Positron Emission Tomography Using 18F-Fluorodeoxyglucose for the Evaluation of Residual Hodgkin's Disease Mediastinal Masses

Altered glycolysis results in drug-resistant in clinical tumor therapy

Cancer cells undergo metabolic reprogramming, including increased glucose metabolism, fatty acid synthesis and glutamine metabolic rates. These enhancements to three major metabolic pathways are closely associated with glycolysis, which is considered the central component of cancer cell metabolism. Increasing evidence suggests that dysfunctional glycolysis is commonly associated with drug resistance in cancer treatment, and aberrant glycolysis plays a significant role in drug-resistant cancer cells. Studies on the development of drugs targeting these abnormalities have led to improvements in the efficacy of tumor treatment. The present review discusses the changes in glycolysis targets that cause drug resistance in cancer cells, including hexokinase, pyruvate kinase, pyruvate dehydrogenase complex, glucose transporters, and lactate, as well the underlying molecular mechanisms and corresponding novel therapeutic strategies. In addition, the association between increased oxidative phosphorylation and drug resistance is introduced, which is caused by metabolic plasticity. Given that aberrant glycolysis has been identified as a common metabolic feature of drug-resistant tumor cells, targeting glycolysis may be a novel strategy to develop new drugs to benefit patients with drug-resistance.

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.

Evolving Role of PET-Based Novel Quantitative Techniques in the Management of Hematological Malignancies

"The role of ¹⁸F-fluorodeoxyglucose PET/computed tomography in hematological malignancies continues to expand in disease diagnosis, staging, and management. A key advantage of PET over other imaging modalities is its ability to quantify tracer uptake, which can be used to determine degree of disease activity. Although tracer uptake with PET is conventionally measured in focal lesions, novel quantitative techniques are being investigated that set objective protocols and produce robust parameters that represent total disease activity portrayed by PET. This article discusses recent advances in PET quantification that can improve reliability and accuracy of characterizing hematological malignancies."

Role of FDG PET-CT in the treatment management of Hodgkin lymphoma

Fluorodeoxyglucose (FDG) positons emission tomography (PET)-computed tomography (CT) is used in many ways at baseline and during the treatment of patients with Hodgkin lymphoma. Many properties of the technique are used in the different steps of patient's management. Initial staging with PET-CT is more accurate than conventional imaging and PET-CT also became the gold standard imaging at the end of treatment with a negative PET-CT mandatory for reaching a complete remission. Early assessment of response by PET-CT is one of the most powerful prognostic factors for progression-free survival of patients with localized and advanced stages and allows guiding treatment. Conversely, previous studies showed that there is no role of FDG PET-CT for the patient's follow-up.

Comparison of various criteria in interpreting end of therapy F-18 labeled fluorodeoxyglucose positron emission tomography/computed tomography in patients with aggressive non-Hodgkin lymphoma

Various interpretation criteria exist to assess end of therapy F-18 labeled fluorodeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) in lymphoma. This study was carried out to compare these criteria. Data of 69 patients with aggressive non-Hodgkin lymphoma (AGR-NHL) who underwent FDG PET/CT at the end of therapy and were followed up for a minimum period of 1 year (median follow-up period 17 months) were evaluated. Twenty-eight of the 69 patients were found to have residual/recurrent disease during follow-up. The accuracy for predicting residual disease of International Harmonization Project (IHP) criteria, London criteria and Gallamini criteria was 71.0%, 84.0% and 88.4%, respectively. Gallamini and London criteria had greater accuracies in predicting residual disease than IHP criteria (p = 0.0001). The major difference in accuracy was due to the low positive predictive value of IHP criteria. Positive predictive values (PPVs) of both London and Gallamini criteria (79.3% and 88.5%, respectively) were high when compared with that of IHP criteria (60.5%) (p = 0.001). Negative predictive values (NPVs) were similar for all the criteria. In conclusion, Gallamini and London criteria had higher accuracy when interpreting end of therapy FDG PET/CT studies in AGR-NHL. London criteria can be used preferentially over Gallamini criteria because of simplicity in interpretation and reproducibility.

Positron Emission Tomography in the Management of Hodgkin Lymphoma

Accurate imaging of lymphoma is essential for optimal management. Positron emission tomography (PET), by providing both anatomic and functional information, is fundamentally altering staging, monitoring of response, response assessment, and choice of treatment modality for lymphomas, including Hodgkin lymphoma. This imaging technique, when used carefully in conjunction with standard testing, increases the sensitivity of lesion detection, provides an opportunity to monitor the quality of response during treatment, permits separation of fibronecrotic scar tissue from viable tumor, and adds prognostic information. PET has become integral to modern lymphoma management, but as a relatively new diagnostic technique, it is still being studied and neither its full potential nor its major limitations are fully understood. Discussed herein are recent observations from clinical trials and single-center experiences with PET to explore its advantages and limitations from a clinician's point of view.

[Prognostic value of FDG-PET in Hodgkin lymphoma for posttreatment evaluation. Long-term follow-up results]

In the past few decades Hodgkin lymphoma (HL) has become a highly curable malignant disease, as a result of using modern polychemotherapy and irradiation. Differentiation of active tumor from fibrosis or necrosis within residual radiographic masses represents a problem of interpretation.

AIMS

The aim of this retrospective study is to assess the value of FDG-PET for prediction of remission or relapse in HL.

PATIENTS AND METHODS

Data of 128 patients, who had residual masses on CT after completion of their planned treatment, have been analyzed. FDG-PET was performed between January 1995 and February 2005.

RESULTS

The median duration of the follow-up from PET was 75.5 months (range: 20-180 months). 89 (70%) patients had negative and 39 (30%) patients had positive FDG-PET results. The numbers of true-positive, true-negative, false-positive and false-negative subjects were 29, 83, 10 and 6, respectively. Sensitivity of post-treatment FDG-PET was 83%, specificity 93%, positive predictive value 74%, negative predictive value 93%, and accuracy 88%. The difference between the event free survival of PET positive and negative cases is highly significant (p = 0.0000), according to the Mantel-Cox test.

CONCLUSION

Our results, in accordance with literature, clearly indicate that patients with negative FDG-PET results are unlikely to progress or relapse during a long follow-up. However, false positive uptake is a problem. We have investigated the effect of age, histological subtype, clinical stage and the type of treatment on the accuracy, but on the basis of these facts we could not find any significant difference. However, the date of the investigation influenced the results: before 2000 the number of false results was significantly higher than after that time, which shows the importance of investigators' experience.

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.

Hodgkin lymphoma: Response assessment by Revised International Workshop Criteria

Until recently, response assessment in patients with Hodgkin's lymphoma (HL) 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) has a higher sensitivity and specificity compared with that of CT, and Revised International Workshop Criteria (IWC + PET) were recently proposed, which combine both imaging techniques. We determined whether these integrated IWC + PET-criteria can more accurately predict outcome compared with IWC-criteria in 56 patients with HL. Of the original 56 patients, nine patients relapsed and 47 are still in remission after a median follow-up of 9 years. Based on IWC-criteria, 15 patients had a complete remission (CR) after chemotherapy, 20 had complete remission unconfirmed (CRu), 19 had partial remission (PR) and two had stable disease (SD). In comparison, by IWC + PET, 47 had CR, seven had PR and two had SD. For IWC, outcome was not significantly different in patients with CR/CRu compared to PR (P = 0.61), while for IWC + PET criteria, time-to-next-treatment was significantly shorter in patients with PR compared to CR (P = 0.01). Therefore, IWC + PET-guidelines provide a more accurate response classification compared with that of IWC-guidelines, and are the preferred method for response assessment in patients with Hodgkin's lymphoma.

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.

FDG PET scan strategies and long-term outcomes after first-line therapy in Hodgkin's disease

BACKGROUND

The use of positron emission tomography with fluoro-deoxy-glucose (FDG PET) in Hodgkin's disease (HD) is continuing to expand worldwide, with response assessment after completion of therapy being its most widely utilized application. A positive scan has been associated with high relapse rates and disease progression.

METHODS

A decision analysis was performed to determine the long-term impact of FDG PET restaging both with and without computed tomography (CT) in terms of the 5-year progression-free survival (5yrPFS). Outcomes and utilities were based on published data. The first strategy involved CT restaging after first-line therapy, with or without subsequent FDG PET, while the second strategy used FDG PET scan alone. All positive test required histological examination. Upon histological confirmation of active lymphoma, patients were considered candidates for autologous transplantation and long-term outcomes were retrieved. The expected clinical benefit of the two strategies was calculated and depicted, along with the mean costs. One-way and two-way sensitivity analyses were performed to ensure the validity of the results.

RESULTS

CT restaging plus FDG PET when residual mass is detected, results in a 2% benefit at 5yrPFS at baseline compared to FDG PET-alone restaging and remains positive for a wide range of probabilities. This strategy reduces the average cost by euro 1863 per patient, including costs of biopsy and autologous transplantation.

CONCLUSION

A more conservative approach that includes CT restaging after first-line therapy and FDG PET scan only on residual mass, is the preferred strategy in HD. Furthermore it appears to confer the maximal diagnostic yield along with a substantial reduction in the mean cost.

FDG-PET Evaluation of Response to Treatment

This article discusses evaluating response after and during therapy in various settings and for the types of cancers for which ample evidence demonstrates that PET imaging with flourodeoxyglucose provides a valuable surrogate for response to therapy. It also briefly discusses pitfalls in obtaining an optimal assessment of response and issues that need further attention for this modality to become established as an independent predictor of response to anticancer therapy.

Is [18F]fluorodeoxyglucose Positron Emission Tomography the Ultimate Tool for Response and Prognosis Assessment?

[(18)F]fluorodeoxyglucose positron emission tomography (FDG-PET) is currently the most accurate and reliable tool for the assessment of response in Hodgkin's lymphoma (HL). FDG-PET is superior to conventional imaging techniques for detection of residual disease at the end of treatment, especially in the presence of a residual mass, a frequent finding in HL. FDG-PET response assessment has also a high predictive value early after the initiation of therapy. However, whether risk-adapted treatment strategies based on FDG-PET may also improve patient outcome remains to be proved.

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.

Overview of early response assessment in lymphoma with FDG-PET

Early assessment of response to chemotherapy with fluorine-18 fluorodeoxyglucose positron emission tomography (FDG-PET) is becoming a routine part of management in patients with Hodgkin lymphoma (HL) and histologically aggressive non-Hodgkin lymphoma (NHL). Changes in FDG uptake can occur soon after the initiation of therapy and they precede changes in tumour volume. Recent studies in uniform populations of aggressive lymphomas (predominantly diffuse large B cell lymphomas) and HL have clarified the value of early response assessment with PET. These trials show that PET imaging after 2-3 chemotherapy cycles is far superior to CT-based imaging in predicting progression-free survival and can be at least as reliable as definitive response assessment at the end of therapy. This information is of great potential value to patients, but oncologists should be cautious in the use of early PET response in determining choice of therapy until some critical questions are answered. These include: When is the best time to use PET for response assessment? What is the best methodology, visual or quantitative? (For HL at least, visual reading appears superior to an SUV-based assessment). Can early responders be cured with less intensive therapy? Will survival be better for patients treated more intensively because they have a poor interim metabolic response? In the future, early PET will be crucial in developing response-adapted therapy but without further carefully designed clinical trials, oncologists will remain uncertain how best to use this new information.

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.

[Post-treatment surveillance for potentially curable malignancies]

Through an enormous research effort over the past five decades and especially due to early screening, an increasing number of cancers are potentially curable. Patients expand immeasurable energy in adhering to treatment plans and supportive care. Unfortunately, nothing prepares them for the anxiety that often comes with completion of therapy. More importantly, physicians are not properly equipped with data from controlled trials to define appropriate post-treatment surveillance, data with which they could educate patients and allay their fears. The goal of post-treatment surveillance is to enable the early detection of relapses and thus enhance the possibility of subsequent cure. Accordingly special follow-up is appropriate only for patients who can receive a second-line therapy. Clinical trials support conservative, rather than aggressive, surveillance to detect curable local relapse of breast tumors and potentially surgically curable metastases (mainly in the liver) of colon cancer. For germ-cell tumors, second-line treatments are potentially curative in nearly all instances. Follow-up for other cancers depends on patients' anxiety levels and on the costs of surveillance.

Use of FDG-PET to monitor response to chemotherapy and radiotherapy in patients with lymphomas

Lymphoma is a heterogeneous group of diseases with many curable subtypes. Primary treatment cures a significant proportion of, but not all, patients. Patients not achieving a complete remission with primary treatment, or those who relapse later, have a second chance of cure with high-dose chemotherapy and haematopoietic stem cell transplantation. Response assessment is therefore crucial in the management of lymphomas. FDG-PET has an emerging role in assessing response, both at the end of and during treatment. This article will review the current published evidence and offer some suggestions on future directions from a clinician's viewpoint.

Metabolic test with fluorine-18-fluorodeoxyglucose in staging and detection of residual tumor or recurrence in Hodgkin lymphoma

OBJECTIVE

The metabolic test using 18F-fluorodeoxyglucose is a useful tool for the management of patients with Hodgkin lymphoma, either for staging purposes or for the evaluation of suspicious masses that can frequently occur after treatment. The aim of the present study was to investigate the value of the 18F-fluorodeoxyglucose test performed with a dual-head coincident gamma camera (CGC-PET with fluorodeoxyglucose) for the staging and the detection of residual tumor of patients with Hodgkin lymphoma.

METHODS

Thirty-eight consecutive patients were included in this retrospective study; the metabolic test comprising CGC-PET with FDG was done in 18 patients for staging work-up (Group 1), and the results were compared to conventional clinical staging procedures that included computed tomography scans and bone marrow biopsy. The remaining 20 patients were evaluated with CGC-PET with fluorodeoxyglucose due to the presence of residual masses or a new lesion (Group 2).

RESULTS

The 18F-Fluorodeoxyglucose metabolic test, CGC-PET with fluorodeoxyglucose, upstaged 5 (27%) of the Group 1 patients and detected more lesions (45) than conventional methods of staging (33). Of the 20 patients in Group 2, 11 had positive18F-fluorodeoxyglucosetests, and a viable tumor was confirmed in 9 patients. Regarding the 9 patients with negative fluorodeoxyglucose metabolic tests, the 1-year probability of recurrence was 11.8%. The sensitivity, specificity, positive predictive value, negative predictive value, and accuracy of the CGC-PET with fluorodeoxyglucose test were 90%, 80%, 82%, 89%, and 85% respectively.

CONCLUSIONS

The metabolic test comprising CGC-PET with fluorodeoxyglucose had a higher diagnostic accuracy than conventional methods in the staging of Hodgkin lymphoma and thus is a valuable noninvasive tool for the diagnosis of suspicious lesions.

Routine use of PET scans after completion of therapy in pediatric Hodgkin disease results in a high false positive rate

PURPOSE

Fluoro-2-deoxy-D-glucose positron emission tomography scans are becoming standard of care in the evaluation of Hodgkin disease (HD). The frequency of false positive (FP) PET scans in pediatric HD after completion of therapy has not been well studied.

PATIENTS AND METHODS

All PET scan reports on pediatric HD patients at our institution between February 2000 and February 2005 were retrospectively reviewed. Scans were considered positive if the interpretation was most consistent with malignancy. FP results were determined by pathologic evaluation, resolution on scan, or absence of disease progression over at least 1 year without intervention.

RESULTS

We reviewed 255 PET scans on 47 patients, including 156 posttherapy scans on 34 patients. Positive predictive value for scans obtained during routine follow-up was 11%, with an FP rate of 16%. Identifiable etiologies of FP scans included: fibrosis, progressive transformation of germinal centers, abdominal wall hernia, appendicitis, thymus and HIV associated lymphadenopathy.

CONCLUSIONS

Routine PET scans after completion of therapy in pediatric HD patients have a low positive predictive value and a high FP rate. Prospective studies are needed to reduce the ambiguity of positive results. In the interim, positive PET scans after treatment should be interpreted cautiously and therapeutic decisions should not be made without histologic confirmation.

False-positive axillary lymph node on FDG-PET/CT scan resulting from immunization

An initial CT of a 59-year-old man with increasing back pain and weight loss showed lymphadenopathy in multiple nodal beds. A biopsy showed diffuse, large B-cell lymphoma (DLBCL). After initial chemotherapy, residual disease prompted an autologous stem cell transplant. After a follow-up FDG-PET/CT scan showed no FDG-avid disease, a subsequent study showed FDG uptake in a nonenlarged left axillary lymph node. Questioning elicited a recent immunization history. A follow-up PET/CT scan showed no uptake in this lymph node and no disease recurrence. Without this history, an unnecessary biopsy or treatment may have ensued. Methods to avoid such occurrences are discussed.

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.

Utility of FDG-PET/CT in follow-up of children treated for Hodgkin and non-Hodgkin lymphoma

Positron emission tomography using F-flurodeoxyglucose (FDG-PET) is considered an excellent tool for staging and monitoring disease status in adults with lymphoma. We retrospectively reviewed results of PET/CT and diagnostic computed tomography (CT) scans performed during follow-up after completion of therapy in 41 children <18 years of age with Hodgkin lymphoma and non-Hodgkin lymphoma. PET/CT scan with uptake greater than that of the liver was considered positive. Uptake that increased over the background but less than in the liver was equivocal. Clinical outcomes were obtained from medical records. Thirteen (32%) had a positive PET/CT scan and an equal number had equivocal scans in a median follow-up of 2.3 years. Diagnostic CT scans revealed new findings in 13 (32%) and persistent abnormalities in 21 (51%) of the children. Five children developed recurrent disease, and one developed a second cancer. No children with equivocal positivity developed recurrent disease. PET/CT scan was 95% sensitive, with a positive predictive value (PPV) of 53%. Diagnostic CT was 79% sensitive, with a PPV of 52%. We conclude that a negative PET/CT scan during routine follow-up for lymphoma in children strongly suggests absence of recurrence but a positive PET/CT and diagnostic CT scans have low PPV and should be interpreted with caution in this setting.

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%.