmation of positive findings should be sought where possible. For non-Hodgkin's lymphoma, the opposite applies. The newly published standardized guidelines for interpretation formulates specific criteria for visual interpretation and for defining PET positivity in the liver, spleen, lung, bone marrow and small residual lesions. The introduction of these guidelines should reduce variability among studies. Interim PET offers a reliable method for early prediction of long-term remission, however it should only be performed in prospective randomized controlled trials. Many of the diagnostic and management questions considered in this review are relevant to other tumour types. Further research in this field is of great importance, since it may lead to a change in the therapeutic concept of cancer. The preliminary findings call for systematic inclusion of FDG-PET in therapeutic trials to adequately position FDG-PET in treatment time lines.

Impact of [18f] fluorodeoxyglucose positron emission tomography on staging and management of early-stage follicular non-hodgkin lymphoma

PURPOSE

Accurate staging is critical to select patients with early-stage (I-II) follicular lymphoma (ESFL) suitable for involved-field radiotherapy (IFRT) and to define the radiotherapy portal. We evaluated the impact of fluorodeoxyglucose (FDG) PET on staging, treatment, and outcome for patients with ESFL on conventional staging.

METHODS AND MATERIALS

Forty-two patients with untreated ESFL (World Health Organization Grade I-IIIa, or "low grade") following a minimum of physical examination, computerized tomography, and bone marrow examination (conventional assessment) and who had staging PET from June 1997 to June 2006 were studied retrospectively. Stage allocation was based on routine imaging reports. Disease sites, stage, and management plan were recorded based on conventional assessment or conventional assessment plus PET.

RESULTS

FDG avidity was demonstrated in 97% of patients in whom disease was evident on conventional assessment after biopsy. PET findings suggested a change of stage or management in 19 patients: 13 (31%) who were upstaged to Stage III-IV, altering ideal management from IFRT to systemic therapy, and 6 (14%) who had the involved field enlarged, including 4 upstaged from Stage I to II. Of these 19 cases, PET findings were considered true positive in 8 patients, indeterminate in 10, and false positive in only 1 patient.

CONCLUSIONS

Our data confirm that ESFL is usually FDG-avid. In routine practice, PET has the potential to upstage and thereby alter management in a high proportion of patients with apparent ESFL.

Response assessment in lymphoma

The lymphomas are a heterogeneous group of malignant diseases. They are divided into two broad groups: Hodgkin's disease (HD) and non-Hodgkin's lymphoma (NHL). Patients suffering from HD and NHL can be cured by appropriate chemotherapy and/or radiotherapy. Accurate staging and response assessment is essential to guide management decisions. The International Workshop Group (IWG) criteria, published in 1999, have become the widely accepted standard for response assessment in NHL. Although the IWG criteria have proved extremely useful in the standardization of treatment response, they do have a number of limitations. As a consequence of this, together with advances in functional imaging, revised criteria have been published recently. The aim of this review is to describe the evidence supporting the available imaging techniques, the limitations of each technique, and how these should be applied in clinical practice. We briefly review the corresponding response criteria for central nervous system (CNS) lymphomas, and take a look at novel imaging techniques that may play a role in the future.

The usefulness of (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) and a comparison of (18)F-FDG-pet with (67)gallium scintigraphy in the evaluation of lymphoma: relation to histologic subtypes based on the World Health Organization classification

BACKGROUND

Although studies comparing conventional imaging modalities with (18)F-fluorodeoxyglucose positron emission tomography ((18)F-FDG-PET) for the detection of lymphoma and although the relations between (18)F-FDG-PET and histologic types were reported previously, most studies were not systematic and involved relatively small numbers of patients.

METHODS

Two hundred fifty-five patients with lymphoma had their disease staged using (18)F-FDG-PET, and 191 of those patients also were assessed using gallium-67 scintigraphy ((67)Ga). Disease sites were identified on a site-by-site basis using computed tomography scans and/or magnetic resonance imaging. The results of these conventional imaging modalities were compared with the results from (8)F-FDG-PET and (67)Ga, and correlations between the imaging results and pathologic diagnoses were evaluated by using the World Health Organization classification system.

RESULTS

Of 913 disease sites in 255 patients, (18)F-FDG-PET identified >97% of disease sites of Hodgkin lymphoma (HL) and aggressive and highly aggressive non-Hodgkin lymphoma. For indolent lymphoma, the detection rate of (18)F-FDG-PET was 91% for follicular lymphoma (FL); 82% for extranodal marginal zone B-cell lymphoma of mucosa-associated lymphoid tissue, irrespective of plasmacytic differentiation; and approximately 50% for small lymphocytic lymphoma (SLL) and splenic marginal zone lymphoma (SMZL). The results from (67)Ga were similar to those from (18)F-FDG-PET for most histologic subtypes. However, the sensitivity of (67)Ga was unexpectedly poor for FL, for mantle cell lymphoma (MCL), and for the nasal type of natural killer/T-cell lymphoma (NK/T-nasal), ranging from 30% to 38%.

CONCLUSIONS

(18)F-FDG-PET was useful for all histologic subtypes of lymphoma other than SLL and SMZL. Compared with (67)Ga, the authors strongly recommend the use of (18)F-FDG-PET in patients with FL, MCL, and NK-nasal.

The International Harmonization Project for response criteria in lymphoma clinical trials

Clinical trials are critical to the development of newer and more effective treatments. Standardized response criteria are essential to assess and compare the activity of various therapies within and among studies and to facilitate the evaluation of new treatments by regulatory agencies. The International Harmonization Project developed revised guidelines with the goal of improved comparability among studies, leading to accelerated new agent development resulting in the rapid availability of improved therapies for patients who have lymphoma. Modifications of these recommendations are expected as new information and improved technologies become available.

Imaging in staging of malignant lymphoma: a systematic review

Computed tomography (CT) is currently the most commonly used means for staging malignant lymphoma. 18F-fluoro-2-deoxyglucose positron emission tomography (FDG-PET), FDG-PET/CT fusion, and whole-body magnetic resonance imaging (WB-MRI) are potential alternatives. The purpose of this study was to systematically review published data on the diagnostic performance of CT, FDG-PET, FDG-PET/CT fusion, and WB-MRI in staging of malignant lymphoma. In addition, technical aspects, procedures, advantages, and drawbacks of each imaging modality are outlined. Three CT studies, 17 FDG-PET studies, and 4 FDG-PET/CT fusion studies were included in this systematic review. The studies were of moderate methodological quality and used different scoring systems to stage malignant lymphoma. CT remains the standard imaging modality for initial staging of malignant lymphoma, while FDG-PET has an essential role in restaging after treatment. Early results suggest that FDG-PET/CT fusion outperforms both CT alone and FDG-PET alone. Data on the diagnostic performance of WB-MRI are lacking. Future well-designed studies, expressing their results according to the Ann Arbor staging system, are needed to determine which imaging modality is most accurate and cost-effective in staging malignant lymphoma.

2-[18F]fluoro-2-deoxyglucose positron-emission tomography in staging, response evaluation, and treatment planning of lymphomas

2-[18F]fluoro-2-deoxyglucose positron-emission tomography (FDG-PET) is used increasingly in the clinical management of lymphomas. With regard to staging, FDG-PET is more sensitive and specific than conventional staging methods in FDG avid lymphomas (ie, Hodgkin lymphoma and most aggressive non-Hodgkin lymphomas). Despite methodological problems, in particular the lack of a valid reference test, FDG-PET is approved and generally used for this purpose. With regard to response evaluation, FDG-PET at the end of treatment seems to aid considerably in differentiating between residual masses with or without residual lymphoma. Hence, new revised response criteria have been proposed, incorporating the result of FDG-PET at the end of treatment. An early interim FDG-PET scan after 1 to 3 cycles of chemotherapy is a very strong predictor of outcome, and trials are now in progress testing treatment modifications on this basis. With regard to treatment planning, in the context of combined-modality therapy, radiotherapy for lymphomas is moving toward more conformal techniques reducing the irradiated volume to include only the macroscopic lymphoma. In this situation, accurate imaging is essential, and FDG-PET coregistered with the planning computed tomography (CT) scan is used increasingly. The availability of PET/CT scanners suited for virtual simulation has aided this process. However, clinical data evaluating this technique are at present sparse.

The role of FDG-PET scans in patients with lymphoma

18-Fluoro-deoxyglucose positron emission tomography (FDG-PET) is a noninvasive, 3-dimensional imaging modality that has become widely used in the management of patients with malignant lymphomas. This technology has been demonstrated to be more sensitive and specific than either (67)gallium scintigraphy or computerized tomography, providing a more accurate distinction between scar or fibrosis and active tumor. PET scans have been evaluated in pretreatment staging, restaging, monitoring during therapy, posttherapy surveillance, assessment of transformation, and, more recently, as a surrogate marker in new drug development. Data to support these various roles require prospective validation. Moreover, caution must be exercised in the interpretation of PET scans because of technical limitations, variability of FDG avidity among the different lymphoma histologic subtypes, and in the large number of etiologies of false-negative and false-positive results. Recent attempts to standardize PET in clinical trials and incorporation of this technology into uniformly adopted response criteria will hopefully lead to improved outcome for patients with lymphoma.

Value of positron emission tomography in staging ocular adnexal lymphomas and evaluating their response to therapy

BACKGROUND AND OBJECTIVE

An observational case series to assess the value of positron emission tomography (PET) in staging ocular adnexal lymphomas and evaluating their response to therapy.

PATIENTS AND METHODS

The clinical records of 16 consecutive patients with ocular adnexal lymphoma for whom pretreatment and posttreatment PET scans and corresponding computed tomography (CT) and magnetic resonance imaging (MRI) scans were available were compared.

RESULTS

Pretreatment PET scans demonstrated fluorine 18-fluorodeoxyglucose (FDG) positive lesions in 15 orbits of 12 patients. In 1 patient with low-grade follicular lymphoma of the orbit, PET revealed an additional focus of lymphoma in the deltoid muscle that was missed on clinical examination and conventional radiography. All of the posttreatment PET scans showed complete resolution of FDG uptake, suggesting good response to therapy. However, posttreatment CT and MRI scans demonstrated residual masses in 3 patients.

CONCLUSIONS

PET is valuable for initial staging of ocular adnexal lymphomas and may be a good adjunct to conventional imaging in evaluation of response to therapy.

Normal and Abnormal Patterns of 18F-Fluorodeoxyglucose PET/CT in Lymphoma

In spite of the high performance of 18F-fluorodeoxyglucose (FDG) PET for the evaluation of lymphoma, inherent limitations of this modality underscore the additional value of PET/CT as an important tool in the assessment of this disease. Accumulating data on the use of PET/CT in lymphoma indicate the contribution of hybrid imaging to improved interpretation accuracy of PET using FDG and CT. Knowledge of the normal and abnormal patterns of FDG-PET/CT imaging and their variability in patients with lymphoma is important to provide a comprehensive clinically significant interpretation that has an impact on patient management and potentially on outcome.

The role of FDG PET in the management of lymphoma: what is the evidence base?

[18F]Fluorodeoxyglucose positron emission tomography (18F-FDG PET) is playing an increasing role in the management of both Hodgkin and non-Hodgkin lymphoma, offering potential advantages in the accuracy of disease assessment at a number of points in the management pathway. This review evaluates the current level of confidence in the use of PET technology in (1) initial staging, (2) the assessment of early response to chemotherapy, (3) the assessment of residual masses at completion of initial treatment, (4) follow-up, and (5) radiotherapy planning.

PET/CT: form and function

Functional imaging with positron emission tomography (PET) is playing an increasingly important role in the diagnosis and staging of malignant disease, image-guided therapy planning, and treatment monitoring. PET with the labeled glucose analogue fluorine 18 fluorodeoxyglucose (FDG) is a relatively recent addition to the medical technology for imaging of cancer, and FDG PET complements the more conventional anatomic imaging modalities of computed tomography (CT) and magnetic resonance imaging. CT is complementary in the sense that it provides accurate localization of organs and lesions, while PET maps both normal and abnormal tissue function. When combined, the two modalities can help both identify and localize functional abnormalities. Attempts to align CT and PET data sets with fusion software are generally successful in the brain; other areas of the body is more challenging, owing to the increased number of degrees of freedom between the two data sets. These challenges have recently been addressed by the introduction of the combined PET/CT scanner, a hardware-oriented approach to image fusion. With such a device, accurately registered anatomic and functional images can be acquired for each patient in a single scanning session. Currently, over 800 combined PET/CT scanners are installed in medical institutions worldwide, many of them for the diagnosis and staging of malignant disease and increasingly for monitoring of the response to therapy. This review will describe some of the most recent technologic developments in PET/CT instrumentation and the clinical indications for which combined PET/CT has been shown to be more useful than PET and CT performed separately.

Revised Response Criteria for Malignant Lymphoma

Purpose

Standardized response criteria are needed to interpret and compare clinical trials and for approval of new therapeutic agents by regulatory agencies.

Methods

The International Working Group response criteria (Cheson et al, J Clin Oncol 17:1244, 1999) were widely adopted, but required reassessment because of identified limitations and the increased use of [18F]fluorodeoxyglucose-positron emission tomography (PET), immunohistochemistry (IHC), and flow cytometry. The International Harmonization Project was convened to provide updated recommendations.

Results

New guidelines are presented incorporating PET, IHC, and flow cytometry for definitions of response in non-Hodgkin's and Hodgkin's lymphoma. Standardized definitions of end points are provided.

Conclusion

We hope that these guidelines will be adopted widely by study groups, pharmaceutical and biotechnology companies, and regulatory agencies to facilitate the development of new and more effective therapies to improve the outcome of patients with lymphoma.

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.

Hodgkin's and Non-Hodgkin's Lymphomas

The diagnosis and management of lymphoma have undergone significant changes in the past 20 years. For example, new immunophenotypic and molecular methods have replaced traditional histology-based classification schemes for lymphoma. Fluorine-18-deoxyglucose (FDG) positron emission tomography (PET) has evolved into a potent staging tool and prognostic indicator in many kinds of lymphoma. The role of radiation therapy, especially in patients who have early-stage Hodgkin's disease, has changed substantially. The introduction of anti-CD 20 antibody therapy (Rituximab) has improved the treatment of B-cell lymphoma. These changes are linked with higher expectations for imaging, such as detection of more subtle lymphoma manifestations, evaluation of residual changes, and better assessment of early response. This article reviews clinical and radiologic features of both Hodgkin's disease and non-Hodgkin's lymphoma. It also describes the radiologic staging of lymphoma and the emerging role of FDG-PET for assessing lymphoma.

Predictive Role of Positron Emission Tomography in the Outcome of Patients with Follicular Lymphoma

PURPOSE

The purpose of this study was to evaluate the reliability of positron emission tomography (PET) in patients with follicular lymphoma (FL) after induction treatment.

PATIENTS AND METHODS

In all, 45 previously untreated patients with FL were studied with PET and computed tomography (CT) scans after chemotherapy induction treatment (fludarabine-containing regimens and CHOP [cyclophosphamide/doxorubicin/vincristine/prednisone] chemotherapy). Histopathologic analysis was performed when considered necessary.

RESULTS

After treatment, 4 of 5 patients (80%) who had CT-negative/PET-positive findings experienced relapse/progression, compared with only 1 of 22 patients (4.5%) in the CT-negative/PET-negative subset. Among the 18 patients with CT-positive findings, all 6 patients (100%) who had PET-positive findings experienced relapse or progression, compared with 1 of 12 patients (8.3%) who had PET-negative findings. The 2-year progression-free survival rates were 20% and 90% in the CT-negative/PET-positive and CT-positive/PET-negative subsets, respectively (P = 0.0031). During the follow-up, 2 patients, who presented a PET positivity with a negative CT scan, underwent a lymph node biopsy, which confirmed the presence of FL infiltration.

CONCLUSION

In patients with FL, persisting PET positivity is predictive of early disease progression, because it is still highly likely that patients with PET-negative findings will ultimately progress, but this has not yet been manifested during the period of observation.

Molecular Imaging of Proliferation in Malignant Lymphoma

We have determined the ability of positron emission tomography (PET) with the thymidine analogue 3'-deoxy-3'-[(18)F]fluorothymidine (FLT) to detect manifestation sites of malignant lymphoma, to assess proliferative activity, and to differentiate aggressive from indolent tumors. In this prospective study, FLT-PET was done additionally to routine staging procedures in 34 patients with malignant lymphoma. Sixty minutes after i.v. injection of approximately 330 MBq FLT, emission and transmission scanning was done. Tracer uptake in lymphoma was evaluated semiquantitatively by calculation of standardized uptake values (SUV) and correlated to tumor grading and proliferation fraction as determined by Ki-67 immunohistochemistry. FLT-PET detected a total of 490 lesions compared with 420 lesions revealed by routine staging. In 11 patients with indolent lymphoma, mean FLT-SUV in biopsied lesions was 2.3 (range, 1.2-4.5). In 21 patients with aggressive lymphoma, a significantly higher FLT uptake was observed (mean FLT-SUV, 5.9; range, 3.2-9.2; P < 0.0001) and a cutoff value of SUV = 3 accurately discriminated between indolent and aggressive lymphoma. Linear regression analysis indicated significant correlation of FLT uptake in biopsied lesions and proliferation fraction (r = 0.84; P < 0.0001). In this clinical study, FLT-PET was suitable for imaging malignant lymphoma and noninvasive assessment of tumor grading. Due to specific imaging of proliferation, FLT may be a superior PET tracer for detection of malignant lymphoma in organs with high physiologic fluorodeoxyglucose uptake and early detection of progression to a more aggressive histology or potential transformation.