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

The Clinical Accuracy and Risk Stratification in End of Therapy 18F-FDG PET/CT in Burkitt Lymphoma

Purpose

Burkitt lymphoma (BL) is an invasive lymphoma subtype with FDG avid at ¹⁸F-FDG PET/CT, but there is currently no validated criterion in treatment evaluation and prognosis prediction. The aim of this study was to analyze the clinical accuracy of ¹⁸F-FDG PET/CT in Burkitt lymphoma in end of therapy PET/CT (EOT-PET) to assess the treatment response in BL and conduct a survival analysis with different Deauville 5-point score (DS) cutoff values.

Materials and Methods

A total of 189 patients were retrospectively included: 97 underwent baseline PET/CT and all underwent EOT-PET. Survival curves were plotted according to the Kaplan-Meier method. Different DS cutoff values in EOT-PET were evaluated for risk stratification in Burkitt lymphoma.

Results

The median progression free survival (PFS) and overall survival (OS) were 52 and 53 months, respectively. Applying the conventional DS 4 to 5, there was significant difference in outcome between EOT-PET negative and positive patients. However, the positive predictive value (PPV) (28.3% for PFS and 26.4% for OS) is low despite a high negative predictive value (NPV) (94.1% for OS and 94.9% for OS). When we moved the cutoff point to DS 5, the PPV was improved evidently (88.2% for PFS and 82.3% for OS) with the satisfactory NPV simultaneously (95.3% for PFS and 95.9% for OS).

Conclusions

EOT-PET results using DS significantly related with PFS and OS. DS of 5 may be a better cutoff point at the end of treatment to determine whether patients have a significant risk of recurrence or progress.

Overview and outcome of Hodgkin's Lymphoma: Experience of a single developing country's oncology centre

Hodgkin's Lymphoma (HL) reveals variable epidemiological and clinico-pathological features in different geographical locations. In this retrospective study, we aimed to assess the epidemiological and clinic-pathological features, and outcome of HL patients treated at one hemato-oncology centre in Erbil, northern Iraq. Medical records of 103 HL patients treated over more than six years were reviewed. Treatment outcome was evaluated by measuring the 5-year overall and progression-free survival rates. The median age of patients was 23 years, children up to 17 years constituted 31.1%, and male to female ratio was 1:1.05. The majority (96.1%) of patients presented with lymphadenopathy. Nodular sclerosis subtype was the mostly encountered histologic type (48.5%); about half of the patients (49.5%) had stage II disease. Relapse occurred in 20 patients; the 5-year overall survival for children was better (89%) compared to adult patients (79%). The associated risk features found to have adverse effects on the survival, however, only high LDH level and presence of B-symptoms at presentation showed significant correlation. The epidemiological and clinical characteristics of HL in our locality followed the pattern in the western world. The 5-year overall and progression-free survivals were far below the international rates, a matter which may necessitate a revision to HL treatment strategy at our centre.

Clinical Indications and Impact on Management: Fourth and Subsequent Posttherapy Follow-up 18F-FDG PET/CT Scans in Oncology Patients

The Centers for Medicare and Medicaid Services coverage includes 3 posttherapy ¹⁸F-FDG PET/CT scans per patient and per tumor type. Any additional follow-up ¹⁸F-FDG PET/CT scans will be reimbursed at the discretion of a local Medicare administrator, if deemed medically necessary. This study aimed to investigate common clinical indications for performing a fourth or additional follow-up ¹⁸F-FDG PET/CT scans that could affect the management of patients. Methods: This was a retrospective institutional review of 433 oncology patients (203 men; mean age, 55 y), including a total of 1,659 fourth or subsequent follow-up PET/CT scans after completion of primary treatment. Twelve indications for performing a fourth or subsequent follow-up PET/CT scan were determined, and the impact of each of the 12 indications on patients' management was evaluated. Results: The primary tumors were breast cancer (92 patients, 426 scans), non-Hodgkin lymphoma (77 patients, 208 scans), Hodgkin disease (41 patients, 182 scans), colorectal cancer (70 patients, 286 scans), melanoma (69 patients, 271 scans), and lung cancer (84 patients, 286 scans). The indications were categorized in 4 groups: PET/CT for diagnosis of tumor recurrence (303/1,659, 18.3%), PET/CT before starting therapy for tumor recurrence (64/1,659, 3.9%), PET/CT to assess therapy response for tumor recurrence (507/1,659, 30.6%), and follow-up PET/CT after completion of treatment for tumor recurrence (785/1,659, 47.3%). Overall, fourth and subsequent follow-up ¹⁸F-FDG PET/CT scans resulted in change in management in 31.6% of the scans (356 of 1,128) when the scans were obtained for medical necessities (indications 1-11), and in 5.6% of the scans (30/531) when the scans were obtained without any medical necessity (indication 12). Conclusion: The fourth and subsequent PET/CT scans obtained after completion of primary treatment led to a change in management in 31.6% of the scans when acquired for appropriate clinical reasons. Performing follow-up PET/CT without appropriate medical reason had a low impact on patients' management and should be avoided.

Three-dimensional texture analysis of contrast enhanced CT images for treatment response assessment in Hodgkin lymphoma: comparison with F-18-FDG PET

PURPOSE

To determine the diagnostic performance of three-dimensional (3D) texture analysis (TA) of contrast-enhanced computed tomography (CE-CT) images for treatment response assessment in patients with Hodgkin lymphoma (HL), compared with F-18-fludeoxyglucose (FDG) positron emission tomography/CT.

METHODS

3D TA of 48 lymph nodes in 29 patients was performed on venous-phase CE-CT images before and after chemotherapy. All lymph nodes showed pathologically elevated FDG uptake at baseline. A stepwise logistic regression with forward selection was performed to identify classic CT parameters and texture features (TF) that enable the separation of complete response (CR) and persistent disease.

RESULTS

The TF fraction of image in runs, calculated for the 45° direction, was able to correctly identify CR with an accuracy of 75%, a sensitivity of 79.3%, and a specificity of 68.4%. Classical CT features achieved an accuracy of 75%, a sensitivity of 86.2%, and a specificity of 57.9%, whereas the combination of TF and CT imaging achieved an accuracy of 83.3%, a sensitivity of 86.2%, and a specificity of 78.9%.

CONCLUSIONS

3D TA of CE-CT images is potentially useful to identify nodal residual disease in HL, with a performance comparable to that of classical CT parameters. Best results are achieved when TA and classical CT features are combined.

Role of 18F-FDG-PET/CT in the management of Burkitt lymphoma

Burkitt lymphoma (BL) is highly FDG-avid even though its usefulness in the management of these patients is still controversial.

AIM

We analyzed the role of positron emission tomography/computerized tomography (PET/CT) in staging newly diagnosed patients with BL and evaluating disease after first-line chemotherapy.

METHODS

Fifty-two PET/CTs were performed in 32 patients (20 at diagnosis, 27 after treatment, five to monitor residual disease). Involved areas were retrospectively compared with those observed in contrast-enhanced CT.

RESULTS

Discrepancies were found in 64.7% of patients for whom results of both tests at diagnosis were available (n = 17), most of them involving extranodal sites. Regarding response assessment, discrepancies were observed in 38% of patients with both tests (5/13): residual masses detected by CT with negative PET/CT. Of 27 patients with post-treatment PET/CT, 22 were in complete remission whereas one true-positive and four false-positive lesions (two nodal and two extranodal) were detected. With a median follow-up of 27 months, 22 patients with negative PET/CT did not relapse. Thus, negative predictive value (NPV) was 100%. With respect to positive predictive value (PPV), one of five patients with positive assays after treatment died due to progression while the remaining four had false-positive lesions. Nevertheless, for these four patients, mean SUVmax at nodal sites was 4.1 vs. 14.9 at diagnosis, while mean SUVmax at extranodal sites was 3.8 vs. 12.1. Thus, with a cutoff value for SUVmax < 66% of that observed at diagnosis, PPV was also 100%.

CONCLUSION

More accurate staging can be achieved using PET/CT. NPV reaches 100%, and using a ΔSUV < 66%, a high PPV is also observed.

Assessment of the prognostic capacity of pretreatment, interim, and post-therapy (18)F-FDG PET/CT in extranodal natural killer/T-cell lymphoma, nasal type

OBJECTIVE

Although the prognostic value of positron emission tomography/computed tomography (PET/CT) using [(18)F]-fluorodeoxyglucose ((18)F-FDG) has been widely confirmed for diffuse large B cell lymphoma, its value for extranodal natural killer/T-cell lymphoma, nasal type (ENKTL), is still controversial. Therefore, we designed a prospective study to investigate the prognostic value of (18)F-FDG PET/CT in patients with ENKTL.

MATERIALS AND METHODS

Thirty-three patients with newly diagnosed, untreated ENKTL, were enrolled in this study. Interim and post-therapy PET/CT scans were analyzed by visual evaluation, in accordance with the criteria set forth by the International Harmonization Project. Patients were classified as either positive or negative. Pretreatment maximum standardized uptake values (SUVmax) of (18)F-FDG were recorded in the most (18)F-FDG-intense lesions. The pretreatment (18)F-FDG SUV as well as the interim and post-therapy PET/CT results were assessed for the ability to predict progression-free survival (PFS) and overall survival (OS).

RESULTS

On the pretreatment scan, the SUVmax of the indicator lesion was >10.00 in 81.8% of patients who were treatment-resistant and ≤10.00 in 86.4% of patients who were treatment non-resistant (mean SUVmax, 12.93 and 8.10, respectively). Univariate analyses revealed that pretreatment SUVmax is a significant predictor (P < 0.01, P < 0.01) of PFS and OS, respectively. Multivariate analyses revealed that pretreatment SUVmax (P < 0.01, P = 0.01) and post-therapy PET/CT result (P < 0.01, P = 0.04) are independent predictors of PFS and OS, respectively.

CONCLUSIONS

(18)F-FDG uptakes prior to treatment and post-therapy PET/CT results can predict unfavorable outcomes following treatment in patients with ENKTL, but interim PET/CT results have little value in predicting survival.

Current status of PET/CT in the diagnosis and follow up of lymphomas

Lymphomas are a heterogeneous group of malignancies that have a distinct biological behavior according to the subtype and degree of differentiation. Adequate staging, which has a direct impact on prognosis, is essential to properly plan therapy. Structural cross-sectional imaging, such as computed tomography, has been the standard imaging tool to stage and monitor patients with lymphoma. However, molecular imaging such as positron emission tomography has shown complementary diagnostic and prognostic values. This review discusses the current value of positron emission tomography imaging using 2-[fluorine-18]fluoro-2-deoxy-d-glucose in staging, restaging, monitoring and detecting relapse in Hodgkin's and non-Hodgkin lymphoma.

[Quantitative and qualitative evaluation of the interim PET/CT in lymphoma treatment in the prediction of complete metabolic response]

OBJECTIVE

To compare two different methods for the interpretation of interim PET/CT (PET/CT-i) in lymphomas, and to establish which one best predicts a complete metabolic response (CMR) in the PET/CT study at the end of treatment (PET/CT-et).

MATERIAL AND METHODS

Retrospective longitudinal analysis of the PET/CT studies for staging (PET/CT-s), PET/CT-i and PET/CT-et of 65 patients, 35 Hodgkin's lymphoma (HL) and 30 Non-HL. The PET/CT-i was performed between the second and fourth chemotherapy cycle. It was interpreted using two different criteria: qualitative criteria (5 point visual scale), semiquantitative criteria (percentage difference between the lesion with more SUVmax in the PET/CT-s and PET/CT-i). We analyzed the likelihood of obtaining a CMR in the PET/CT-et according to the results obtained on the PET/CT-i with these two criteria.

RESULTS

We obtained sensitivity (S), specificity (Sp), positive predictive values (PPV), negative predictive values (NPV) and likelihood ratio (LR) for the qualitative/semiquantitative method of 91%/80%, 76.2%/67%, 88.9%/83.3%, 80%/60.9% and 32%/7.8%, respectively, to predict a CMR in the PET/CT-et. There were no statistically significant differences between the LR of both methods (p=0.1942).

CONCLUSION

We found clear differences in S, Sp, PPV and NPV between both interpretation criteria for the PET/CT-i to predict a CMR in the PET/CT-et. Nevertheless, we cannot confirm the superiority of the qualitative method over the semiqualitative method for this purpose as no statistically significance differences were found in their LR in our study.

Impact of FDG-PET/CT in the management of lymphoma

Since the introduction of (67)Gallium-citrate 30 years ago, nuclear medicine has played an important role in the evaluation of malignant lymphoma. During that time, several radiotracers were evaluated as potential alternatives for the diagnosis of lymphoma, but the introduction of (18)F-fluorodeoxyglucose PET (FDG-PET) marked a major turning point. FDG-PET took over most of the role of gallium, and is now an essential tool in the diagnosis of lymphoma. FDG-PET is increasingly being used for assessment of the tumor staging prior to treatment, for evaluating the response to treatment, and for monitoring the early reactions to therapy to predict the final outcome. FDG-PET has been shown to have more accurate diagnostic capability than conventional CT and MRI for distinguishing the tumor necrosis and residual masses frequently seen after therapy in lymphoma patients without any clinical and biochemical manifestation. Malignant lymphoma is the first disease for which FDG-PET was adopted as a tool for response assessment in the international standard criteria. However, lymphoma does not always display a clear high uptake, and there are some pitfalls in assessing the response to therapy. This review will highlight the most important applications of FDG-PET in lymphoma, focusing on the advantages and pitfalls of this imaging, and past and ongoing efforts to standardize the use of FDG-PET, particularly in response to assessment and therapy monitoring.

18F-FDG PET after 2 cycles of ABVD predicts event-free survival in early and advanced Hodgkin lymphoma

Our objective was to assess the prognostic value of (18)F-FDG PET after 2 cycles of chemotherapy using doxorubicin, bleomycin, vinblastine, and dacarbazine (ABVD) in Hodgkin lymphoma (HL) patients overall and in subgroups of patients with early and advanced stages and with low and high risks according to the International Prognostic Score (IPS).

METHODS

One hundred fifteen patients with newly diagnosed HL were prospectively included in the study. All underwent standard ABVD therapy followed by consolidation radiotherapy in cases of bulky disease. After 2 cycles of ABVD, the patients were evaluated with PET (PET2). Prognostic analysis compared the 3-y event-free survival (EFS) rate to the PET2 results, clinical data, and IPS.

RESULTS

Of the 104 evaluated patients, 93 achieved complete remission after first-line therapy. During a median follow-up of 36 mo, relapse or disease progression was seen in 22 patients. Treatment failure was seen in 16 of the 30 PET2-positive patients and in only 6 of the 74 PET2-negative patients. PET2 was the only significant prognostic factor. The 3-y EFS was 53.4% for PET2-positive patients and 90.5% for PET2-negative ones (P < 0.001). When patients were categorized according to low or high IPS risk and according to early or advanced stage of disease, PET2 was also significantly associated with treatment outcome.

CONCLUSION

PET2 is an accurate and independent predictor of EFS in HL. A negative interim (18)F-FDG PET result is highly predictive of treatment success in overall HL patients, as well as in subgroups with early or advanced-stage disease and with low or high IPS risk.

False-positive F-18 FDG uptake in PET/CT studies in pediatric patients with abdominal Burkitt's lymphoma

INTRODUCTION

In pediatric patients with abdominal Burkitt's lymphoma, the involvement of the gastrointestinal tract and abdominal lymph nodes are the main presenting feature of the disease. Chemotherapy is the main treatment modality and could be preceded by surgical excision of the abdominal masses. To achieve cure or long-term disease-free survival a balance has to be struck between aggressive chemotherapy and the probability of tumor necrosis secondary to treatment complicated by acute infections, perforation or intestinal bleeding. F-18 fluorodeoxyglucose-positron emission tomography/computed tomography (F-18 FDG-PET/CT) has been recommended over conventional imaging modalities for the follow-up of these patients and for monitoring treatment response. As the incidences of postchemotherapy complications are high, the positive predictive value of PET/CT studies in these patients is very low and the false-positive rate is high from acute infections and tumor necrosis. Accordingly, histopathological confirmation of positive lesions on F-18 FDG-PET/CT studies is essential. This is especially important as post-therapy complications might present with nonspecific and nonurgent symptoms. At the same time initiating a second course of salvage chemotherapy is risky.

AIM OF STUDY

Retrospectively reviewed F-18 FDG-PET/CT studies for 28 pediatric patients with abdominal Burkitt's lymphoma and diffuse large B-cell lymphoma after their treatment with chemotherapy or surgery.

RESULTS

Four positive studies were found. All had pathological verification and were because of acute inflammation and tumor necrosis and there was no evidence of viable tumor cells. One patient had multiple recurrent lesions in the abdomen after the initial surgical excision and before starting chemotherapy. The incidence of acute complications in this series is 10.7%.

CONCLUSION

This study confirms the high incidence of tumor necrosis and inflammation after chemotherapy for the abdominal Burkitt's lymphoma and consequently, the incidence of true-positive F-18 FDG studies is low. This necessitates the need for histopathological confirmation of positive studies.

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.

PET scanning and prognosis in Hodgkin's lymphoma

PURPOSE OF REVIEW

Risk-adapted treatment strategies are currently under investigation in the management of patients with lymphoma. This review presents the latest evidence for the use of early interim [(18)F]-fluorodeoxyglucose-positron emission tomography for risk-adapted treatment in Hodgkin's lymphoma.

RECENT FINDINGS

In recent years, PET after two cycles of ABVD (adriamycin, bleomycin, vincristin, and dexamethasone) was shown to be the only independent prognostic factor for the prediction of relapse in Hodgkin's lymphoma and to have at least the same prognostic accuracy as end-of-treatment PET. A high prognostic value of PET was reported even earlier, before the second cycle of chemotherapy. The earlier PET becomes negative, the more chemosensitive the disease, which may offer opportunities toward the limitation of the therapy. However, more false-positive lesions occur at earlier time points, and preliminary results indicate that accuracy of PET results differs after BEACOPP (bleomycin, etoposide, doxorubicin, cyclophosphamide, vincristine, procarbazine, and prednisone) and immunotherapy.

SUMMARY

[(18)F]-Fluorodeoxyglucose-positron emission tomography after two cycles of ABVD is now recognized as the single most important factor in defining disease-specific outcome and is highly promising for investigation of response-adapted treatment strategies. It is now recognized that the optimal time point of PET for response evaluation is crucial and dependent on the administered treatment. Standardization of PET-response is essential and should be adapted to time-dependent and therapy-dependent changes.

The rationale and role of radiation therapy in the treatment of patients with diffuse large B-cell lymphoma in the Rituximab era

Developments in the evaluation and systemic management of diffuse large B-cell lymphoma (DLBCL) require ongoing assessment of the role of external beam radiotherapy in management. This review assesses data regarding the use of radiotherapy in the initial management of early stage and advanced DLBCL, and considers the implications of bulky and residual disease, and the contribution of PET scanning, to decisions regarding the use of radiotherapy after chemotherapy. Limited R-CHOP plus radiotherapy, or full dose R-CHOP alone, are both likely to cure approximately 90% of patients with low risk early stage disease. The choice of therapy will depend on considerations of acute and late toxicity of the two approaches, taking into account individual patient risk profiles and preferences. Unfavorable early-stage and advanced-stage disease require treatment with full dose R-CHOP. The presence of bulky disease predicts for a higher risk of relapse, which may be partly ameliorated by the addition of radiotherapy. The rapidity of response on PET scanning, the presence of a posttherapy residual mass, the potential toxicity of radiotherapy and the available salvage options all need to be considered on a patient by patient basis, when considering the use of radiotherapy for advanced disease.

Predictive and prognostic value of FDG-PET

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