Positron emission tomography (PET) with 18F-fluorodeoxyglucose (18F-FDG) for the staging of low-grade non-Hodgkin's lymphoma (NHL)

Applications of 18F-Fluorodesoxyglucose PET Imaging in Leukemia

The main finding that 18F-FDG PET imaging can reveal in patients with leukemias is the presence of bone marrow (BM) infiltration in both acute or chronic forms. This ability can influence and guide the use of BM biopsy but also assess to therapy response. Additionally 18F-FDG PET imaging has been reported as particularly useful for the diagnosis of leukemias in patients with non specific symptoms. In the case of acute leukemias it revealed also a role for the evaluation of extramedullary forms while in the case of chronic forms a role for the assessment of Richter transformation has been reported.

PET radiotracers and fluorescent probes for imaging human carbonic anhydrase IX and XII in hypoxic tumors

Positron emission tomography (PET) and fluorescent imaging play a pivotal role in medical diagnosis, biomedical oncologic research, and drug development process, which include identification of target location, target engagement, but also prove on mechanism of action or pharmacokinetics of new drug candidates. PET estimates physiological changes at the molecular level using specific radiotracers containing a short-lived positron emitting radionuclide such as fluorine-18 or carbon-11, whereas fluorescent imaging techniques use fluorescent probes labeled with suitable drug candidates for detection at the molecular level. The human carbonic anhydrase (hCA) isoforms IX and XII are overexpressed in hypoxic cancer cells, promoting tumor growth by regulating extra/intracellular pH, ferroptosis, and metabolism, being recognized as promising targets for anticancer theranostic agents. In this review, we have focused on PET radiotracers as well as fluorescent probes for diagnosis and treatment of tumors expressing hCA IX and hCA XII.

Lipid uptake in chronic lymphocytic leukemia

Many cancers rely on glucose as an energy source, but it is becoming increasingly apparent that some cancers use alternate substrates to fuel their proliferation. Chronic lymphocytic leukaemia (CLL) is one such cancer. Through the use of flow cytometry and confocal microscopy, low levels of glucose uptake were observed in the OSU-CLL and HG3 CLL cell lines relative to highly glucose-avid Raji cells (Burkitt's lymphoma). Glucose uptake in CLL cells correlated with low expression of the GLUT1 and GLUT3 receptors. In contrast, both CLL cell lines and primary CLL cells, but not healthy B cells, were found to rapidly internalise medium- and long-chain, but not short-chain, fatty acids (FAs). Differential FA uptake was also observed in primary cells taken from patients with unmutated immunoglobulin heavy variable chain usage (IGHV) compared with patients with mutated IGHV. Delipidation of serum in the culture medium slowed the proliferation and significantly reduced the viability of OSU-CLL and HG3 cells, effects that were partially reversed by supplementation with a chemically defined lipid concentrate. These observations highlight the potential importance of FAs in the pathogenesis of CLL and raise the possibility that targeting FA utilisation may represent a novel therapeutic and prognostic approach in this disease.

The Importance of Cellular Metabolic Pathways in Pathogenesis and Selective Treatments of Hematological Malignancies

Despite recent advancements in the treatment of hematologic malignancies and the emergence of newer and more sophisticated therapeutic approaches such as immunotherapy, long-term overall survival remains unsatisfactory. Metabolic alteration, as an important hallmark of cancer cells, not only contributes to the malignant transformation of cells, but also promotes tumor progression and metastasis. As an immune-escape mechanism, the metabolic adaptation of the bone marrow microenvironment and leukemic cells is a major player in the suppression of anti-leukemia immune responses. Therefore, metabolic rewiring in leukemia would provide promising opportunities for newer therapeutic interventions. Several therapeutic agents which affect essential bioenergetic pathways in cancer cells including glycolysis, β-oxidation of fatty acids and Krebs cycle, or anabolic pathways such as lipid biosynthesis and pentose phosphate pathway, are being tested in various types of cancers. So far, numerous preclinical or clinical trial studies using such metabolic agents alone or in combination with other remedies such as immunotherapy are in progress and have demonstrated promising outcomes. In this review, we aim to argue the importance of metabolic alterations and bioenergetic pathways in different types of leukemia and their vital roles in disease development. Designing treatments based on targeting leukemic cells vulnerabilities, particularly in nonresponsive leukemia patients, should be warranted.

Limited benefit of additional contrast-enhanced CT to end-of-treatment PET/CT evaluation in patients with follicular lymphoma

Despite follicular lymphoma (FL) is frequently characterized by a moderate increase of glucose metabolism, PET/CT examinations provides valuable information for staging and response assessment of the disease. The aim of the study was to assess and compare the diagnostic performance of PET/ldCT and PET/ceCT, respectively, in evaluating FL patients at the end of treatment. Fifty FL consecutive patients who underwent end-of-therapy PET/CT with both ldCT and ceCT were analyzed. Two blinded observers independently assessed PET/ldCT and PET/ceCT applying the Deauville score (DS) and Lugano classification criteria. PET imaging obtained after the end-of-treatment (EoT) was classified as showing PET and ce-CT matched response (concordant imaging group, CIG) or PET and ce-CT unmatched response (discordant imaging group, DIG). Relapse rate and Event-Free Survival (EFS) were compared between CIG and DIG patients. Overall, no differences in metabolic response classification were observed between PET/ldCT and PET/ceCT. In 13 (26%) patients PET/ceCT identified additional FDG-negative nodal lesions in mesenteric, retroperitoneal and iliac regions. However, in all cases, final DS remained unchanged and the additional results did not modify the following therapeutic decision. Among patients, who obtained complete metabolic response a comparable rate of relapse was registered in DIG 3/13 (23%) and CIG subgroups 5/20 (25%) [p = 0.899]. In all 3 DIG cohort patients who relapsed the recurrent disease involved also, but not exclusively, PET negative lymph nodes detected by ceCT. In overall population metabolic response defined by PET/ldCT predicted EFS [76% (group of patients with metabolic response) vs 35% (group of patients with residual disease), p = 0.0013] significantly better than ceCT-Based response assessment [75% (group of patients with complete response) vs 53% (group of patients with residual disease), p = 0.06]. Our study demonstrates a negligible diagnostic and predictive value of ceCT performed in addition to standard ¹⁸FDG PET/ldCT for EoT response evaluation in FLs. PET/ldCT should be performed as first-line imaging procedure, also in patients with prevalent abdominal and pelvic involvement, limiting the acquisition of ceCT in selected cases. This tailored approach would contribute to avoid useless radiation exposure and preserve renal function of patients.

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

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

Hybrid imaging of the abdomen and pelvis

Accurate imaging is crucial for lesion detection in abdominal organs, for the noninvasive characterization of focal and diffuse abnormalities, and for surgical planning. To accomplish these tasks, several imaging modalities such as multidetector computer tomography (MDCT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) are used for abdominal imaging, providing important morphological, functional or metabolic information. More recently, PET/MRI has been gaining attention due to the possibility of combining high-resolution imaging with metabolic imaging. PET/MRI is a novel hybrid imaging technology that in the near future might play a pivotal role in the clinical management of oncologic and inflammatory abdominopelvic diseases. Despite the still limited number of published clinical studies, PET/MRI has been proven to be at least equivalent to PET/CT and to standalone MRI in a variety of oncologic disease. Moreover, in selected and focused clinical studies, it has been proven to outperform current standard of care imaging, for example, in evaluating cholangiocarcinomas, liver metastases, untreated and treated rectal cancer. This has also had an impact on therapeuticmanagement in some studies. Therefore in some institutions, including those of the authors, PET/MRI is becoming the new standard imaging modality in staging treatment-naïve intrahepatic massforming cholangiocarcinomas and prior to complicated hepatic surgery.

Comparison of Bone Marrow Involvement with Bone Marrow Biopsy and PET-CT and Evaluation of Any Effects on Survival in Patients Diagnosed with Hodgkin and Non-Hodgkin Lymphoma

We aimed to demonstrate whether PET-CT can replace bone marrow biopsy in detecting bone marrow involvement in subtypes of lymphoma. In addition, we aimed to also reveal whether there is a difference between the mean survival of patients with bone marrow involvement via PET-CT or biopsy. A total of 276 newly diagnosed lymphoma patients who underwent bone marrow biopsy and PET-CT prior to the treatment were scanned retrospectively. Bone marrow biopsy was used as the standard method to investigate the presence of bone marrow involvement in PET-CT. The relationship between bone marrow involvement and mean survival was compared using both methods. Out of the 276 patients, bone marrow involvement was detected with PET-CT and with biopsy, respectively in 56 patients (20.2%) and in 78 patients (28.2%). In terms of PET-CT's accuracy with respect to revealing bone marrow involvement, the highest rates were achieved respectively in diffuse large B cell lymphoma (DLBCL) (87.4%) and Hodgkin lymphoma (HL) (77.7%). In both the PET-CT and bone marrow biopsy methods, Overall Survival (OS) was found to be significantly shorter in patients with involvement than in patients without involvement (P: 0.001). PET-CT may replace bone marrow (BM) biopsy in detecting the bone marrow involvement in aggressive lymphoma subtypes such as DLBCL and HL. The presence of BM involvement at the time of diagnosis in both PET-CT and BM biopsy is associated with poor prognosis, and OS is short in this group.

Applications of PET in Diagnosis and Prognosis of Leukemia

As a malignant hematopoietic stem cell disease, leukemia remains life-threatening due to its increasing incidence rate and mortality rate. Therefore, its early diagnosis and treatment play a very important role. In the present work, we systematically reviewed the current applications and future directions of positron emission tomography (PET) in patients with leukemia, especially ¹⁸F-FDG PET/CT. As a useful imaging approach, PET significantly contributes to the diagnosis and treatment of different types of leukemia, especially in the evaluation of extramedullary infiltration, monitoring of leukemia relapse, detection of Richter’s transformation (RT), and assessment of the inflammatory activity associated with acute graft versus host disease. Future investigations should be focused on the potential of PET/CT in the prediction of clinical outcomes in patients with leukemia and the utility of novel radiotracers.

[Hybrid imaging of the abdomen and pelvis. German version]

Accurate imaging is crucial for lesion detection in abdominal organs, for the noninvasive characterization of focal and diffuse abnormalities, and for surgical planning. To accomplish these tasks, several imaging modalities such as multidetector computer tomography (MDCT), magnetic resonance imaging (MRI) and positron emission tomography/computed tomography (PET/CT) are used for abdominal imaging, providing important morphological, functional or metabolic information. More recently, PET/MRI has been gaining attention due to the possibility of combining high-resolution imaging with metabolic imaging. PET/MRI is a novel hybrid imaging technology that in the near future might play a pivotal role in the clinical management of oncologic and inflammatory abdominopelvic diseases. Despite the still limited number of published clinical studies, PET/MRI has been proven to be at least equivalent to PET/CT and to stand-alone MRI in a variety of oncologic disease. Moreover, in selected and focused clinical studies, it has been proven to outperform current standard of care imaging, for example, in evaluating cholangiocarcinomas, liver metastases, untreated and treated rectal cancer. This has also had an impact on therapeutic management in some studies. Therefore in some institutions, including those of the authors, PET/MRI is becoming the new standard imaging modality in staging treatment-naïve intrahepatic mass-forming cholangiocarcinomas and prior to complicated hepatic surgery.

PET/CT in Disease Detection and Follow-up of Subcutaneous Involvement in Marginal Zone Lymphoma

BACKGROUND

The value of positron emission tomography/computed tomography (PET/CT) in the staging and assessment of treatment response in marginal zone lymphoma (MZL) lymphomas remains controversial. We investigated radiologic characteristics of subcutaneous MZL as imaged on PET/CT scans.

PATIENTS AND METHODS

From the records of a single medical center, for the years 2008 and 2017, we identified subcutaneous lesions in PET/CT scans of patients with histopathologically confirmed MZL in sites other than subcutaneous tissue.

RESULTS

Of 571 scans of 178 patients, subcutaneous lesions were found in 20 (11%). Lesions were located in soft tissue structures, mainly along the lateral aspects of the buttocks, thighs and lower and upper back areas, the flank, and the shoulders. Median lengths of the long and short axes of the lesions were 2.0 (range, 1.1-6.0) cm and 0.8 (range, 0.3-2.0) cm, respectively. Median standardized maximum uptake value was 2.3 (range, 0.9-7.6). In 12 patients (60%), MZL was diagnosed at an early stage; 15 (75%) had lymph node involvement and 10 (50%) extranodal involvement. One had spleen and 2 had cutaneous involvement; none had gastric findings.

CONCLUSION

The findings of this study support the usefulness of PET/CT in the detection of subcutaneous MZL as well as in staging and treatment decisions.

Biological Features and Prognostic Impact of Bone Marrow Infiltration in Patients with Diffuse Large B-Cell Lymphoma

The biology and clinical impact of bone marrow (BM) infiltration in patients with diffuse large B-cell lymphoma (DLBCL) remains unclear in the rituximab era. We retrospectively analyzed 232 patients diagnosed with DLBCL at our center between 1999 and 2014. Concordant-presence of large cells similar to those of the lymph node biopsy- and discordant-infiltration by small cells forming lymphoid aggregates, lacking cytological atypia-BM infiltration was defined by histological criteria and further characterized by flow cytometry (FCM). Cell of origin (COO) was determined using Hans’ algorithm. For the clonal relationship between tumor and discordant BM, the VDJH rearrangement was analyzed. Survival analyses were restricted to 189 patients treated with rituximab and chemotherapy. Thirty-six (16%) had concordant, and 37 (16%) discordant BM infiltration. FCM described different indolent lymphomas among discordant cases, clonally related with DLBCL in 10/13 available samples. Median follow-up was 58 months. 5-year-progression-free survival (PFS) for non-infiltrated, discordant and concordant groups was 68%, 65% and 30%, respectively (p < 0.001). Combining COO and BM infiltration, patients with discordant BM and non-germinal center B-cell COO also had decreased 5-year-PFS (41.9%). In multivariate analysis, concordant BM had an independent effect on PFS (HR 2.5, p = 0.01). Five-year cumulative incidence of central nervous system (CNS) relapse was 21%, 4% and 1% in concordant, discordant and non-infiltrated groups, respectively (p < 0.001). In conclusion, concordant BM infiltration represents a subset with poor prognosis, whereas the prognostic impact of discordant BM infiltration could be limited to non-CGB cases.

Correlations between maximum standardized uptake value measured via 18F-fluorodeoxyglucose positron emission tomography/computed tomography and clinical variables and biochemical indicators in adult lymphoma

Objectives

The aim of the current study was to investigate whether the maximum standardized uptake value (SUVmax) measured by ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography (PET)/computed tomography (CT) could discriminate between aggressive and indolent non-Hodgkin lymphomas (NHLs) and correlations between the SUVmax and clinical variables and serum biochemical indicators in adult lymphoma.

Methods

A total of 103 patients with lymphoma confirmed by biopsy, pretreatment ¹⁸F-FDG PET/CT scans, and a complete medical record were retrospectively enrolled in the study. Clinical variables that were evaluated included stage, pathological subtype, International Prognostic Index (IPI) score, and Ki-67 index, as well as serum biochemical indicators (e.g., lactate dehydrogenase [LDH] and erythrocyte sedimentation rate [ESR]) and metabolic parameters (e.g., SUVmax of the biopsy site on PET/CT). Correlations between SUVmax and clinical variables and serum biochemical indicators were investigated.

Results

Of the 103 patients, 84 had NHL and 19 had Hodgkin lymphoma. The area under the receiver operating characteristic curve for examining the accuracy of SUVmax with regard to distinguishing between aggressive and indolent NHLs was 0.94 (95% confidence interval: 0.89-0.99), suggesting that SUVmax was a useful predictor of diagnosis. A cutoff value of 8.5 yielded a sensitivity of 76.3% and specificity of 92.0%. The SUVmax mean ± standard deviation of NHL (9.8 ± 6.0, range: 1.8-28.1) was higher than that of HL (7.5 ± 2.8, range: 3.5-13.9) (P = 0.016), but there was no statistically significant difference in SUVmax between NHL and HL (P > 0.05). SUVmax of the biopsy site was strongly positively correlated with Ki-67 index (r = 0.813, P < 0.001) and moderately positively correlated with IPI score (r = 0.332, P = 0.002), but it was not significantly correlated with clinical stage, LDH, or ESR (P > 0.05).

Conclusions

¹⁸F-FDG PET/CT may yield reliable measurements of tumor proliferation, and an SUVmax >8.5 may distinguish between aggressive and indolent NHLs. In adults with newly diagnosed lymphoma, SUVmax correlates with Ki-67 index and IPI score.

Evaluating Novel PET-CT Functional Parameters TLG and TMTV in Differentiating Low-grade Versus Grade 3A Follicular Lymphoma

BACKGROUND

Follicular lymphoma (FL) grading, low-grade 1-2 (LG) versus grade 3A (3A), informs management. However, accurate grading is challenging owing to disease heterogeneity and inter-reader variability. The [18F]-fluorodeoxyglucose positron emission tomography-computed tomography (PET-CT) parameter maximum standardized uptake value (SUVmax) has utility in differentiating LG from 3A FL, but the utility of novel parameters total lesion glycolysis (TLG) and total metabolic tumor volume (TMTV) is unknown.

PATIENTS AND METHODS

Retrospective review of diagnostic pre-treatment PET-CTs of patients aged > 18 years with FL grades 1-3A from 2009-2017 was performed. PET-CT parameters SUVmax, TLG, and TMTV values were generated using manual (MW) and semi-automated workflows (SW). Poisson regression and receiver operating characteristic curves were used to compare PET-CT parameters between LG and 3A.

RESULTS

A total of 49 patients with FL were identified: 38 LG and 11 3A. PET-CT parameters were significantly higher in 3A as compared with LG in both workflows. The cutoff values, sensitivities, and specificities were as follows: SUVmax: 10.4, 64%, and 74% in MW and 11.9, 73%, and 76% in SW; TLG: 543, 82%, and 74% in MW and 371, 73%, and 74% in SW; and TMTV: 141, 73%, and 76% in MW and 93, 64%, and 76% in SW. SUVmax had identical cutoff, sensitivity, and specificity across all 3 SWs, whereas TLG and TMTV had considerable variance across all 3 SWs.

CONCLUSIONS

TLG and TMTV are comparable to SUVmax in differentiating LG versus 3A FL. Cutoffs, sensitivities, and specificities varied in MW versus SW. Novel PET-CT parameters serve as reproducible adjuncts but not replacements for biopsy in differentiating grades of FL.

Radiochemical Approaches to Imaging Bacterial Infections: Intracellular versus Extracellular Targets

The discovery of penicillin began the age of antibiotics, which was a turning point in human healthcare. However, to this day, microbial infections are still a concern throughout the world, and the rise of multidrug-resistant organisms is an increasing challenge. To combat this threat, diagnostic imaging tools could be used to verify the causative organism and curb inappropriate use of antimicrobial drugs. Nuclear imaging offers the sensitivity needed to detect small numbers of bacteria in situ. Among nuclear imaging tools, radiolabeled antibiotics traditionally have lacked the sensitivity or specificity necessary to diagnose bacterial infections accurately. One reason for the lack of success is that the antibiotics were often chelated to a radiometal. This was done without addressing the ramifications of how the radiolabeling would impact probe entry to the bacterial cell, or the mechanism of binding to an intracellular target. In this review, we approach bacterial infection imaging through the lens of bacterial specific molecular targets, their intracellular or extracellular location, and discuss radiochemistry strategies to guide future probe development.

Pre-treatment maximum standardized uptake value predicts outcome after frontline therapy in patients with advanced stage follicular lymphoma

The impact of pre-treatment maximum standardized uptake value (SUV_max) on the outcome of follicular lymphoma (FL) following specific frontline regimens has not been explored. We performed a retrospective analysis of 346 patients with advanced stage follicular lymphoma (FL) without histological evidence of transformation, and analyzed the impact of SUV_max on outcome after frontline therapy. Fifty-two (15%) patients had a SUV_max >18, and a large lymph node ≥6 cm was the only factor associating with SUV_max >18 on multivariate analysis (odds ratio 2.7, 95% confidence interval [CI]: 1.3-5.3, P=0.006). The complete response rate was significantly lower among patients treated with non-anthracycline-based regimens if SUV_max was >18 (45% vs. 92%, P<0.001), but not among patients treated with R-CHOP (P=1). SUV_max >18 was associated with significantly shorter progression-free survival among patients treated with non-anthracycline-based regimens (77 months vs. not reached, P=0.02), but not among patients treated with R-CHOP (P=0.73). SUV_max >18 associated with shorter overall survival (OS) both in patients treated with R-CHOP (8-year OS 70% vs. 90%, P=0.02) and non-anthracycline-based frontline regimens (8-year OS 50% vs. 85%, P=0.001). In conclusion, pre-treatment PET scan has prognostic and predictive value in patients with advanced stage FL receiving frontline treatment.

Tumor Identification of Less Aggressive or Indolent Lymphoma With Whole-Body 11C-Acetate PET/CT

PURPOSE

The aim of this study was to investigate the diagnostic performance of whole-body [C]acetate PET/CT in less aggressive or indolent lymphomas, wherein [F]FDG PET/CT would exhibit limited sensitivity.

METHODS

Between September 2016 and May 2018, we prospectively evaluated 17 patients (9 men, 8 women; mean age [range], 71 [45-87] years) with pathologically proven less aggressive or indolent lymphomas according to Non-Hodgkin's Lymphoma Classification Project, using both [F]FDG PET/CT and [C]acetate PET/CT (performed on the same day). Detected nodal lesions were recorded according to the Ann Arbor classification. Extranodal (EN) lesions were also evaluated. We compared whole-body lesion detection between [F] FDG PET/CT and [C]acetate PET/CT using the McNemar test.

RESULTS

In all patients, significantly more nodal and EN lesions were detected using [C]acetate PET/CT than [F]FDG PET/CT (nodal: 84 vs 64 regions; P < 0.001; EN: 26 vs 19 regions, P = 0.039). Bone lesions were detected in 8 and 5 patients using [C]acetate PET/CT and [F]FDG PET/CT, respectively (P = 0.25). Among the 14 patients (82.4%) who underwent bone marrow biopsy, bone marrow involvement was detected with sensitivities of 100% (6/6 patients) and 80% (5/6 patients) using [C]acetate PET/CT and [F]FDG PET/CT, respectively. Multiple areas of focal uptake in the spleen of 1 patient were exhibited on [F]FDG PET/CT but not [C]acetate PET/CT.

CONCLUSIONS

[C]acetate PET/CT exhibited greater sensitivity than [F]FDG PET/CT for lesion detection in patients with less aggressive or indolent lymphomas, thus promising applicability as a physiological tracer in the study of such lesions.

Is True Whole-Body 18F-FDG PET/CT Required in Pediatric Lymphoma? An IAEA Multicenter Prospective Study

Guidelines recommend true whole-body ¹⁸F-FDG PET/CT scans from vertex to toes in pediatric lymphoma patients, although this suggestion has not been validated in large clinical trials. The objective of the study was to evaluate the incidence and clinical impact of lesions outside the "eyes to thighs" regular field of view (R-FOV) in ¹⁸F-FDG PET/CT staging (sPET) and interim (iPET) scans in pediatric lymphoma patients. Methods: True whole-body sPET and iPET scans were prospectively obtained in pediatric lymphoma patients (11 worldwide centers). Expert panel central review of sPET and iPET scans were evaluated for lymphoma lesions outside the R-FOV and clinical relevance of these findings. Results: A total of 610 scans were obtained in 305 patients. The sPET scans did not show lesions outside the R-FOV in 91.8% of the patients, whereas in 8.2% patients the sPET scans demonstrated lesions also outside the R-FOV (soft tissue, bone, bone marrow, and skin); however, the presence of these lesions did not change the clinical stage of any patient and did not affect treatment decision. Among the 305 iPET scans, there were no new positive ¹⁸F-FDG-avid lesions outside the R-FOV, when compared with their paired sPET scans. A single lesion outside the R-FOV on iPET occurred in 1 patient (0.3%), with the primary lesion diagnosed in the femur on sPET that persisted on iPET. Conclusion: The identification of additional lesions outside the R-FOV (eyes to thighs) using ¹⁸F-FDG PET/CT has no impact in the definition of the clinical stage of disease and minimal impact in the treatment definition of patients with pediatric lymphoma. As so, R-FOV for both sPET and iPET scans could be performed.

Comparison of Contrast-Enhanced Ultrasound and Positron Emission Tomography/Computed Tomography (PET/CT) in Lymphoma

Background

This study aimed to assess the value of contrast-enhanced ultrasound (CEUS) in the diagnosis and prognosis of lymphoma based on PET-CT.

Material/Methods

Our study included 88 superficial lymph nodes and 63 patients who underwent ultrasound-guided biopsy or surgery for pathology from October 2015 to March 2017. All lymph nodes were assessed by CEUS and PET-CT. CEUS and PET-CT parameters were recorded, including arrive time (AT), time to peak (TTP), base intensity (BI), peak intensity (PI), ascending slope (AS), descending slope (DS), area under the TIC curve (AUC), maximum standardized uptake value (SUVmax), and mean standardized uptake value (SUVmean). Pearson’s correlation was used to assess the associations of CEUS and PET-CT parameters.

Results

Of the 88 lymph nodes examined,12 were Hodgkin’s lymphoma (HL) and76 were non-Hodgkin’s lymphoma (NHL). The variations of CEUS dose parameters (ΔI, AUC, and AS) were positively correlated with PET-CT results (SUVmax and TLG). Correlation coefficients were 0.609, 0.518, 0.456, 0.630, 0.593, and 0. 532, respectively. The remaining time values (AT, TP, and ΔT) were negatively associated with PET-CT results. Correlation coefficients were −0.239, −0.272, −0.284and −0.377, −0.391, and −0.320, respectively.

Conclusions

Quantitative CEUS data were correlated with PET-CT values, with potential use in the diagnosis of lymphoma.

Outcome of patients with early-stage follicular lymphoma staged with 18F-Fluorodeoxyglucose (FDG) positron emission tomography (PET) and treated with radiotherapy alone

PURPOSE/OBJECTIVE(S)

To evaluate the impact of positron emission tomography (PET) staging on overall survival (OS) and progression-free survival (PFS) in patients with early-stage (stages I and II) follicular lymphoma (ESFL) treated with radiation therapy alone.

MATERIALS/METHODS

Eighty-five patients with ESFL treated with curative-intent radiation therapy (RT) between December 2000 and May 2011 were identified. Of those, 13 who had no PET staging and 25 who received additional systemic therapy were excluded from the analysis. Thus, we analyzed 47 patients with PET-staged ESFL treated with definitive radiation therapy alone (dose > 23Gy). Tumour features, pre-treatment computed tomography (CT) and PET stage, dose fractionation, and radiation therapy field extent were recorded. The Kaplan-Meier method was used to estimate the OS and PFS. Patterns of failure were assessed as cumulative incidences assuming competing risks.

RESULTS

Median age was 57 years (range 24-83); 43% were females. Most were PET stage 1 (76.6%). Median maximum nodal diameter was 3 cm. Median pre-treatment lactate dehydrogenase (LDH) was 327.5 (range 123-607, upper normal limit = 220). Twenty-six patients (55.3%) had infra-diaphragmatic disease. All received 30-36Gy in 15-24 fractions, with 59.6% treated with involved-field radiation therapy (IFRT) techniques. There was no significant difference in PFS between CT stage I and stage II (HR 1.30 95% CI [0.25-6.72], p = 0.75) with a 5-year PFS of 77% and 78% respectively. However, stage I on PET staging had a significantly better PFS than stage II (HR 4.66 95% CI [1.15-18.8], p = 0.038), with 5-year PFS of 84% and 60% respectively. Ten patients had recurrent disease, with distant disease being the first site of failure in seven patients. Seven-year OS was 91% (95% CI 79-100) for the whole cohort.

CONCLUSION

FDG-PET should be considered an essential element in the evaluation of patients with ESFL being considered for RT.

Whole-body MRI versus 18F-FDG PET/CT for pretherapeutic assessment and staging of lymphoma: a meta-analysis

Purpose

¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) positron emission tomography/computed tomography (PET/CT) is the reference standard in staging of ¹⁸F-FDG-avid lymphomas; however, there is no recommended functional imaging modality for indolent lymphomas. Therefore, we aimed to compare the performance of whole-body magnetic resonance imaging (WB-MRI) with that of ¹⁸F-FDG PET/CT for lesion detection and initial staging in patients with aggressive or indolent lymphoma.

Materials and methods

We searched the MEDLINE, EMBASE, and CENTRAL databases for studies that compared WB-MRI with ¹⁸F-FDG PET/CT for lymphoma staging or lesion detection. The methodological quality of the studies was assessed using version 2 of the “Quality Assessment of Diagnostic Accuracy Studies” tool. The pooled staging accuracy (μ) of WB-MRI and ¹⁸F-FDG PET/CT for initial staging and for assessing possible heterogeneity (χ²) across studies were calculated using commercially available software.

Results

Eight studies comprising 338 patients were included. In terms of staging, the meta-analytic staging accuracies of WB-MRI and ¹⁸F-FDG PET/CT for Hodgkin lymphoma and aggressive non-Hodgkin lymphoma (NHL) were 98% (95% CI, 94%–100%) and 98% (95% CI, 94%–100%), respectively. The pooled staging accuracy of ¹⁸F-FDG PET/CT dropped to 87% (95% CI, 72%–97%) for staging in patients with indolent lymphoma, whereas that of WB-MRI remained 96% (95% CI, 91%–100%). Subgroup analysis indicated an even lower staging accuracy of ¹⁸F-FDG PET/CT for staging of less FDG-avid indolent NHLs (60%; 95% CI, 23%–92%), in contrast to the superior performance of WB-MRI (98%; 95% CI, 88%–100%).

Conclusion

WB-MRI is a promising radiation-free imaging technique that may serve as a viable alternative to ¹⁸F-FDG PET/CT for staging of ¹⁸FDG-avid lymphomas, where ¹⁸F-FDG PET/CT remains the standard of care. Additionally, WB-MRI seems a less histology-dependent functional imaging test than ¹⁸F-FDG PET/CT and may be the imaging test of choice for staging of indolent NHLs with low ¹⁸F-FDG avidity.

Whole Body MRI and oncology: recent major advances

MRI is a very attractive approach for tumour detection and oncological staging with its absence of ionizing radiation, high soft tissue contrast and spatial resolution. Less than 10 years ago the use of Whole Body MRI (WB-MRI) protocols was uncommon due to many limitations, such as the forbidding acquisition times and limited availability. This decade has marked substantial progress in WB-MRI protocols. This very promising technique is rapidly arising from the research world and is becoming a commonly used examination for tumour detection due to recent technological developments and validation of WB-MRI by multiple studies and consensus papers. As a result, WB-MRI is progressively proposed by radiologists as an efficient examination for an expanding range of indications. As the spectrum of its uses becomes wider, radiologists will soon be confronted with the challenges of this technique and be urged to be trained in order to accurately read and report these examinations. The aim of this review is to summarize the validated indications of WB-MRI and present an overview of its most recent advances. This paper will briefly discuss how this examination is performed and which are the recommended sequences along with the future perspectives in the field.

Clinical management and outcomes of completely resected stage I follicular lymphoma

Recent studies have revealed the clinical and biological features of stage I follicular lymphoma (FL), but information about patients with stage I FL who underwent total resection after tissue biopsy is limited. Among 305 FL patients diagnosed between 2001 and 2013, clinical stage I disease was observed in 36 patients. Of these, 18 patients underwent total resection after diagnostic tissue biopsy. We used ¹⁸F-fluorodeoxyglucose positron emission CT for staging assessment in 13 of 18 patients (72.2%). The median age was 56.5 years. Six patients (33.3%) were male. The soluble interleukin-2 receptor alpha concentration was significantly lower than in patients with residual disease. Among these 18 patients, 7 patients (38.9%) were treated with a "watch-and-wait" (WW) policy, 7 (38.9%) were treated with involved-field irradiation, and 4 (22.2%) received systemic chemotherapy. Patients with resected disease were treated with significantly different strategies from those with residual disease (p = 0.0026). Five patients experienced relapse during follow-up (median follow-up: 48.2 months). All relapses were distant from the primary site, irrespective of treatment strategy. Among all stage I patients, disease resection was not a significant factor for survival (p = 0.9294). Collectively, the choice of treatment strategy was significantly influenced by patient status. Resection status was not significantly associated with survival after several treatment strategies.

Whole Body MRI and oncology: recent major advances

MRI is a very attractive approach for tumour detection and oncological staging with its absence of ionizing radiation, high soft tissue contrast and spatial resolution. Less than 10 years ago the use of Whole Body MRI (WB-MRI) protocols was uncommon due to many limitations, such as the forbidding acquisition times and limited availability. This decade has marked substantial progress in WB-MRI protocols. This very promising technique is rapidly arising from the research world and is becoming a commonly used examination for tumour detection due to recent technological developments and validation of WB-MRI by multiple studies and consensus papers. As a result, WB-MRI is progressively proposed by radiologists as an efficient examination for an expanding range of indications. As the spectrum of its uses becomes wider, radiologists will soon be confronted with the challenges of this technique and be urged to be trained in order to accurately read and report these examinations. The aim of this review is to summarize the validated indications of WB-MRI and present an overview of its most recent advances. This paper will briefly discuss how this examination is performed and which are the recommended sequences along with the future perspectives in the field.

Uptake Patterns of Untreated Primary Gastrointestinal Extranodal Lymphomas on Initial Staging 18F-FDG PET/CT and Metabolic Tumor Parameters

Objective:

Non-Hodgkin’s lymphomas arising from tissues other than primary lymphatic sites are classified as primary extranodal lymphomas (PEL). PELs of the gastrointestinal system (PGISL) originate from the lymphatic tissues within the gastrointestinal tract. The prognostic value of ¹⁸F-FDG PET/CT in lymphomas is high in terms of both overall survival (OS) and disease-free survival (DFS). Our aim was to investigate the uptake patterns and properties of low-grade and high-grade PGISL on primary staging ¹⁸F-FDG PET/CT, as well as the prognostic significance of metabolic tumor parameters in high grade PGISL.

Methods:

Thirty-nine patients with PGISL were enrolled in this retrospective cohort study between 2004-2015. Primary staging ¹⁸F-FDG PET/CT have been performed and quantitative parameters of SUV_max, SUV_mean, metabolic tumor volume (MTV), total lesion glycolysis (TLG) have been calculated for all patients prior to treatment. Low-grade and high-grade PGISL were compared in terms of metabolic tumor parameters. Cox regression models were performed to determine factors that correlate with DFS in high-grade PGISL.

Results:

There were statistically significant differences between high-grade and low-grade PGISL in terms of SUV_max, SUV_mean, MTV, TLG, recurrence, mortality, DFS and OS. None of the potential risk factors (sex, age, site, SUV_max, SUV_mean, MTV, TLG) for recurrence and metastasis in high grade PGISL was identified as a risk factor on univariate and multivariate Cox regression analysis.

Conclusion:

Metabolic tumor parameters are not predictive markers in high-grade PGISL, especially in diffuse large B cell variant and primary gastric lymphoma. The first implications suggest they will not play a role in patient management.

Patterns of use and survival outcomes of positron emission tomography for initial staging in elderly follicular lymphoma patients

The role of positron emission tomography (PET) in the initial assessment of follicular lymphoma (FL) has been a topic of debate. We examined the patterns of utilization of PET staging in FL and assessed the association of PET with survival. Using the SEER-Medicare database, we identified 5712 patients diagnosed with first primary FL between 2000 and 2009. Older age, African-American race, poor performance status, B-symptoms and history of anemia were negatively associated with PET staging. Receipt of PET staging was positively associated with treatment at institutions affiliated with research networks and with residence in areas with higher concentrations of nuclear medicine specialists. PET was associated with improved lymphoma-related (HR 0.69, 95% CI: 0.58-0.82) and overall (HR 0.75, 95% CI: 0.68-0.83) survival. Our findings substantiate the use of PET as the standard of care for imaging in FL patients. Further investigation is warranted to identify mechanisms underlying the apparent survival advantage associated with PET staging in FL.

Complete metabolic response (CMR) in positron emission tomography-computed tomography (PET-CT) scans may have prognostic significance in patients with marginal zone lymphomas (MZL)

Although clinical use of positron emission tomography-computed tomography (PET-CT) scans is well established in aggressive lymphomas, its prognostic value in marginal zone lymphoma (MZL) remains yet unclear. Hence, we investigated potential role of PET-CT in predicting MZL patients' outcomes following systemic chemotherapy. A total of 32 patients with MZL who received first-line chemotherapy were included in the analysis. They all underwent pretreatment, interim, and posttreatment PET-CT scans. The primary objective was to evaluate the role of complete metabolic response (CMR) in posttreatment PET-CT scans in predicting progression-free survival (PFS). Compared with non-CMR group, 5-year PFS rate was significantly higher in patients who achieved CMR in posttreatment PET-CT (54.2% vs 0.0%, P = .003) and also in patients gaining CMR in interim PET-CT scans (62.5% vs 15.6%, P = .026). Interestingly, early CMR group, who achieved and maintained CMR in both interim and posttreatment PET-CT scans, showed significantly higher 5-year PFS than those with delayed or never CMR group (62.5% vs 37.5% vs 0%, P = .008). Therefore, interim and/or posttreatment CMR can be prognostic at least in these subsets of patients with MZL treated with chemotherapy.

[18 F]-FDG PET/CT in the staging and management of indolent lymphoma: A prospective multicenter PET registry study

BACKGROUND

To measure the clinical impact of pretreatment fludeoxyglucose positron emission tomography/computed tomography (PET/CT) on the staging and management of apparent limited stage indolent lymphoma being considered for curative radiation therapy.

METHODS

We conducted a prospective multicenter registry study that included 197 patients accrued between May 1, 2012, and December 31, 2015. Pre-PET/CT stage, determined by clinical and CT data, was documented. If pre-PET/CT stage was indeterminate, a stage was assigned to the patient by the referring oncologist according to best clinical judgment and treatment intent. After PET/CT, revised stage and planned management were recorded and compared with data on actual treatment received available through provincial databases (n = 155).

RESULTS

PET/CT resulted in the upstaging of 47 (23.9%) patients with presumed limited stage disease (stage I-II) to advanced stage disease (stage III-IV) (P < .0001). Ten (5.1%) patients were downstaged by PET/CT, 4 of whom migrated from advanced to limited stage disease. Twenty-eight (14.2%) patients with a specific pre-PET/CT stage had equivocal PET/CT findings that required further evaluation to confirm disease extent. After PET/CT, 95 (61.3%) patients were planned to receive active treatment. Of the 59 patients planned for radiotherapy alone post-PET/CT, 34 (57.6%) received this treatment (P = .002), and nearly 80% of them (n = 27) had confirmed limited stage disease.

CONCLUSION

PET/CT has a significant impact on staging and management in patients with apparent limited stage indolent lymphoma who are being considered for curative radiotherapy. PET/CT should be routinely incorporated into the workup of these patients. Cancer 2017;123:2860-66. © 2017 American Cancer Society.

An overview of PET/MR, focused on clinical applications

Hybrid PET/MR scanners are innovative imaging devices that simultaneously or sequentially acquire and fuse anatomical and functional data from magnetic resonance (MR) with metabolic information from positron emission tomography (PET) (Delso et al. in J Nucl Med 52:1914-1922, 2011; Zaidi et al. in Phys Med Biol 56:3091-3106, 2011). Hybrid PET/MR scanners have the potential to greatly impact not only on medical research but also, and more importantly, on patient management. Although their clinical applications are still under investigation, the increased worldwide availability of PET/MR scanners, and the growing published literature are important determinants in their rising utilization for primarily clinical applications. In this manuscript, we provide a summary of the physical features of PET/MR, including its limitations, which are most relevant to clinical PET/MR implementation and to interpretation. Thereafter, we discuss the most important current and emergent clinical applications of such hybrid technology in the abdomen and pelvis, both in the field of oncologic and non-oncologic imaging, and we provide, when possible, a comparison with clinically consolidated imaging techniques, like for example PET/CT.

Can Positron Emission Tomography and Computed Tomography Be a Substitute for Bone Marrow Biopsy in Detection of Bone Marrow Involvement in Patients with Hodgkin's or Non-Hodgkin's Lymphoma?

Objective:

Positron emission tomography and computed tomography (PET/CT) has become an important part of staging and treatment evaluation algorithms of lymphoma. We aimed to compare the results of PET/CT with bone marrow biopsy (BMB) with respect to bone marrow involvement (BMI) in patients with Hodgkin’s lymphoma (HL) and aggressive non-Hodgkin’s lymphoma (aNHL).

Materials and Methods:

The medical files of a total of 297 patients diagnosed with HL or aNHL and followed at the hematology clinics of 3 major hospitals in İstanbul between 2008 and 2012 were screened retrospectively and 161 patients with classical HL and aNHL were included in the study. The patients were referred for PET/CT and BMB at the initial staging. BMB was performed as the reference standard for the evaluation of BMI.

Results:

There were 61 (38%) HL and 100 (62%) aNHL patients. Concordant results were revealed between PET/CT and BMB in 126 patients (78%) (52 HL, 74 aNHL), 20 with positive PET/CT and BMB results and 106 with negative PET/CT and BMB results. There were discordant results in 35 patients (9 HL, 26 aNHL), 16 of them with positive BMB and negative PET/CT results and 19 of them with negative BMB and positive PET/CT results.

Conclusion:

We observed that PET/CT is effective to detect BMI, despite it alone not being sufficient to evaluate BMI in HL and aNHL. Bone marrow trephine biopsy and PET/CT should be considered as mutually complementary methods for detection of BMI in patients with lymphoma. In suspected focal involvement, combining biopsy and PET/CT might improve staging results.

Systemic Front Line Therapy of Follicular Lymphoma: When, to Whom and How

The natural history of follicular lymphoma is usually characterized by an indolent course with a high response rate to the first line therapy followed by recurrent relapses, with a time to next treatment becoming shorter after each subsequent treatment line. More than 80% of patients have advanced stage disease at diagnosis. The time of initiation and the nature of the treatment is mainly conditioned by symptoms, tumor burden, lymphoma grading, co-morbidities and patients preference. A number of clinical and biological factors have been determined to be prognostic in this disease, but the majority of them could not show to be predictive of response to treatment, and therefore can’t be used to guide the treatment choice. CD20 expression is the only predictive factor recognized in the treatment of FL and justifies the use of “naked” or “conjugated” anti-CD20 monoclonal antibodies as a single agent or in combination with chemo- or targeted therapy. Nevertheless, as this marker is almost universally found in FL, it has little role in the choice of treatment. The outcome of patients with FL improved significantly in the last years, mainly due to the widespread use of rituximab, autologous and allogeneic transplantation in young and fit relapsed patients, the introduction of new drugs and the improvement in diagnostic accuracy and management of side effects. Agents as new monoclonal antibodies, immuno-modulating drugs, and target therapy have recently been developed and approved for the relapsed setting, while studies to evaluate their role in first line treatment are still ongoing. Here we report our considerations on first line treatment approach and on the potential factors which could help in the choice of therapy.

Advancing Precision Nuclear Medicine and Molecular Imaging for Lymphoma

PET with fluorodeoxyglucose F 18 (¹⁸F FDG-PET) is a meaningful biomarker for the detection, targeted biopsy, and treatment of lymphoma. This article reviews the evolution of ¹⁸F FDG-PET as a putative biomarker for lymphoma and addresses the current capabilities, challenges, and opportunities to enable precision medicine practices for lymphoma. Precision nuclear medicine is driven by new imaging technologies and methodologies to more accurately detect malignant disease. Although quantitative assessment of response is limited, such technologies will enable a more precise metabolic mapping with much higher definition image detail and thus may make it a robust and valid quantitative response assessment methodology.

Prognosis estimation under the light of metabolic tumor parameters on initial FDG-PET/CT in patients with primary extranodal lymphoma

Background

Non-Hodgkin’s lymphomas arising from the tissues other than primary lymphatic organs are named primary extranodal lymphoma. Most of the studies evaluated metabolic tumor parameters in different organs and histopathologic variants of this disease generally for treatment response. We aimed to evaluate the prognostic value of metabolic tumor parameters derived from initial FDG-PET/CT in patients with a medley of primary extranodal lymphoma in this study.

Patients and methods

There were 67 patients with primary extranodal lymphoma for whom FDG-PET/CT was requested for primary staging. Quantitative PET/CT parameters: maximum standardized uptake value (SUVmax), average standardized uptake value (SUVmean), metabolic tumor volume (MTV) and total lesion glycolysis (TLG) were used to estimate disease-free survival and overall survival.

Results

SUVmean, MTV and TLG were found statistically significant after multivariate analysis. SUVmean remained significant after ROC curve analysis. Sensitivity and specificity were calculated as 88% and 64%, respectively, when the cut-off value of SUVmean was chosen as 5.15. After the investigation of primary presentation sites and histo-pathological variants according to recurrence, there is no difference amongst the variants. Primary site of extranodal lymphomas however, is statistically important (p = 0.014). Testis and central nervous system lymphomas have higher recurrence rate (62.5%, 73%, respectively).

Conclusions

High SUVmean, MTV and TLG values obtained from primary staging FDG-PET/CT are potential risk factors for both disease-free survival and overall survival in primary extranodal lymphoma. SUVmean is the most significant one amongst them for estimating recurrence/metastasis.

The Evolving Role of Medical Imaging in Lymphoma Management: The Clinician's Perspective

Hodgkin and non-Hodgkin lymphomas are a heterogeneous group of hematologic neoplasms which arise from malignant lymphocytes. Imaging plays an important role in management of lymphoma patients during diagnosis, staging, and response assessment. Functional imaging may also provide prognostic information and improve the ability to detect extranodal disease. This article provides an overview of the evolving role of various imaging techniques in lymphoma from the clinician's perspective. It serves as an introduction to the other articles in this issue that focus on specific areas of lymphoma imaging.

(18) F-FDG PET-CT and trephine biopsy assessment of bone marrow involvement in lymphoma

The ability of positron emission tomography-computerized tomography (PET-CT) to accurately detect bone marrow involvement (BMI) has been suggested in Hodgkin lymphoma (HL) and diffuse large B-cell lymphoma (DLBCL), but its abilities in other histologies is less established. The aim of this retrospective study was to confirm the role of PET-CT in detecting BMI in DLBCL and HL, and to explore its usefulness in other subtypes. Of the 149 newly diagnosed patients, common subtypes included DLBCL, follicular lymphoma (FL) and HL. In DLBCL, the sensitivity and specificity of PET-CT at diagnosis were 75% and 92%. In FL, the sensitivity and specificity of PET-CT were 67% and 85% at diagnosis, and 73% and 89% at relapse. In HL, the sensitivity and specificity were 100% and 74%. PET-CT was able to detect BMI in patients with negative biopsies. Most of the patients in which PET-CT failed to identify BMI were already advanced stage by imaging. In this analysis, PET-CT was highly accurate for detecting BMI at diagnosis in DLBCL and HL and highly specific in FL at diagnosis and relapse. Results also suggested the diagnostic advantage of PET-CT over bone marrow biopsy in detecting BMI. Prospective evaluation is necessary and may eliminate biopsies in future patients.

Diagnosis of follicular lymphoma of the gastrointestinal tract: A better initial diagnostic workup

Due to an increasing incidence and more frequent recognition by endoscopists, gastrointestinal follicular lymphoma has been established as a variant of follicular lymphoma. However, due to its rarity, there are no established guidelines on the optimal diagnostic strategy for patients with primary gastrointestinal follicular lymphoma or secondary gastrointestinal involvement of systemic follicular lymphoma. This review offers an overview and pitfalls to avoid during the initial diagnostic workup of this disease entity. Previously reported case reports, case series, and retrospective studies are reviewed and focus on the disease's endoscopic and histological features, the roles of computed tomography and positron emission tomography scanning, the clinical utility of the soluble interleukin-2 receptor, and the possible pathogenesis.

Hematologic malignancies of the liver: spectrum of disease

The incidence of hematologic malignancies and their extranodal manifestations is continuously increasing. Previously unsuspected hepatic involvement in hematologic malignancies such as Hodgkin disease and non-Hodgkin lymphoma, posttransplant lymphoproliferative disorder, myeloid sarcoma (chloroma), multiple myeloma, Castleman disease, and lymphohistiocytosis may be seen by radiologists. Although the imaging features of more common hepatic diseases such as hepatocellular carcinoma, metastases, and infection may overlap with those of hepatic hematologic malignancies, combining the imaging features with clinical manifestations and laboratory findings can facilitate correct diagnosis. Clinical features that suggest a hematologic neoplasm as the cause of liver lesions include a young patient (<40 years of age), no known history of cancer, abnormal bone marrow biopsy results, fever of unknown origin, and night sweats. Imaging features that suggest hematologic malignancy include hepatosplenomegaly or splenic lesions, vascular encasement by a tumor without occlusion or thrombosis, an infiltrating mass at the hepatic hilum with no biliary obstruction, and widespread adenopathy above and below the diaphragm. Familiarity with the imaging features of hepatic hematologic malignancies permits correct provisional diagnosis and may influence therapeutic management. For example, when biopsy is performed, core biopsy may be needed in addition to fine-needle aspiration so that the tissue architecture of the neoplasm can be discerned. The predominant treatment of hematologic malignancies is chemotherapy or radiation therapy rather than surgery. Online supplemental material is available for this article.

Metabolism pathways in chronic lymphocytic leukemia

Alterations in chronic lymphocytic leukemia (CLL) cell metabolism have been studied by several investigators. Unlike normal B lymphocytes or other leukemia cells, CLL cells, like adipocytes, store lipids and utilize free fatty acids (FFA) to produce chemical energy. None of the recently identified mutations in CLL directly affects metabolic pathways, suggesting that genetic alterations do not directly contribute to CLL cells' metabolic reprogramming. Conversely, recent data suggest that activation of STAT3 or downregulation of microRNA-125 levels plays a crucial role in the utilization of FFA to meet the CLL cells' metabolic needs. STAT3, known to be constitutively activated in CLL, increases the levels of lipoprotein lipase (LPL) that mediates lipoprotein uptake and shifts the CLL cells' metabolism towards utilization of FFA. Herein, we review the evidence for altered lipid metabolism, increased mitochondrial activity and formation of reactive oxygen species (ROS) in CLL cells, and discuss the possible therapeutic strategies to inhibit lipid metabolism pathways in patient with CLL.

The value of 18F-FDG PET in pediatric patients with post-transplant lymphoproliferative disorder at initial diagnosis

PTLD is a serious complication of both solid organ and BMT. This study assessed whether (18) F-FDG PET, when added to CT scan, had additional value in the initial evaluation of PTLD in pediatric patients and whether PET/CT at baseline can reliably guide biopsy. This retrospective study evaluated 34 consecutive pediatric patients (14 female), aged 3.5-17.0 yr (mean age: 9.9 yr, s.d.: 4.9 yr), who had undergone (18) F-FDG PET/CT from May 2007 to December 2014 at initial diagnosis of PTLD following heart (n = 13), lung (n = 8), kidney (n = 4), liver (n = 3), liver and bowel (n = 3), and bone marrow (n = 3) transplantation. PTLD was diagnosed histopathologically in 33 patients and was based on clinical findings, elevated EBV, and imaging and follow-up results in one patient. On lesion-based analysis, (18) F-FDG PET showed more lesions than conventional CT scan (168 vs. 134), but CT revealed 22 lesions negative on PET. On per patient analysis, PET detected more lesions in 13 patients, CT identified more abnormalities in seven, and both showed the same number of lesions in 14. Adding (18) F-FDG PET to CT scans upstaged the disease in seven patients (20.5%). A combination of (18) F-FDG PET and CT was also useful in guiding biopsy, being positive in 36 of 39 samples (92.3%). These findings indicated that (18) F-FDG PET and CT are complementary at initial staging of pediatric PTLD and that (18) F-FDG PET/CT scanning can guide biopsies.

FDG PET/CT Response Assessment Criteria for Patients with Hodgkin's and Non-Hodgkin's Lymphoma at End of Therapy: A Multiparametric Approach

PURPOSE

Based on the International Harmonization Project (IHP) criteria, positron emission tomography (PET) response assessment of residual nodal masses in patients with lymphoma after completion of therapy is performed visually using mediastinal blood pool as the reference. The primary objective of this study was to define the optimal reference for PET response assessment. Secondary aim was to assess if morphological criteria on computed tomography (CT) may improve performance of PET.

METHODS

This institutional review board approved retrospective study included 137 patients, with Hodgkin's (n = 43) or non-Hodgkin's lymphoma (n = 94) assessed for residual masses (n = 180) after completion of therapy with pathology and clinical and imaging surveillance data (mean, 19 months) as the standard of reference. Two readers independently assessed response by IHP and Deauville criteria. The addition of morphological parameters on CT was assessed in relation to therapy response.

RESULTS

Based on the standard of reference, 36 patients (26.3 %) had residual lymphoma. For IHP and Deauville criteria, sensitivity, specificity and accuracy were 97.2 %, 97.2 % (p = 1); 79.2 %, 92.1 % (p < 0.001); and 83.9 %, 93.4 % (p = 0.001), respectively. Of the morphological parameters assessed, only change in size over course of therapy was significant (p < 0.003) and improved specificity for IHP-based interpretation to 90.4 % (p = 0.008).

CONCLUSIONS

Using liver as the visual reference to determine PET positivity for lymphoma patients being assessed for residual masses at the end of therapy improves specificity, yet maintains the high sensitivity of PET in identifying residual disease. The addition of change in size after therapy improves specificity of PET when using IHP-based but not Deauville-based interpretation.

PET/CT findings in a case with FDG-avid disseminated lacrimal gland MALToma with sequential development of large B-cell lymphoma and gastric MALToma

Primary orbital lymphomas are rare; the major histopathologic type is extranodal marginal-zone B-cell lymphoma of mucosa-associated lymphoid tissue (MALT) or MALToma. We present a case of a 79-year-old female patient with FDG-avid lacrimal gland MALToma with nodal and pulmonary involvement (stage IVE). Nasopharynx and gastric involvement were detected on restaging F-FDG PET/CT after rituximab therapy, and it was found to have a site of transformation to diffuse large B-cell lymphoma (DLBCL) in the nasopharynx. Gastric MALT lymphoma was also confirmed histopathologically, and she then underwent combination chemotherapy regimen, resulting in regression after 3 courses.

Whole-body diffusion-weighted MRI and (18)F-FDG PET/CT can discriminate between different lymphoma subtypes

AIM

To determine whether combined 2-[(18)F]-fluoro-2-deoxy-d-glucose ((18)F-FDG) positron-emission tomography (PET)/computed tomography (CT) and diffusion-weighted imaging (DWI) can be used for characterisation of different lymphoma subtypes, i.e., indolent versus aggressive lymphoma, and also to assess the prognostic value of different quantitative parameters of whole-body (WB) DWI and (18)F-FDG PET/CT.

MATERIALS AND METHODS

Pre-therapeutic WB magnetic resonance imaging (MRI) including DWI and (18)F-FDG PET/CT were performed in lymphoma patients. Different quantitative DWI and (18)F-FDG PET/CT parameters were evaluated for characterisation of different lymphoma subtypes. These parameters were also correlated, both separately and in combination, against overall survival (OS) and progression-free survival (PFS). A lesion-by-lesion analysis was performed for correlation analysis between maximum standardised uptake value (SUVmax), mean standardised uptake value (SUVmean) and mean apparent diffusion coefficient (ADC).

RESULTS

Fifty patients were included in the study and divided into three groups: Hodgkin's lymphoma (HL), n=12; aggressive non-Hodgkin's lymphoma (NHL), n=29 (including 20 patients with diffuse large B-cell lymphoma, DLBCL); and indolent NHL, n=9. Indolent NHL showed significantly lower mean ADC values than the other two lymphoma groups (p=0.013). Aggressive NHL had a higher SUVmax than HL. The OS analysis of all patients showed a relationship (p=0.006) between increased mean ADC and longer OS. A model with both SUVmean and mean ADC, strengthened the possibility to predict PFS; however, a separate analysis of the DLBCL patients showed that none of the quantitative parameters could predict OS or PFS.

CONCLUSION

ADC can discriminate between indolent and aggressive NHL. This finding can be useful in assessing possible transformation from indolent to aggressive NHL. ADC, ADC/SUV, and SUV cannot predict OS/PFS independent of lymphoma subtype.