Are 18fluorodeoxyglucose positron emission tomography and magnetic resonance imaging useful in the prediction of relapse in lymphoma residual masses?

FDG-PET is Superior to Gallium Scintigraphy in Staging and More Sensitive in the Follow-up of Patients withde novoHodgkin Lymphoma: A Blinded Comparison

Accurate staging of Hodgkin lymphoma (HD) allows for minimization of therapy and reduction of long-term toxicities. The present study prospectively compares FDG-PET with gallium/SPECT scintigraphy at time of diagnosis and in follow-up of 36 patients with HD. Prior to therapy, whole body FDG-PET and gallium/SPECT were performed. Follow-up scans were obtained after 3 cycles of chemotherapy (n = 22), and at the end of chemotherapy (n = 32). Two nuclear medicine physicians independently interpreted scans in blinded and random order and a consensus was obtained. Baseline scans revealed a greater number of supradiaphragmatic disease sites detected by PET, and 5 patients had splenic involvement on PET not noted by gallium (P = 0.05); 3 patients were upstaged on PET. Midway through therapy, 5 patients had positive PET (4 of whom relapsed), and 3 had positive gallium (1 relapsed). At conclusion of chemotherapy, 8 patients had a positive PET (4 relapsed) and 3 had a positive gallium (2 relapsed). In conclusion, diagnostic PET and gallium are largely concordant, with the exception of unique detection of splenic disease by PET. However, more patients have persistently positive PET at the end of chemotherapy compared with gallium (P = 0.04), although only half of these patients have relapsed.

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.

Comparison of gallium and PET scans at diagnosis and follow-up of pediatric patients with Hodgkin lymphoma

BACKGROUND

Positron emission tomography (PET) and gallium scans facilitate diagnosis and staging, evaluation of response to therapy, and monitoring for relapse in Hodgkin lymphoma (HL), but have not been compared in pediatric HL.

PROCEDURE

We performed concurrent PET and gallium scans on 44 pediatric HL patients at diagnosis, early response, off chemotherapy, and off-therapy evaluations. PET and gallium scans were compared to each other and to computed tomography (CT) alone to determine whether either modality led to a change in stage or modified the results of the early response evaluation, which was used to determine the radiation dose.

RESULTS

PET upstaged four patients at diagnosis (2 from stage I to II, one II to III, and one III to IV), but did not lead to a change in therapy in any of them. It changed response category in two patients at early response evaluation, leading to a change in radiation dose for 1 patient (25.5 Gy instead of 15 Gy to the spleen). Gallium did not change the stage of treatment for any patient. The negative predictive values for eventual lymphoma relapse of PET and gallium scans at off therapy were 89% and 83%, respectively; the positive predictive value of PET at off therapy is 29%.

CONCLUSION

PET appears to be superior to gallium in pediatric HL; future studies will determine the optimal timing of PET to assess early response and the utility of quantitative interpretation of the avidity of specific nodal sites.

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.

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.

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.

Survival after relapse in children with solid tumors: a follow-up study from the Italian off-therapy registry

BACKGROUND

Despite the increased survival of children with solid tumors, a significant proportion of cases still relapse following treatment discontinuation, and knowledge about the long-term outcome of this selected group of patients remains incomplete.

OBJECTIVE

To describe the long-term outcome of children treated for a solid tumor who relapsed after the elective end of therapy, and to explore factors associated with survival.

METHODS

All patients with the selected diagnoses-Hodgkin disease (HD), neuroblastoma (NB), tumor of the central nervous system (CNS), Wilms tumor (WT), or soft tissue sarcoma (STS)-enrolled in the Italian Pediatric Off-Therapy Registry in the period 1980-1998 were evaluated. Out of 3,927 patients, 694 had relapsed after treatment suspension; 639 were available for analysis. Survival and event-free survival were estimated by the Kaplan-Meier method. The log-rank test was used to assess differences in survival among the various types of cancer considered. Multivariate Cox proportional hazards analysis was adopted to explore possible prognostic factors.

RESULTS

There were 335 deaths: most of them (93%) were related to the primary cancer. The overall survival rate after relapse was 38% (95% CI 33-42) at 5 years, and 32% (95% CI 27-36%) at 15 years, while event free survival was 31% (95% CI 26-35) and 26% (95% CI 22-30%), respectively. There were significant differences according to the original diagnosis, with patients with HD doing better, and those with NB, CNS, and STS worse. No improvement of prognosis was evident over time. Post-relapse stem cell transplantation was associated with decreased risk of death only in the first year, not thereafter.

CONCLUSIONS

Overall, patients with solid tumors who relapse after treatment discontinuation have a poor outcome, but significant differences exist according to the tumor types.

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%.

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

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

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.

The role of PET imaging in lymphoma

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

FDG-PET/CT in re-staging of patients with lymphoma

The aim of this study was to evaluate the clinical significance of combined fluorine-18 fluorodeoxyglucose positron emission tomography and computed tomography (FDG-PET/CT) in patients with lymphoma, and to compare the FDG-PET/CT staging results with those of FDG-PET and CT alone. Twenty-seven patients were studied. Each patient had clinical follow-up for >12 months and entered complete follow-up evaluation. Patient-based evaluation showed a sensitivity of 78% for CT alone, 86% for FDG-PET alone, 93% for CT and FDG-PET read side by side, and 93% for combined FDG-PET/CT imaging. Region-based evaluation showed a sensitivity for regional lymph node involvement of 61%, 78%, 91% and 96% respectively. FDG-PET/CT imaging is superior to CT alone ( P=0.02) and has additional benefit over FDG-PET alone due to exact anatomical localisation. We conclude that FDG-PET/CT imaging is accurate in re-staging lymphoma and offers advantages over separate FDG-PET and CT imaging.

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.

Positron emission tomography with [(18)F]FDG for therapy response monitoring in lymphoma patients

Lymphomas are a heterogeneous group of diseases with differing histopathology, clinical behaviour, response to therapy and outcome. Lymphomas are highly sensitive to chemotherapy and radiotherapy, and the recent developments in treatment have considerably improved clinical outcome. However, there is increasing recognition that this has been at the cost of long-term treatment-related effects in a relatively young patient population. Thus, one of the most challenging aspects in the imaging of lymphoma patients is tailoring the intensity of the treatment to the individual patient. This paper reviews recently published data concerning the use of fluorine-18 fluorodeoxyglucose positron emission tomography ([(18)F]FDG-PET) for therapy monitoring in lymphoma patients and highlights the shortcomings and future directions. A temporary strategy for the implementation of [(18)F]FDG-PET in the management of lymphoma patients is proposed.

PET and restaging of malignant lymphoma including residual masses and relapse

Differentiation of post-therapeutic scar tissue from active lymphoma is unsatisfactory when using only morphological imaging approaches. Positron emission tomography (PET) with fluorine-18 fluorodeoxyglucose (FDG) may provide superior clinical information by enabling biochemical tissue characterisation, with enhanced FDG uptake in viable post-therapeutic lymphoma masses and very low uptake in indolent fibrotic tissue. With this in mind, 15 recently published studies reporting the results of differentiation of viable lymphoma from scar tissue in 723 patients were analysed. Sensitivity of FDG-PET for detection of active disease was 71-100%, and the specificity was 69-100%. Accordingly, FDG-PET had a high negative predictive value of 80-100%. In contrast, the specificity and positive predictive value (PPV) of computed tomography were low (4-31% and 19-60%, respectively, except in one study in which the PPV was 82%). Residual masses that were positive on PET were associated with a progression-free survival of 0-40%. Although not perfect, the biochemical approach for characterisation of residual masses in lymphoma with FDG-PET at present seems the most accurate way to differentiate scar tissue from viable residual lymphoma.

Assessment of response to therapy using conventional imaging

The response of lymphoma to treatment is usually documented using cross-sectional imaging. The definitions of response and the changes seen on CT and MRI in the chest and abdomen are well recognised. However, the appearances of residual masses are more variable and features that may help in diagnosis will be included in this review.

PET in lymphoma: what are the oncologist's needs?

Fluorine-18 fluorodeoxyglucose positron emission tomography (PET) has a number of potential advantages for the oncologist in refining and improving the management of lymphomas. Currently the most promising appear to be in the early prediction of response to chemotherapy, evaluation of the residual mass and improved radiotherapy planning. Other important areas which require assessment are its value in refining prognostic indices at staging and its role in follow-up. The added value of the new combined PET-CT scanners requires careful evaluation in each of these settings, where combined morphological and functional information may provide optimal disease assessment. The ultimate aim is to improve the management of patients with lymphoma by identifying those patients who can be cured with minimal treatment and equally those for whom conventional treatment is doomed to failure and in whom more intensive strategies should be employed from the outset.

Positron emission tomography with [18F]2-fluoro-D-2-deoxyglucose (FDG-PET) predicts relapse of malignant lymphoma after high-dose therapy with stem cell transplantation

We have determined the predictive value of [18F]2-fluoro-2-deoxy-glucose (FDG-PET) in patients with Hodgkin's disease (HD) and aggressive non-Hodgkin's lymphoma (NHL) scheduled for high-dose therapy with stem cell transplantation (HDT/SCT). Inclusion criteria were the presence of an FDG-PET scan after chemotherapy (ChT) within 8 weeks prior to HDT/SCT and available follow-up data. Sixteen patients (10 NHL and six HD) were observed during a follow-up period of 4 to 28 months (median 13 months). Before SCT, five patients had a negative PET, three were weakly positive, two moderately positive, and six strongly positive. None of the five patients with a negative PET before HDT/SCT relapsed and two of three patients with a weakly positive scan are still in remission after HDT/SCT. Of eight patients with a moderate or high positive PET before HDT/SCT, seven relapsed and one died of early HDT/SCT related complications (P< 0.01). Three of eight relapsing patients died of lymphoma 5 to 10 months after SCT and in one additional patient not responding to HDT/SCT, the main cause of death was chronic toxicity 4 months after transplantation. After 12 months, in PET-negative patients the overall and relapse-free survival was 100%, in PET-positive patients 55% and 18%, respectively. In NHL, two patients with negative PET, but with an age-adjusted international prognostic index (AaIPI) of 2 and one with AaIPI = 1 are still in remission. In the seven PET-positive subjects, one patient with AaIPI = 0, three with AaIPI = 1, and two with AaIPI = 2 relapsed. We conclude that FDG-PET is accurate in the prediction of relapse prior to HDT/SCT in patients with lymphoma. It provides additional information when compared with the AaIPI.

Prognostic value of positron emission tomography in the evaluation of post-treatment residual mass in patients with Hodgkin's disease and non-Hodgkin's lymphoma

The prognostic value of 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) in the assessment of post-treatment residual masses in patients with Hodgkin's disease (HD) or non-Hodgkin's lymphomas (NHL) was evaluated. We prospectively studied 58 patients with HD (n = 43) or NHL (n = 15) who had post-therapeutic complete remission with residual masses (CRu) indicated by computerized tomography. Analysis of 62 residual locations by FDG-PET was performed separately for HD and NHL. Patients with a PET-positive residual mass [standardized uptake value (SUV) > 3] had a recurrence rate of 62.5% (5/8 patients), whereas patients with PET-negative residual mass (SUV < or =3.0) showed a recurrence rate of 4% (2/50 patients, P = 0.004). A positive FDG-PET study correlated with a significantly poorer progression-free survival (P < 0.00001). No recurrence occurred in any of the 39 HD patients with a negative PET scan (negative predictive value, 100%). Four out of four NHL patients with a positive PET study relapsed (positive predictive value, 100%). In conclusion, FDG-PET is a suitable non-invasive method with a high degree of accuracy in the prediction of early recurrence in lymphoma patients with CRu.

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.