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

Exploration of the threshold SUV for diagnosis of malignancy using 18F-FBPA PET/CT

Background

The goal of the study was to evaluate the diagnostic ability of 18F-FBPA PET/CT for malignant tumors. Findings from 18F-FBPA and 18F-FDG PET/CT were compared with pathological diagnoses in patients with malignant tumors or benign lesions.

Methods

A total of 82 patients (45 males, 37 females; median age, 63 years; age range, 20–89 years) with various types of malignant tumors or benign lesions, such as inflammation and granulomas, were examined by 18F-FDG and 18F-FBPA PET/CT. Tumor uptake of FDG or FBPA was quantified using the maximum standardized uptake value (SUVmax). The final diagnosis was confirmed by cytopathology or histopathological findings of the specimen after biopsy or surgery. A ROC curve was constructed from the SUVmax values of each PET image, and the area under the curve (AUC) and cutoff values were calculated.

Results

The SUVmax for 18F-FDG PET/CT did not differ significantly for malignant tumors and benign lesions (10.9 ± 6.3 vs. 9.1 ± 2.7 P = 0.62), whereas SUVmax for 18F-FBPA PET/CT was significantly higher for malignant tumors (5.1 ± 3.0 vs. 2.9 ± 0.6, P < 0.001). The best SUVmax cutoffs for distinguishing malignant tumors from benign lesions were 11.16 for 18F-FDG PET/CT (sensitivity 0.909, specificity 0.390) and 3.24 for 18F-FBPA PET/CT (sensitivity 0.818, specificity 0.753). ROC analysis showed significantly different AUC values for 18F-FDG and 18F-FBPA PET/CT (0.547 vs. 0.834, p < 0.001).

Conclusion

18F-FBPA PET/CT showed superior diagnostic ability over 18F-FDG PET/CT in differential diagnosis of malignant tumors and benign lesions. The results of this study suggest that 18F-FBPA PET/CT diagnosis may reduce false-positive 18F-FDG PET/CT diagnoses.

Early Evaluation of Immunotherapy Response in Lymphoma Patients by 18F-FDG PET/CT: A Literature Overview

Immunotherapy is a promising therapeutic strategy both for solid and hematologic tumors, such as in Hodgkin (HL) and non-Hodgkin lymphoma (NHL). In particular, immune-checkpoint inhibitors, such as nivolumab and pembrolizumab, are increasingly used for the treatment of refractory/relapsed HL. At the same time, evidence of chimeric antigen receptor (CAR)-T-cell immunotherapy efficacy mostly in NHL is growing. In this setting, the challenge is to identify an appropriate imaging method to evaluate immunotherapy response. The role of 18F-Fluorodeoxyglucose (18F-FDG) positron-emission tomography/computed tomography (PET/CT), especially in early evaluation, is under investigation in order to guide therapeutic strategies, taking into account the possible atypical responses (hyperprogression and pseudoprogression) and immune-related adverse events that could appear on PET images. Herein, we aimed to present a critical overview about the role of 18F-FDG PET/CT in evaluating treatment response to immunotherapy in lymphoma patients.

Performance of CT Compared with 18F-FDG PET in Predicting the Efficacy of Nivolumab in Relapsed or Refractory Hodgkin Lymphoma

Background CT and fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) PET/CT performances following immune therapy are not well known in patients with relapsed or refractory Hodgkin lymphoma (RRHL). Purpose To compare CT and PET/CT for prognostic value of early response evaluation following nivolumab therapy. Materials and Methods This retrospective study included patients from 34 institutions who underwent early imaging response evaluation from July 2013 to April 2017. Three experienced readers classified imaging response by using Cheson et al and 2016 Lymphoma Response to Immunomodulatory Therapy Criteria as follows: complete (metabolic) response, partial (metabolic) response, stable disease or no metabolic response, or progressive (metabolic) disease. Primary CT and PET assessments were performed at a median of 2.0 months (interquartile range, 1.7-3.7 months) after nivolumab initiation. Kaplan-Meier analysis was used to determine the relationship of primary CT and PET assessment response categories to overall survival (OS). Agreements between primary and secondary imaging assessments were assessed by using κ analysis. Results A total of 45 patients (median age, 37 years; range, 18-77 years; 25 men) underwent a primary assessment using CT and PET/CT; 36 patients also underwent a subsequent assessment. Eleven patients (24%) died after a median follow-up of 21.2 months. CT and PET response categories were associated with OS (P = .03 for primary CT assessment; P = .02 for primary PET assessment). There was no pseudoprogression at primary CT and PET assessments. At the primary assessment, response categories by using CT were reclassified by using PET in 44% (20 of 45) of patients. Among these, 55% (11 of 20) were reclassified to complete metabolic response (complete metabolic response rate: 29% [13 of 45 patients] vs complete response rate: 4% [two of 45 patients]), with a 2-year OS probability of 100%. At the secondary assessment, complete response rate using CT increased to 17% (six of 36 patients), hence a better agreement with PET (κ = 0.78; P < .001). Conclusion Early CT and PET/CT at a median of 2 months after initiation of nivolumab predicted overall survival in relapsed or refractory Hodgkin lymphoma. Early PET detected additional patients with complete metabolic response. © RSNA, 2020 Online supplemental material is available for this article. See also the editorial by Scott and Wang in this issue.

Preliminary clinical applications of a device-dedicated whole-body positron emission tomography reconstruction method: impact on standardized uptake values

BACKGROUND

¹⁸F-fluorodeoxyglucose positron emission tomography has proven relevance in oncological diagnosis, staging and follow-up. The standardized uptake value (SUV) is one of the most widely used semi-quantitative criteria in PET imaging. However, factors such as noise and image resolution affect the measurement of the SUV. We reported earlier that a device-dedicated projector [attenuation-weighted ordered-subsets expectation maximization detector response (AW-OSEM DR), based on point-source measurements] introduces less noise than a geometrical model (AW-OSEM).

OBJECTIVE

The aim of this study was to investigate the AW-OSEM DR method's impact on SUV measurements under clinical conditions.

METHODS

We first performed a bias analysis to assess the accuracy of the quantitation for the two reconstruction methods as a function of target size and the number of iterations, with 14 acquisitions of the NEMA IEC/2001 phantom. We then used each method to calculate the maximum and average SUVs, respectively for 32 lesions.

RESULTS

For all spheres and all iterations, the bias was significantly lower with AW-OSEM DR than with AW-OSEM (P=0.012). Moreover, a paired Student's t-test showed significant intermethod differences for maximum SUV and average SUV (both P<0.001) in cancer patients. Conversely, the two methods did not differ significantly in terms of the mean SUV and signal-to-noise ratio calculated in the liver for each patient (P=0.5 and 0.08, respectively).

CONCLUSION

Phantom and patient studies were performed to quantify the effects of AW-OSEM DR on PET images. The phantom study highlighted the fact that our method produces more accurate images in terms of the SUV, which is an essential quality for ensuring correct diagnosis, follow-up and treatment planning.

F-18 FDG PET-positive fibrous dysplasia in a patient with intestinal non-Hodgkin's lymphoma

Fibrous dysplasia (FD) is a common benign bone disorder of an unclear etiology. It is known that FD can appear without an increased FDG uptake on F-18 fluorodeoxyglucose positron emission tomography/computed tomography (FDG-PET/CT). However, there are also several reports that FD showed increased FDG uptake and this mimicked malignant bone involvement on FDG-PET. Herein we describe a case of biopsy-proven FDG-PET positive FD in a patient with intestinal non-Hodgkin's lymphoma (NHL). A 45-year-old woman was diagnosed with intestinal NHL, which was removed by right hemicolectomy. After the operation, the FDG-PET/CT scan showed hypermetabolic activity in the right transverse process of the T10 vertebra. The patient then received a total of 6 cycles of R-CHOP (rituximab, cyclophosphamide, doxorubicin, vincristine, and prednisolone) chemotherapy every 3 weeks. After completion of the planned chemotherapy, the 2(nd) FDG-PET/CT showed increased FDG uptake (SUVmax=6.0 g/mL) of the previous bone lesion. The MR images revealed a T1-hypointense lesion with sharp borders in the same region, and this showed homogenous contrast enhancement on the fat-suppressed T1-weighted images. After the radiologic studies were carefully reviewed, the bone lesion was assumed to be benign such as FD. We performed bone biopsy and the histological examination confirmed the diagnosis of FD. In conclusion, bone lesions with FDG uptake need to be carefully interpreted when evaluating patients with known malignancy.

Evaluation of Musculoskeletal Disorders with PET, PET/CT, and PET/MR Imaging

18F-2-fluoro-2-deoxy-D-glucose-PET has an established role in the evaluation of hip periprosthetic infection and musculoskeletal malignancies. Determination of its role in the management of inflammatory arthritis and diabetic foot complications is ongoing. The reintroduction of fluorine F 18 sodium fluoride as a PET radiotracer may advantageously replace technetium Tc 99 m methylene diphosphonate for some non-oncologic applications, including treatment monitoring of Paget's disease andfibrous dysplasia. The combination of CT or MR imaging with PET imaging synergistically maximizes the diagnostic potential of a combined structural-functional imaging approach for the detection, characterization, and monitoring of myriad musculoskeletal disorders.