Positron emission tomography (PET) for staging and evaluation of response to treatment in patients with Hodgkin's disease

A picture is worth a thousand words: a history of diagnostic imaging for lymphoma

The journey from early drawings of Thomas Hodgkin's patients to deep learning with radiomics in lymphoma has taken nearly 200 years, and in many ways, it parallels the journey of medicine. By tracing the history of imaging in clinical lymphoma practice, we can better understand the motivations for current imaging practices. The earliest imaging modalities of the 2D era each had varied, site-dependent sensitivity, and the improved accuracy of imaging studies allowed new diagnostic and therapeutic techniques. First, we review the initial imaging technologies that were applied to understand lymphoma spread and achieve practical guidance for the earliest lymphoma treatments. Next, in the 3D era, we describe how anatomical imaging advances replaced and complemented conventional modalities. Afterward, we discuss how the PET era scans were used to understand response of tumors to treatment and risk stratification. Finally, we discuss the emergence of radiomics as a promising area of research in personalized medicine. We are now able to identify involved lymph nodes and body sites both before and after treatment to offer patients improved treatment outcomes. As imaging methods continue to improve sensitivity, we will be able to use personalized medicine approaches to give targeted and highly focused therapies at even earlier time points, and ideally, we can obtain long-term disease control and cures for lymphomas.

Interim PET-results for prognosis in adults with Hodgkin lymphoma: a systematic review and meta-analysis of prognostic factor studies

BACKGROUND

Hodgkin lymphoma (HL) is one of the most common haematological malignancies in young adults and, with cure rates of 90%, has become curable for the majority of individuals. Positron emission tomography (PET) is an imaging tool used to monitor a tumour's metabolic activity, stage and progression. Interim PET during chemotherapy has been posited as a prognostic factor in individuals with HL to distinguish between those with a poor prognosis and those with a better prognosis. This distinction is important to inform decision-making on the clinical pathway of individuals with HL.

OBJECTIVES

To determine whether in previously untreated adults with HL receiving first-line therapy, interim PET scan results can distinguish between those with a poor prognosis and those with a better prognosis, and thereby predict survival outcomes in each group.

SEARCH METHODS

We searched MEDLINE, Embase, CENTRAL and conference proceedings up until April 2019. We also searched one trial registry (ClinicalTrials.gov).

SELECTION CRITERIA

We included retrospective and prospective studies evaluating interim PET scans in a minimum of 10 individuals with HL (all stages) undergoing first-line therapy. Interim PET was defined as conducted during therapy (after one, two, three or four treatment cycles). The minimum follow-up period was at least 12 months. We excluded studies if the trial design allowed treatment modification based on the interim PET scan results.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form according to the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Two teams of two review authors independently screened the studies, extracted data on overall survival (OS), progression-free survival (PFS) and PET-associated adverse events (AEs), assessed risk of bias (per outcome) according to the Quality in Prognosis Studies (QUIPS) tool, and assessed the certainty of the evidence (GRADE). We contacted investigators to obtain missing information and data.

MAIN RESULTS

Our literature search yielded 11,277 results. In total, we included 23 studies (99 references) with 7335 newly-diagnosed individuals with classic HL (all stages). Participants in 16 studies underwent (interim) PET combined with computed tomography (PET-CT), compared to PET only in the remaining seven studies. The standard chemotherapy regimen included ABVD (16) studies, compared to BEACOPP or other regimens (seven studies). Most studies (N = 21) conducted interim PET scans after two cycles (PET2) of chemotherapy, although PET1, PET3 and PET4 were also reported in some studies. In the meta-analyses, we used PET2 data if available as we wanted to ensure homogeneity between studies. In most studies interim PET scan results were evaluated according to the Deauville 5-point scale (N = 12). Eight studies were not included in meta-analyses due to missing information and/or data; results were reported narratively. For the remaining studies, we pooled the unadjusted hazard ratio (HR). The timing of the outcome measurement was after two or three years (the median follow-up time ranged from 22 to 65 months) in the pooled studies. Eight studies explored the independent prognostic ability of interim PET by adjusting for other established prognostic factors (e.g. disease stage, B symptoms). We did not pool the results because the multivariable analyses adjusted for a different set of factors in each study. Overall survival Twelve (out of 23) studies reported OS. Six of these were assessed as low risk of bias in all of the first four domains of QUIPS (study participation, study attrition, prognostic factor measurement and outcome measurement). The other six studies were assessed as unclear, moderate or high risk of bias in at least one of these four domains. Four studies were assessed as low risk, and eight studies as high risk of bias for the domain other prognostic factors (covariates). Nine studies were assessed as low risk, and three studies as high risk of bias for the domain 'statistical analysis and reporting'. We pooled nine studies with 1802 participants. Participants with HL who have a negative interim PET scan result probably have a large advantage in OS compared to those with a positive interim PET scan result (unadjusted HR 5.09, 95% confidence interval (CI) 2.64 to 9.81, I² = 44%, moderate-certainty evidence). In absolute values, this means that 900 out of 1000 participants with a negative interim PET scan result will probably survive longer than three years compared to 585 (95% CI 356 to 757) out of 1000 participants with a positive result. Adjusted results from two studies also indicate an independent prognostic value of interim PET scan results (moderate-certainty evidence). Progression-free survival Twenty-one studies reported PFS. Eleven out of 21 were assessed as low risk of bias in the first four domains. The remaining were assessed as unclear, moderate or high risk of bias in at least one of the four domains. Eleven studies were assessed as low risk, and ten studies as high risk of bias for the domain other prognostic factors (covariates). Eight studies were assessed as high risk, thirteen as low risk of bias for statistical analysis and reporting. We pooled 14 studies with 2079 participants. Participants who have a negative interim PET scan result may have an advantage in PFS compared to those with a positive interim PET scan result, but the evidence is very uncertain (unadjusted HR 4.90, 95% CI 3.47 to 6.90, I² = 45%, very low-certainty evidence). This means that 850 out of 1000 participants with a negative interim PET scan result may be progression-free longer than three years compared to 451 (95% CI 326 to 569) out of 1000 participants with a positive result. Adjusted results (not pooled) from eight studies also indicate that there may be an independent prognostic value of interim PET scan results (low-certainty evidence). PET-associated adverse events No study measured PET-associated AEs.

AUTHORS' CONCLUSIONS

This review provides moderate-certainty evidence that interim PET scan results predict OS, and very low-certainty evidence that interim PET scan results predict progression-free survival in treated individuals with HL. This evidence is primarily based on unadjusted data. More studies are needed to test the adjusted prognostic ability of interim PET against established prognostic factors.

Interim PET-results for prognosis in adults with Hodgkin lymphoma: a systematic review and meta-analysis of prognostic factor studies

BACKGROUND

Hodgkin lymphoma (HL) is one of the most common haematological malignancies in young adults and, with cure rates of 90%, has become curable for the majority of individuals. Positron emission tomography (PET) is an imaging tool used to monitor a tumour's metabolic activity, stage and progression. Interim PET during chemotherapy has been posited as a prognostic factor in individuals with HL to distinguish between those with a poor prognosis and those with a better prognosis. This distinction is important to inform decision-making on the clinical pathway of individuals with HL.

OBJECTIVES

To determine whether in previously untreated adults with HL receiving first-line therapy, interim PET scan results can distinguish between those with a poor prognosis and those with a better prognosis, and thereby predict survival outcomes in each group.

SEARCH METHODS

We searched MEDLINE, Embase, CENTRAL and conference proceedings up until April 2019. We also searched one trial registry (ClinicalTrials.gov).

SELECTION CRITERIA

We included retrospective and prospective studies evaluating interim PET scans in a minimum of 10 individuals with HL (all stages) undergoing first-line therapy. Interim PET was defined as conducted during therapy (after one, two, three or four treatment cycles). The minimum follow-up period was at least 12 months. We excluded studies if the trial design allowed treatment modification based on the interim PET scan results.

DATA COLLECTION AND ANALYSIS

We developed a data extraction form according to the Checklist for Critical Appraisal and Data Extraction for Systematic Reviews of Prediction Modelling Studies (CHARMS). Two teams of two review authors independently screened the studies, extracted data on overall survival (OS), progression-free survival (PFS) and PET-associated adverse events (AEs), assessed risk of bias (per outcome) according to the Quality in Prognosis Studies (QUIPS) tool, and assessed the certainty of the evidence (GRADE). We contacted investigators to obtain missing information and data.

MAIN RESULTS

Our literature search yielded 11,277 results. In total, we included 23 studies (99 references) with 7335 newly-diagnosed individuals with classic HL (all stages).Participants in 16 studies underwent (interim) PET combined with computed tomography (PET-CT), compared to PET only in the remaining seven studies. The standard chemotherapy regimen included ABVD (16) studies, compared to BEACOPP or other regimens (seven studies). Most studies (N = 21) conducted interim PET scans after two cycles (PET2) of chemotherapy, although PET1, PET3 and PET4 were also reported in some studies. In the meta-analyses, we used PET2 data if available as we wanted to ensure homogeneity between studies. In most studies interim PET scan results were evaluated according to the Deauville 5-point scale (N = 12).Eight studies were not included in meta-analyses due to missing information and/or data; results were reported narratively. For the remaining studies, we pooled the unadjusted hazard ratio (HR). The timing of the outcome measurement was after two or three years (the median follow-up time ranged from 22 to 65 months) in the pooled studies.Eight studies explored the independent prognostic ability of interim PET by adjusting for other established prognostic factors (e.g. disease stage, B symptoms). We did not pool the results because the multivariable analyses adjusted for a different set of factors in each study.Overall survivalTwelve (out of 23) studies reported OS. Six of these were assessed as low risk of bias in all of the first four domains of QUIPS (study participation, study attrition, prognostic factor measurement and outcome measurement). The other six studies were assessed as unclear, moderate or high risk of bias in at least one of these four domains. Nine studies were assessed as high risk, and three studies as moderate risk of bias for the domain study confounding. Eight studies were assessed as low risk, and four studies as high risk of bias for the domain statistical analysis and reporting.We pooled nine studies with 1802 participants. Participants with HL who have a negative interim PET scan result probably have a large advantage in OS compared to those with a positive interim PET scan result (unadjusted HR 5.09, 95% confidence interval (CI) 2.64 to 9.81, I² = 44%, moderate-certainty evidence). In absolute values, this means that 900 out of 1000 participants with a negative interim PET scan result will probably survive longer than three years compared to 585 (95% CI 356 to 757) out of 1000 participants with a positive result.Adjusted results from two studies also indicate an independent prognostic value of interim PET scan results (moderate-certainty evidence).Progression-free survival Twenty-one studies reported PFS. Eleven out of 21 were assessed as low risk of bias in the first four domains. The remaining were assessed as unclear, moderate or high risk of bias in at least one of the four domains. Eleven studies were assessed as high risk, nine studies as moderate risk and one study as low risk of bias for study confounding. Eight studies were assessed as high risk, three as moderate risk and nine as low risk of bias for statistical analysis and reporting.We pooled 14 studies with 2079 participants. Participants who have a negative interim PET scan result may have an advantage in PFS compared to those with a positive interim PET scan result, but the evidence is very uncertain (unadjusted HR 4.90, 95% CI 3.47 to 6.90, I² = 45%, very low-certainty evidence). This means that 850 out of 1000 participants with a negative interim PET scan result may be progression-free longer than three years compared to 451 (95% CI 326 to 569) out of 1000 participants with a positive result.Adjusted results (not pooled) from eight studies also indicate that there may be an independent prognostic value of interim PET scan results (low-certainty evidence).PET-associated adverse eventsNo study measured PET-associated AEs.

AUTHORS' CONCLUSIONS

This review provides moderate-certainty evidence that interim PET scan results predict OS, and very low-certainty evidence that interim PET scan results predict progression-free survival in treated individuals with HL. This evidence is primarily based on unadjusted data. More studies are needed to test the adjusted prognostic ability of interim PET against established prognostic factors.

Novel Biomarker Approaches in Classic Hodgkin Lymphoma

Classic Hodgkin lymphoma (cHL) is one of the most common lymphomas in the Western world. Advances in the management of cHL have led to high cure rates exceeding 80%. Nevertheless, relapse or refractory disease in a subset of patients and treatment-related toxicity still represents unsolved clinical problems. The introduction of targeted treatments such as PD-1 blockade and the CD30 antibody drug conjugate, brentuximab vedotin, has broadened treatment options in cHL, emphasizing the critical need to identify biomarkers with the goal to provide rationales for treatment selection, increase effective drug utilization, and minimize toxicity. The unique biology of cHL featuring low abundant tumor cells and numerous nonmalignant immune cells in the tumor microenvironment can provide various types of promising biomarkers related to the tumor cells directly, tumor microenvironment cross-talk, and host immune response. Here, we comprehensively review novel biomarkers including circulating tumor DNA and gene expression-based prognostic models that might guide the ideal management of cHL in the future.

The Impact of 18F-deoxyglucose Positron Emission Tomography on Tumor Staging, Treatment Strategy and Treatment Planning for Radiotherapy in a Department of Radiation Oncology

Aims and Background

The study analyzed the potential contribution of positron emission tomography (PET) in patient selection for radiotherapy and in radiation therapy planning.

Methods

Eighty-seven patients with a histological cancer diagnosis were accrued for the study from December 2000 to December 2001. Demographic characteristics included a median age of 54 years and male/female ratio of 51/36. All patients staged by conventional workup who were candidates for radiotherapy had PET imaging and were allocated to a conventional “pre/post-PET stage”. The treatment protocol and the shape and/or size of the portals was directly related to PET results. We examined 26 lung cancers, 15 gastrointestinal tumors, 22 genitourinary cancers and 24 hematologic malignancies.

Results

In the lung cancer group, the stage was modified in 10/26 patients (38.5%) by PET, with a change in management in 13 (50%) and a change in radiotherapy planning in 6 (23.1%). In the hematological group, stage was modified by PET in 8/24 cases (33.3%), with a change in treatment strategy in 9 (37.5%) and a change in radiotherapy planning in 3 (12.5%). In the gastrointestinal group, the stage was modified by PET in 2/15 cases (13.4%), with a change inn treatment strategy in 4 (26.7%) and a change in the decision for radiotherapy in 8 (no radiotherapy in 53.3%). In the mixed group (genitourinary, breast and other), the stage was modified by PET in 6/22 cases (27.3%), with a change in treatment strategy in 11 (50%) and a very low rate of change in radiotherapy planning.

Conclusions

PET contributed to a modification of stage in 26/87 patients (30%), to a changing in treatment strategy in 37/87 (42.5%), and to a substantial change of the shape and/or size of radiotherapy portals in 13/43 (30%) who underwent radiotherapy.

Current role of FDG PET/CT in lymphoma

The management approach in Hodgkin's (HL) and high-grade non-Hodgkin's lymphomas (NHL) has shifted towards reducing the toxicity and long-term adverse effects associated with treatment while maintaining favorable outcomes in low-risk patients. The success of an individualized treatment strategy depends largely on accurate diagnostic tests both at staging and during therapy. In this regard, positron emission tomography (PET) using fluorodeoxyglucose (FDG) with computed tomography (CT) has proved effective as a metabolic imaging tool with compelling evidence supporting its superiority over conventional modalities, particularly in staging and early evaluation of response. Eventually, this modality was integrated into the routine staging and restaging algorithm of lymphomas. This review will summarize the data on the proven and potential utility of PET/CT imaging for staging, response assessment, and restaging, describing current limitations of this imaging modality.

State-of-the-Art Research on "Lymphomas: Role of Molecular Imaging for Staging, Prognostic Evaluation, and Treatment Response"

Lymphomas are heterogeneous but potentially curable group of neoplasms. Treatment of lymphomas has rapidly evolved overtime with significant improvement in the cure rate and reductions in treatment-related toxicities. Despite excellent results, treatment programs are continued to be developed to achieve better curative and safety profiles. In these patients individualized therapy schemes can be devised based on a well-defined risk categorization. The therapy efficacy can be increased early during therapy in non-responding patients with escalated therapy protocols or with the addition of radiation therapy, particularly, in advanced-stage or unfavorable risk patients. The increasing availability of positron emission tomography using 18F-fluorodeoxyglucose, particularly fused with computed tomography (FDG-PET/CT) has lead to the integration of this modality into the routine staging and restaging for lymphoma with convincing evidence that it is a more accurate imaging modality compared with conventional imaging techniques. FDG-PET/CT is also is a promising surrogate for tumor chemosensitivity early during therapy. This review will summarize published data on the utility of FDG-PET/CT imaging in the staging, restaging, and predicting therapy response in patients with lymphoma.

Interim FDG-PET in Hodgkin lymphoma: a compass for a safe navigation in clinical trials?

Despite the rewarding results achieved in the treatment of Hodgkin lymphoma (HL), concerns have been raised regarding the long-term complications induced by therapy. Hence, the current challenge is to develop a new therapeutic strategy maintaining excellent patient outcome while reducing potentially life-threatening late adverse effects. Therefore, it would be beneficial to identify chemoresistant or refractory patients early during therapy for appropriate and timely escalation of treatment. Recently, compelling data have emerged on the prognostic role of interim [18F]-fluoro-2-deoxy-D-glucose positron emission tomography (FDG-PET) performed early during the course of treatment to predict ultimate outcome, even proving superior to conventional prognostic factors. Several ongoing prospective trials are exploring the feasibility of treatment de-escalation strategies in patients with a negative interim PET, as well as therapy escalation in advanced-stage HL patients who have a positive interim PET result. In this article, the published reports on the contribution of interim PET to the design of ongoing response-adapted clinical trials are reviewed. Moreover, some of the unresolved issues revolving around the suboptimal positive predictive value of interim PET are addressed with an emphasis on the interpretation criteria. A final remark on the appropriate use of interim PET is also provided.

PET-CT Imaging of Lymphoma

PET-CT is now the mainstay for imaging lymphoma patients. The complimentary nature of the metabolic and anatomic information provided by a PET-CT examination has become an essential component of patient management, complimenting clinical and laboratory criteria used in staging, restaging, and therapy monitoring. The nature of a particular lymphoma subtype and the patient’s clinical presentation will determine the extent PET-CT imaging is best employed in a particular patient’s management.

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.

The impact of functional imaging on radiation medicine

Radiation medicine has previously utilized planning methods based primarily on anatomic and volumetric imaging technologies such as CT (Computerized Tomography), ultrasound, and MRI (Magnetic Resonance Imaging). In recent years, it has become apparent that a new dimension of non-invasive imaging studies may hold great promise for expanding the utility and effectiveness of the treatment planning process. Functional imaging such as PET (Positron Emission Tomography) studies and other nuclear medicine based assays are beginning to occupy a larger place in the oncology imaging world. Unlike the previously mentioned anatomic imaging methodologies, functional imaging allows differentiation between metabolically dead and dying cells and those which are actively metabolizing. The ability of functional imaging to reproducibly select viable and active cell populations in a non-invasive manner is now undergoing validation for many types of tumor cells. Many histologic subtypes appear amenable to this approach, with impressive sensitivity and selectivity reported.

For clinical radiation medicine, the ability to differentiate between different levels and types of metabolic activity allows the possibility of risk based focal treatments in which the radiation doses and fields are more tightly connected to the perceived risk of recurrence or progression at each location.

This review will summarize many of the basic principles involved in the field of functional PET imaging for radiation oncology planning and describe some of the major relevant published data behind this expanding trend.

Fluorine-18 Fluorodeoxyglucose PET/CT Patterns of Extranodal Involvement in Patients with Non-Hodgkin Lymphoma and Hodgkin's Disease

Lymphoma may originate in extranodal sites. Extranodal lymphoma may also be secondary to and accompany nodal disease. Fluorine-18 fluorodeoxyglucose (18F-FDG) imaging has an essential role in the staging of lymphoma, in monitoring the response to therapy, and in detection of recurrence. The introduction of 18F-FDG PET/CT hybrid imaging allows for accurate localization of disease and may be specifically beneficial for the detection of unexpected extranodal sites of disease or exclusion of disease in the presence of nonspecific extranodal CT findings. Accurate staging and localization often dictate the appropriate treatment strategy in patients with lymphoma. Therefore, at any stage in the course of the disease, the potential presence of extranodal disease should be considered when interpreting 18F-FDG PET/CT studies in patients with non-Hodgkin lymphoma and Hodgkin's disease.

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.

Clinical impact of FDG-PET/CT in the planning of radiotherapy for early-stage Hodgkin lymphoma

BACKGROUND

Early-stage Hodgkin lymphoma (HL) has excellent survival rates but carries a high risk of late treatment-related adverse effects. Modern, individualised therapeutic strategies require an accurate determination of the extent of the disease. This study investigated the potential impact of 2-[18F]-fluoro-2-deoxy-d-glucose positron emission tomography/computerised tomogrpahy (FDG-PET/CT) in the planning of involved field radiotherapy (IFRT).

PATIENTS AND METHODS

Thirty patients received staging FDG-PET/CT before therapy, and IFRT after a short course of ABVD (adriamycin, bleomycin, vinblastine, dacarbazine) chemotherapy. IFRT planning was performed using only the CT data from the FDG-PET/CT scan. Later, the IFRT planning was performed anew using the FDG-PET/CT data as basis for contouring.

RESULTS

In 20 out of 30 patients, the radiotherapy (RT) course was unaffected by the addition of FDG-PET/CT. FDG-PET/CT would have increased the irradiated volume in seven patients where the volume receiving a minimum of 90% of the target dose was increased by 8-87%. FDG-PET/CT decreased the volume in two patients where the volume was reduced by 18% and 30%.

CONCLUSIONS

When used for RT planning, FDG-PET/CT results in larger IFRT treatment volumes. If FDG-PET/CT is introduced to RT planning, the method should be accompanied by a change in RT treatment strategy, aiming at more targeted therapy in order to best avoid radiation to normal tissues.

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.

Early positron emission tomography (PET) restaging: a predictive final response in Hodgkin's disease patients

BACKGROUND

It is important to distinguish between responders to standard treatment and non-responders Hodgkin's disease (HD) patients.

PATIENTS AND METHODS

Between June 2003-September 2004, in our institute, 40 newly-diagnosed patients with advanced stage HD were consecutively treated with ABVD chemotherapy for six cycles. All these patients underwent staging/restaging: computed tomography (CT) and positron emission tomography (PET) at time 0, PET after two cycles, CT and PET after four and six cycles.

RESULTS

After two cycles (PET-2), the PET was negative in 28/40 (70%), positive in 8/40 (20%), and minimal residual uptake (MRU) was present in the remaining four (10%) patients. After treatment, among eight patients who were PET-2+, seven showed refractory disease and one had relapse after 3 months. All four patients with MRU at the PET-2 became PET- during the further four cycles and, after treatment, three were in complete response (CR) and one relapsed after 5 months. All 28 PET negative patients at the PET-2 remained PET negative and all of them were in CR after treatment.

CONCLUSIONS

The PET use for early (after two cycles) response assessment in HD patients is a significant step forward and has the potential to help physicians make crucial decisions about further treatment.

Effect of drug-induced cytotoxicity on glucose uptake in Hodgkin's lymphoma cells

BACKGROUND

In Hodgkin's lymphoma, F-18-fluoro-deoxy-d-glucose positron emission tomography (FDG-PET) is used for staging and response evaluation after chemotherapy. However, drug-mediated downregulation of glucose uptake in viable Hodgkin's lymphoma cells might limit the use of FDG-PET.

METHODS

We analyzed the effect of etoposide on cell viability and uptake of F-18-fluoro-deoxy-D-glucose or the glucose analog 2-[N-(7-nitrobenz-2-oxa-1,3-diazol-4-yl)amino]-2-deoxyglucose (2-NBDG) in vitro.

RESULTS

Etoposide induced a dose-dependent cytotoxicity in HDLM-2 cells which was significantly correlated with reduced FDG uptake. However, it also significantly increased the portion of viable cells which did not take up 2-NBDG. Interestingly, etoposide-induced cytotoxicity was mainly mediated via caspase-dependent mechanisms, whereas the cell death induced by deprivation of glucose was mediated via caspase-independent mechanisms.

CONCLUSION

Etoposide-mediated reduction of glucose uptake by Hodgkin's lymphoma cells is mainly caused by cell death. In a small fraction of viable cells, etoposide might downregulate glucose transporters and/or hexokinase activity and by that inhibit glucose uptake. This, however, might not lead to false-negative results of response evaluation in Hodgkin's lymphoma patients after chemotherapy, because inhibition of glucose uptake itself seems to be a strong inducer of cell death. Altogether, this study provides important in vitro evidence to clarify the mechanisms by which FDG-PET monitors the effect of anti-cancer treatment in Hodgkin's lymphoma patients.

Positron emission tomography imaging for lymphoma

PURPOSE OF REVIEW

To review the current role and the limitations of F-fluorodeoxygenase positron emission tomography in the management of lymphoma, with a particular focus on studies published since January 2004.

RECENT FINDINGS

F-fluorodeoxygenase positron emission tomography should be routinely performed at the initial diagnosis of patients with suffering from Hodgkin's disease because it adds useful informations to conventional staging techniques. Residual F-fluorodeoxygenase uptake is an important prognostic factor after one or a few cycles of chemotherapy, but it is clearly too early to change patient treatment on the basis of F-fluorodeoxygenase positron emission tomography results. F-fluorodeoxygenase positron emission tomography is the best noninvasive imaging technique after treatment; however, it is always indicated to correlate positron emission tomography findings with clinical data, other imaging modalities, a biopsy, or all three to reduce the risk of false positive results. There are some concerns about the positive predictive value of positron emission tomography after treatment, especially in childhood lymphoma. Clinicians should be aware of positron emission tomography findings in specific clinical conditions in this patient population. F-fluorodeoxygenase positron emission tomography combined with computed tomography offers advantages over the two used separately and read side by side. It may be particularly useful for the planning of radiation therapy or for the planning of a surgical biopsy. Several studies have shown that F-fluorodeoxygenase positron emission tomography is definitively superior to Ga scintigraphy. New radiotracers such as F-fluorothymidine may be useful for the noninvasive assessment of proliferation in vivo.

SUMMARY

F-fluorodeoxygenase positron emission tomography has become the most important nuclear medicine imaging modality in the field of lymphoma. It should be routinely used in the treatment of lymphoma patients.

Comparison of 18F-FDG-PET and standard procedures for the pretreatment staging of children and adolescents with Hodgkin's disease

PURPOSE

The aim of this study was to perform a prospective, blinded comparison of( 18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) and conventional staging methods (CSMs) for initial staging of children and adolescents with Hodgkin's disease (HD).

METHODS

Over a period of 4 years, 55 children and adolescents with HD (mean age 15.5 years, range 3.9-18.9 years) were prospectively recruited into the study. They underwent 61 FDG-PET studies using a dedicated whole-body PET scanner as a part of their initial staging work-up. PET findings were correlated with the results of CSMs, including computed tomography (CT), ultrasound, bone scanning and bone marrow examination. Discordant findings were resolved by magnetic resonance imaging or clinical follow-up (range 2-47 months).

RESULTS

PET correctly changed the staging in 15% of patients (seven upstagings, two downstagings). Only two out of 61 patients (3%) were not accurately staged by PET; in these children, PET missed small lymphoma nodules detected on lung CT. The sensitivity of PET and CSMs for pretreatment staging was 96.5% and 87.5%, respectively; specificity was 100% and 60%, and accuracy, 96.7% and 85.2%, respectively. Upon combination of FDG-PET and lung CT, the diagnostic accuracy reached 100% in our series.

CONCLUSION

Our study showed that whole-body FDG-PET is an efficient and useful method for the initial staging of children with HD. FDG-PET in combination with lung CT should be recommended as a screening method prior to other conventional imaging modalities to plan a rational staging protocol. Large multicentre prospective studies are necessary to verify this conclusion.

Different histopathological subtypes of Hodgkin lymphoma show significantly different levels of FDG uptake

Positron emission tomography using 2-[18F]fluoro-2-deoxy-D-glucose (FDG-PET) enables quantitative analysis of metabolic activity. This study investigated standardized uptake value (SUV) levels in the different histopathological subtypes of Hodgkin lymphoma (HL). Sixty patients with newly diagnosed HL underwent staging FDG-PET/CT after lymph node biopsy. Maximum SUV in each patient (SUV(max/total)) and in each affected region or organ (SUV(max)) were recorded. Mean SUV(max/total) was 9.3 g/ml in seven nodular lymphocyte predominance (NLP) patients, 16.3 g/ml in 38 nodular sclerosis (NS) patients, 20.8 g/ml in 11 mixed cellularity (MC) patients, and 19.5 g/ml in four patients with unclassified classical HL (CHL-NOS), (ANOVA, p = 0.011). Out of 780 sites (600 lymph node regions plus 180 organs), 208 sites were found to be affected with HL. Mean SUV(max) was 8.3 g/ml in the 12 sites with NLP, 11.2 g/ml in the 147 sites affected with NS, 14.6 g/ml in the 36 sites with MC, and 13.1 g/ml in the 13 sites with CHL-NOS (ANOVA, p = 0.002). There is a significant difference in FDG/glucose uptake between the different histopathological subtypes of HL.

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.

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%.

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.

Addition of 18F-FDG-PET scans to radiotherapy planning of thoracic lymphoma

BACKGROUND AND PURPOSE

FDG-PET possesses greater sensitivity and accuracy than computed tomography (CT) in detecting diseased lymph nodes. Though the FDG-PET scans are acquired for similar diagnostic reasons as CT, they are not used in the radiotherapy (RT) planning process. Successful tumourcidal dose is usually delivered but large volumes of normal and non-malignant tissues are irradiated due to the nature of lymphoma and also to the subjectivity of the field determining process. This study tries to lessen the subjectivity of the field determining process by the addition of currently acquired PET to the conventional thoracic lymphoma RT. The differences between retrospectively delineated volumes from CT and FDG-PET were compared and the effect of this additional information was evaluated.

MATERIALS AND METHODS

Seventeen FDG-PET scans were registered to corresponding CT scans using rigid-body registration with negligible intra-observer variability. Comparisons were made between the volumes, lateral extensions and the most inferior point of the delineated gross tumour volumes (GTVs).

RESULTS

For 1/17 patient data, no diseased volumes were delineated and in 6/17, no volumes were delineated on PET and yet in CT, masses up to 367.2 cm3 were outlined. From the 10 positive-CT and PET data, the GTV(PET) were smaller than GTV(CT) in six cases. Greater than 3.0 cm lateral disease extension differences were observed in 4/10 cases. Inferior tumour extents were confirmed in 6/10 cases whereas in 2/10 patients GTV(CT) was greater than 12.0 cm inferior compared to GTV(PET).

CONCLUSIONS

FDG-PET data can be introduced to current thoracic lymphoma RT planning protocol with minimal intervention and changes. The subjectivity in the RT planning of thoracic lymphoma would be decreased with the addition of currently acquired FDG-PET data.

A Consensus Protocol: Image-improved Therapeutic Guidelines for Limited Adult Hodgkin's Disease

Hodgkin's disease (HD) has greatly benefited from new technologies in terms of less invasive and more accurate staging as well as improved overall and relapse-free survival. However, the likelihood of late adverse effects of treatment, including second tumors, has increased due to the longer survival of patients with HD. Today's trend is to aim at minimal therapeutic exposure while guaranteeing lower therapy-related morbidity. This encourages new research efforts but also leads to less uniformity in treatments, as observed in the Veneto Region in Italy. The Gruppo Veneto Linfomi, composed of representatives of Radiotherapy and Oncology Departments of the Veneto Region, has been analyzing this problem and proposing therapy guidelines since 1995. A set of 10 prognostic factors has been developed to identify three prognostic groups: highly favorable (HF) are patients up to 40 years of age presenting with stage I disease involving only one site of disease with a maximum tumor diameter (TD) of 5 cm and no adverse factors. In this group only mantle field irradiation is recommended if the disease is located in the neck or above, inverted-Y irradiation is recommended for distal subdiaphragmatic lesions, and subtotal nodal irradiation in all other cases. HF cases may also be treated like favorable cases with limited chemoradiation. Favorable (F) cases are patients in stage I with a TD greater than 5 cm and smaller than 10 cm or stage II, up to three sites of disease and negative prognostic factors for systemic disease. All other patients are included in the “not favorable” (NF) group at Ann Arbor stage I or II with any adverse prognostic factor. For the latter two groups, chemotherapy with the ABVD or Stanford V regimen precedes involved-field radiotherapy to sites with a TD of at least 5 cm. The total irradiation dose is determined by local disease extent and level of response to chemotherapy. Images on which the radiation fields are drawn serve as an important reference to improve the homogeneity of treatments. This protocol includes a list of adverse treatment effects (chemo- and/or radiotherapy) together with follow-up guidelines for the early detection of secondary cancers in previously irradiated patients.

FDG-PET in the clinical management of Hodgkin lymphoma

Positron emission tomography (PET) is a molecular functional imaging technique that provides qualitative and quantitative information about the localization and activity of pathophysiological processes. The most commonly used tracer for oncological purposes is 2-[18F]fluoro-2-deoxy-d-glucose (FDG). FDG-PET has within recent years become the most important nuclear medicine imaging modality in the management of lymphoma. This review summarizes the data published so far concerning the value of FDG-PET in staging, treatment monitoring, therapy planning, and follow-up of Hodgkin lymphoma (HL). FDG-PET detects more disease sites and involved organs than conventional staging procedures including computerized tomography (CT) and has a large influence on staging. FDG-PET during and after therapy appears to provide considerable prognostic information. However, the impact on patient outcome is not clear since no controlled trials are conducted and follow-up periods are generally short. The value of dual-modality PET/CT and its potential role in the radiotherapy planning is discussed.

18p-FDG PET is superior to67Ga SPECT in the staging of non-Hodgkin’s lymphoma

OBJECTIVE

Our study aims to compare diagnostic accuracy between 18F-FDG PET and 67Ga SPECT in the staging of non-Hodgkin's lymphoma.

METHODS

Twenty-eight patients with non-Hodgkin's lymphoma, underwent 18F-FDG PET, 67Ga SPECT and CT for the pretreatment staging of malignant lymphoma between August 1999 and March 2002. 18F-FDG PET imaging was obtained 60 minutes after the intravenous administration of 185 MBq of 18F-FDG. 67Ga SPECT imaging was obtained 2 days after the intravenous administration of 148 MBq of 67Ga. 18F-FDG PET and 67Ga SPECT were performed within one month. Both imagings were performed on the area from the neck to the pelvis. The 18F-FDG PET and 67Ga SPECT findings were compared with the CT findings and the clinical course.

RESULTS

Sixty-six nodal lesions were clinically confirmed. Of these, 32 were identified by both 18F-FDG PET and 67Ga SPECT. The remaining 34 lesions were identified only by 18F-FDG PET. The mean (+/- SD) sizes' of the nodes were 34.7 +/- 32.4 mm for 18F-FDG-positive and 67Ga-positive lesions and 15.7 +/- 8.3 mm for 18F-FDG-positive and 67Ga-negative lesions (p < 0.001). Of the 23 extranodal lesions, 12 were identified by both 18F-FDG PET and 67Ga SPECT, whereas 6 lesions were identified by only 18F-FDG PET. Five lesions were not identified by either technique. No 18F-FDG-negative but 67Ga-positive nodal or extranodal lesions were observed. The difference in findings between the two studies is related to the difference in the size but not in the histology or site of the lesions.

CONCLUSION

18F-FDG PET detected significantly more lesions particularly small lesions than 67Ga SPECT. Thus, 18F-FDG PET is considered to be superior to 67Ga SPECT in the staging of non-Hodgkin' s lymphoma.

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.

Positron emission tomography in patients with Hodgkin's disease: correlation to histopathologic subtypes

The aim of this study was to evaluate the initial staging and restaging of Hodgkin's disease (HD) according to histopathologic subtype (HST) using fluorine-18-deoxyglucose-positron emission tomography (PET). Special attention was paid to the accuracy of PET for detection of bone marrow infiltration (BMI). 44 patients with HD (m:f = 28:16, mean age 36 +/- 15 years) underwent PET; 16 were primary stagings and 28 restaging examinations. PET results were compared with methods of conventional staging including computed tomography (CT) and bone marrow biopsy. Viable tumor tissue was detected by PET in 25/44 cases, 16 nodular sclerosis (NS), 4 mixed cellularity (MC), 3 lymphocyte predominance (LP) and 2 cases with a nonclassified subtype (NC). FDG tumor uptake, measured as standard uptake value (SUV), ranged from 1.7 to 13. Maximum SUV in NS was 5.2 +/- 1.5 (2.5-7.3), 3.2 +/- 2.4 for MC, 2.6 +/- 0.7 for LP, and 9.1 +/- 3.8 for NC, respectively. In 7% of all patients (3/44) bone marrow infiltrations were detected by PET. PET is known for its superior detection of viable tissue in HD. In this study it was shown that HST does not influence the intensity of glucose metabolism, although 2 patients with NC showed the highest SUVs. In addition PET accurately detected focal BMI and may thus be applied before BMB to guide its optimal use.

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.

Hodgkin's lymphoma

Hodgkin's lymphoma was first described in 1832, but the nature of the pathognomic Reed-Sternberg cell, on which diagnosis of the disease is based, has only been elucidated in the past few years. Radiotherapy has been used to treat localised disease since the 1940s, and in the 1960s, effective combination chemotherapy regimens were introduced for anatomically advanced disease. The past three decades have witnessed continued improvement in outcome to such an extent that Hodgkin's lymphoma is now one of the most curable of all non-cutaneous malignancies. With improved survival and extended follow-up, relevance of treatment-induced late effects has become apparent, and modern therapeutic strategies must fully account for these effects. We review the pathology of Hodgkin's lymphoma, and its clinical presentation, investigation, present management, and natural history, including late effects of treatment.

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.

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.

Comparison of fluorine-18 fluorodeoxyglucose positron emission tomography and Ga-67 scintigraphy in evaluation of lymphoma

BACKGROUND

The accuracy of fluorodeoxyglucose positron emission tomography (FDG-PET; dual-head camera with attenuation correction) and Ga-67 scintigraphy was compared to identify disease sites in patients with Hodgkin disease (HD) and intermediate and high-grade non-Hodgkin lymphoma (NHL) at initial diagnosis or clinical recurrence.

METHODS

Fifty-one contemporaneous FDG-PET and Ga-67 scintigraphies were performed on patients with NHL (35 intermediate grade, 3 high grade) or HD (13 patients). Sites of disease were correlated on a site-by-site basis on FDG-PET and Ga-67 images. Tumor-to-background (T/B) ratios were obtained for both techniques. Discordant FDG-PET and Ga-67 findings were correlated with computed tomography findings or clinical evaluation including repeat FDG-PET scans obtained after therapy.

RESULTS

Fluorodeoxyglucose positron emission tomography was positive at all 158 sites in 51 patients compared with 113 sites in 41 positive studies with Ga-67 scintigraphy (single positron emission computed tomography [SPECT] and/or planar images). In 44 patients who had complete Ga-67 SPECT data on all tumor sites, FDG-PET was positive at 126 sites and Ga-67 SPECT was positive at 81 sites. Ga-67 SPECT failed to demonstrate disease at 45 sites (35.7%). In 10 of 44 patients, Ga-67 SPECT completely failed to detect any disease at 22 of 45 sites (17.5%) and partially identified disease sites at 23 of 45 sites (18.2%) in 11 patients regardless of the tumor site and histology. In these patients, the lesions measured between 0.6 and 14.0 cm by CT. Fluorodeoxyglucose positron emission tomography revealed higher stage disease in 13 patients compared with Ga-67 imaging. Tumor-to-background ratios were statistically different between the two techniques with higher ratios obtained with FDG-PET (P < 0.0001).

CONCLUSIONS

In imaging aggressive lymphoma and HD before therapy, FDG-PET has significantly higher site and patient sensitivity than Ga-67 scintigraphy (100% vs. 71.5% and 100% vs. 80.3%, respectively). The change in disease stage by FDG-PET may result in a change in therapy strategy.

Thoracic positron emission tomography using18F-fluorodeoxyglucose for the evaluation of residual mediastinal Hodgkin disease

Residual mediastinal masses are frequently observed in patients with Hodgkin disease (HD) after completed therapy, and the discrimination between active tumor tissue and fibrotic residues remains a clinical challenge. We studied the diagnostic value of metabolic imaging by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in detecting active mediastinal disease and predicting relapse. Twenty-eight HD patients with a residual mediastinal mass of at least 2 cm after initial therapy or after salvage chemotherapy were prospectively assigned to 29 examinations with FDG PET and were evaluated as 29 “subjects.” Patients were monitored for at least 1 year after examination and observed for signs of relapse. Median follow-up was 28 months (range, 16 to 68 months). A PET-negative mediastinal tumor was observed in 19 subjects, of whom 16 stayed in remission and 3 relapsed. Progression or relapse occurred in 6 of 10 subjects with a positive PET, whereas 4 subjects remained in remission. The negative predictive value (negative PET result and remission) at 1 year was 95%, and the positive predictive value (positive PET result and relapse) was 60%. The disease-free survival for PET-negative and PET-positive patients at 1 year was 95% and 40%, respectively. The difference was statistically significant. A negative FDG PET indicates that an HD patient with a residual mediastinal mass is unlikely to relapse before 1 year, if ever. On the other hand, a positive PET result indicates a significantly higher risk of relapse and demands further diagnostic procedures and a closer follow-up.

Thoracic positron emission tomography using 18F-fluorodeoxyglucose for the evaluation of residual mediastinal Hodgkin disease

Residual mediastinal masses are frequently observed in patients with Hodgkin disease (HD) after completed therapy, and the discrimination between active tumor tissue and fibrotic residues remains a clinical challenge. We studied the diagnostic value of metabolic imaging by 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in detecting active mediastinal disease and predicting relapse. Twenty-eight HD patients with a residual mediastinal mass of at least 2 cm after initial therapy or after salvage chemotherapy were prospectively assigned to 29 examinations with FDG PET and were evaluated as 29 "subjects." Patients were monitored for at least 1 year after examination and observed for signs of relapse. Median follow-up was 28 months (range, 16 to 68 months). A PET-negative mediastinal tumor was observed in 19 subjects, of whom 16 stayed in remission and 3 relapsed. Progression or relapse occurred in 6 of 10 subjects with a positive PET, whereas 4 subjects remained in remission. The negative predictive value (negative PET result and remission) at 1 year was 95%, and the positive predictive value (positive PET result and relapse) was 60%. The disease-free survival for PET-negative and PET-positive patients at 1 year was 95% and 40%, respectively. The difference was statistically significant. A negative FDG PET indicates that an HD patient with a residual mediastinal mass is unlikely to relapse before 1 year, if ever. On the other hand, a positive PET result indicates a significantly higher risk of relapse and demands further diagnostic procedures and a closer follow-up.

Can positron emission tomography with [(18)F]-fluorodeoxyglucose after first-line treatment distinguish Hodgkin's disease patients who need additional therapy from others in whom additional therapy would mean avoidable toxicity?

To assess the ability of restaging positron emission tomography (PET) scanning to predict clinical outcome after first-line treatment in patients with Hodgkin's disease, we included 60 patients with histologically proven HD, who underwent whole-body [(18)F]-fluorodeoxygenase ([(18)F]-FDG)-PET studies after first-line treatment and with a follow-up of at least 1 year. Persistence or absence of residual disease on PET was related to progression-free survival (PFS) using Kaplan-Meier survival analysis. After treatment, 55 patients showed a normal [(18)F]-FDG-PET scan; 50 of 55 remained in complete remission (CR), with a median follow-up of 955 d. Only five patients relapsed (median PFS, 296 d). During follow-up in all five patients, [(18)F]-FDG-PET was the first tool that became positive for relapse. Persistent abnormal [(18)F]-FDG uptake was seen in only five patients; all of them relapsed (median PFS, 296 d). In four of five patients, only PET predicted persistent disease. All relapses were proven histologically. Two-year actuarial PFS rate for negative patients was 91% compared with 0% for positive patients. We concluded that [(18)F]-FDG-PET has an important prognostic role in the post-treatment evaluation of HD patients.

The value of Ga-67 scintigraphy and F-18 fluorodeoxyglucose positron emission tomography in staging and monitoring the response of lymphoma to treatment

Gallium-67 scintigraphy (GS) has the ability to provide important diagnostic and prognostic information for the evaluation of patients with lymphoma. GS is superior to morphologic imaging techniques because of its affinity to viable lymphoma cells. The value of GS lies not in the initial diagnosis but primarily in assessing the results of treatment and in the follow-up of patients with lymphoma. Nevertheless, GS has not gained the expected wide acceptance, possibly because of the meticulous technique required and the expertise needed for optimal interpretation. The introduction of positron emission tomography (PET) with F-18 fluorodeoxyglucose (FDG) as a tumor-seeking agent, which provides images of superior quality, may have an impact on the current role of GS in the management of patients with lymphoma. FDG-PET seems to share with GS the advantages of a tumor viability agent. It appears to be more sensitive for detecting nodal and extranodal sites of disease than GS and may have predictive value during and after therapy for lymphoma. These potential clinical and economic advantages of FDG-PET need to be confirmed in systematic, large-scale prospective studies.

Pitfalls in imaging Hodgkin's disease with computed tomography and positron emission tomography using fluorine-18-fluorodeoxyglucose

We report on a patient with Hodgkin's disease who presented with hypodense splenic lesions and corresponding increased glucose metabolism in FDG-PET imaging, four months after completion of initial treatment, suggestive of early relapse. Serological testing for toxoplasma gondii, however, showed evidence of a recently reactivated or newly acquired infection. Three weeks after immediate antibiotic treatment with Daraprime and Sulfadiazin, the splenic lesions had completely resolved. Additionally, serological titers for toxoplasma gondii were normalized and whole body FDG-PET imaging showed no metabolic activity. Although the positive predictive value of PET imaging to indicate lymphoma is reported to be higher than CT, hypermetabolic lesions are not specific for malignant tissue. Whereas benign tumors typically show low glucose metabolism, activated granulocytes and macrophages may display significantly increased glucose consumption. In conclusion, our case report shows that although therapeutic decisions are often based on the results of imaging modalities, the taking of a detailed history and the acquisition of histological confirmation of the suspected lymphoma relapse are also advisable where possible. Cellular immunodeficiency can result in severe infections even in patients with intermediate stage Hodgkin's lymphoma in remission after combined modality treatment. Therefore, despite the high sensitivity of FDG-PET imaging for the detection of recurrent lymphoma, the differential diagnosis of infectious lesions should be kept in mind, in particular in immunocompromised patients.

Accumulation of sestamibi in lymphoma cell lines in vitro

Although some authors have suggested that sestamibi imaging is useful in evaluation of patients with lymphoma, others have obtained equivocal results. This discrepancy has been further investigated in vitro using two patient-derived non-Hodgkin's lymphoma cell lines, OCI-Ly3 and OCI-Ly18. Sestamibi (0.2 MBq/ml) was added to a suspension of OCI-Ly3 or OCI-Ly18 cells and aliquots were removed over 1 h and centrifuged to determine cell-associated radioactivity. Further experiments studied the effect of addition of a P-glycoprotein (Pgp) modulator or alteration in plasma and/or mitochondrial membrane potentials. Accumulation of sestamibi reached plateau values within 30 min, but these values were 6-fold higher in OCI-Ly3 than in OCI-Ly18. Inhibition of Pgp function with GG918 or PSC833 did not affect OCI-Ly3 cells but increased accumulation in OCI-Ly18 cells 3-fold, indicating a moderate level of Pgp. However, both cell lines responded similarly to membrane potential alterations: hyperpolarization of the mitochondrial membrane with nigericin had little effect on accumulation: in contrast, depolarization of the plasma membrane with an isotonic high potassium buffer reduced accumulation of sestamibi to 52% of control and additional depolarization of the mitochondrial membrane with valinomycin further reduced accumulation to 12% of control levels. These studies suggest that there can be wide differences in accumulation between cell lines, in part due to Pgp-mediated efflux, but that both of these cell lines have highly polarized mitochondria with little further capacity for hyperpolarization.