Preliminary evidence of imaging of chemokine receptor-4-targeted PET/CT with [68Ga]pentixafor in non-Hodgkin lymphoma: comparison to [18F]FDG

New PET Tracers for Lymphoma

While functional imaging with [18F]Fluoro-deoxy-glucose positron emission tomography (PET)/computed tomography is a well-established imaging modality in most lymphoma entities, novel tracers addressing cell surface receptors, tumor biology, and the microenvironment are being developed. Especially, with the emergence of immuno-PET targeting surface markers of lymphoma cells, a new imaging modality of immunotherapies is evolving, which might especially aid in relapsed and refractory disease stages. This review highlights different new PET tracers in indolent and aggressive lymphoma subtypes and summarizes the current state of immuno-PET imaging in lymphoma.

Different extramedullary disease shown in chemokine receptor 4 targeted PET/CT with [ 68 Ga]Ga-pentixafor in patients with Waldenström macroglobulinemia and smoldering disease

INTRODUCTION

It is important to distinguish Waldenström macroglobulinemia from smoldering Waldenström macroglobulinemia (sWM), because only patients with Waldenström macroglobulinemia require treatment, however the distinction can be clinically complex. The aim of this study is to investigate whether [ 68 Ga]Ga-pentixafor PET/CT shows different characteristics in sWM and Waldenström macroglobulinemia patients and therefore can help to differentiate Waldenström macroglobulinemia and sWM.

RESULTS

Thirty-seven patients with newly diagnosed Waldenström macroglobulinemia and 11 sWM patients were analyzed [35 men and 13 women; 64.3 ± 10.7 (range, 29-87) years old]. The SUV max of bone marrow disease, lymph nodes, and other extramedullary diseases on [ 68 Ga]Ga-pentixafor were significantly higher than those on 2-[ 18 F]FDG PET/CT ( P  < 0.05). On [ 68 Ga]Ga-pentixafor PET/CT, patients with Waldenström macroglobulinemia had more lymph node regions involved, significantly higher incidence of involvement in more than three lymph node regions, larger nodal disease, and higher incidence of other extramedullary disease when compared with sWM patients ( P  < 0.05). Waldenström macroglobulinemia patients showed significantly higher total lesions uptake, total lesion volume, and SUV max of extramedullary disease than sWM patients did ( P  < 0.05). None of the visual or semiquantitative indexes in 2-[ 18 F]FDG PET/CT showed significant difference between Waldenström macroglobulinemia and sWM patients.

CONCLUSION

[ 68 Ga]Ga-pentixafor PET/CT had better diagnostic performance than 2-[ 18 F]FDG PET/CT in Waldenström macroglobulinemia. Patients with Waldenström macroglobulinemia presented with more extensive extramedullary disease shown in [ 68 Ga]Ga-pentixafor PET/CT than sWM patients did.

MALT Lymphoma in Histologic Transformation: FDG-Avid but Pentixafor-Negative

ABSTRACT

An 81-year-old woman experienced compression symptoms due to diffuse enlargement of the thyroid gland. The cytopathological results of thyroid fine-needle suggested malignancy. Therefore, she underwent bilateral thyroidectomy. Postoperative pathology indicated mucosa-associated lymphoid tissue (MALT) lymphoma. Three months later, she found a progressively enlarged mass in her neck. The biopsy showed MALT lymphoma with highly aggressive B-cell lymphoma transformation. 18F-FDG PET/CT showed increased metabolism in multiple lymph nodes. However, some of these lymph nodes were negative in 68Ga-pentxafor PET/CT. Our case demonstrated that 68Ga-pentixafor may have limited value in evaluating MALT lymphoma transformation.

Advances in PET Imaging of the CXCR4 Receptor: [68Ga]Ga-PentixaFor

[68Ga]Ga-PentixaFor, a PET agent targeting CXCR4 is emerging as a versatile radiotracer with promising applications in oncology, cardiology and inflammatory disease. Preclinical work in various cancer cell lines have demonstrated high specificity and selectivity. In human investigations of several tumors, the most promising applications may be in multiple myeloma, certain lymphomas and myeloproliferative neoplasms. In the nononcologic setting, [68Ga]Ga-PentixaFor could greatly improve detection for primary aldosteronism and other endocrine abnormalities. Similarly, atherosclerotic disease and other inflammatory conditions could also benefit from enhanced identification by CXCR4 targeting. Rapidly cleared from the body with a favorable imaging and radiation dosimetry profile that has been already studied in over 1000 patients, [68Ga]Ga-PentixaFor is a worthy agent for further clinical exploration with potential for theranostic applications in hematologic malignancies.

Chemokine Receptor PET/CT Provides Relevant Staging and Management Changes in Marginal Zone Lymphoma

Because of gastral and extranodal manifestations, guideline-compatible diagnostic work-up of marginal zone lymphoma is challenging. We aimed to determine the diagnostic performance of C-X-C motif chemokine receptor 4 (CXCR4)-directed PET/CT compared with routine diagnostics, along with PET/CT-based retrospective changes in therapeutic management. The predictive potential of the PET signal was also investigated, and the number of patients eligible for CXCR4-directed radioligand therapy in a theranostic setting was determined. Methods: For this study, 100 marginal zone lymphoma patients underwent CXCR4-directed PET/CT. We compared staging results and treatment decisions from molecular imaging with respective results from guideline-compatible work-up (CT, esophagogastroduodenoscopy, and bone marrow-derived biopsy). Prognostic performance of the in vivo CXCR4 PET signal for progression-free survival (PFS) was evaluated (using log-rank test and Kaplan-Meier curves). Results: Relative to CT, CXCR4-directed imaging led to Ann Arbor (AA) staging changes for 27 of 100 patients (27.0%). Among those, clinically relevant upstaging from AA I or AA II to AA III or AA IV was observed for 23 patients (85.2%), along with respective changes in therapeutic management (escalation, 6/23 [26.1%]; deescalation, 17/23 [73.9%]). CXCR4 PET/CT yielded diagnostic accuracy of 94.0% relative to esophagogastroduodenoscopy and 76.8% relative to bone marrow-derived biopsy. An increased CXCR4 PET signal was linked to shorter PFS (707 d vs. median PFS not reached; hazard ratio, 3.18; 95% CI, 1.37-7.35; P = 0.01). CXCR4-directed radioligand therapy would have been feasible for 18 of 100 patients (18.0%). Conclusion: Relative to CT, CXCR4-directed PET/CT led to AA changes for 27 of 100 patients. Chemokine receptor PET/CT may improve current diagnostic algorithms and influence management relative to CT alone, potentially obviating some biopsies.

Lymphoma-Sink Effect in Marginal Zone Lymphoma Based on CXCR4-Targeted Molecular Imaging

PURPOSE

Recent studies investigating a tumor-sink effect in solid tumors reported on decreasing uptake in normal organs in patients with higher tumor burden. This phenomenon, however, has not been evaluated yet for theranostic radiotracers applied to hematological neoplasms. As such, we aimed to determine a potential "lymphoma-sink effect" in patients with marginal zone lymphoma (MZL) imaged with C-X-C motif chemokine receptor (CXCR) 4-directed PET/CTs.

PROCEDURES

We retrospectively analyzed 73 patients with MZL who underwent CXCR4-directed [⁶⁸Ga]Ga-PentixaFor PET/CT. Normal unaffected organ uptake (heart, liver, spleen, bone marrow, kidneys) was quantified using volumes of interests (VOIs) and mean standardized uptake values (SUV_mean) were derived. MZL manifestations were also segmented to determine the maximum and peak standardized uptake values SUV (SUV_max/peak) and volumetric parameters, including lymphoma volume (LV), and fractional lymphoma activity (FLA, defined as LV*SUV_mean of lymphoma burden). This approach resulted in 666 VOIs to capture the entire MZL manifestation load. We used Spearman's rank correlations to determine associations between organ uptake and CXCR4-expressing lymphoma lesions.

RESULTS

We recorded the following median SUV_mean in normal organs: heart, 1.82 (range, 0.78-4.11); liver, 1.35 (range, 0.72-2.99); bone marrow, 2.36 (range, 1.12-4.83); kidneys, 3.04 (range, 2.01-6.37); spleen, 5.79 (range, 2.07-10.5). No relevant associations between organ radiotracer uptake and MZL manifestation were observed, neither for SUV_max (ρ ≤ 0.21, P ≥ 0.07), SUV_peak (ρ ≤ 0.20, P ≥ 0.09), LV (ρ ≤ 0.13, P ≥ 0.27), nor FLA (ρ ≤ 0.15, P ≥ 0.33).

CONCLUSIONS

Investigating a lymphoma-sink effect in patients with hematological neoplasms, we observed no relevant associations between lymphoma burden and uptake in normal organs. Those observations may have therapeutic implications, e.g., for "cold" SDF1-pathway disrupting or "hot," CXCR4-directed radiolabeled drugs, as with higher lymphoma load, normal organ uptake seems to remain stable.

FDG-PET/CT in the Monitoring of Lymphoma Immunotherapy Response: Current Status and Future Prospects

Cancer immunotherapy has been extensively investigated in lymphoma over the last three decades. This new treatment modality is now established as a way to manage and maintain several stages and subtypes of lymphoma. The establishment of this novel therapy has necessitated the development of new imaging response criteria to evaluate and follow up with cancer patients. Several FDG PET/CT-based response criteria have emerged to address and encompass the various most commonly observed response patterns. Many of the proposed response criteria are currently being used to evaluate and predict responses. The purpose of this review is to address the efficacy and side effects of cancer immunotherapy and to correlate this with the proposed criteria and relevant patterns of FDG PET/CT in lymphoma immunotherapy as applicable. The latest updates and future prospects in lymphoma immunotherapy, as well as PET/CT potentials, will be discussed.

C-X-C Motif Chemokine Receptor 4-Targeted Radioligand Therapy in Patients with Advanced T-Cell Lymphoma

C-X-C motif chemokine receptor 4 (CXCR4)-targeted radioligand therapy (RLT) has already been applied to advanced blood cancers, such as multiple myeloma or diffuse large B-cell lymphoma. We present a series of patients with advanced T-cell lymphoma (TCL) who were scheduled for CXCR4-directed therapy as a conditioning regimen, followed by hematopoietic stem cell transplantation (HSCT). Methods: Four patients with advanced, heavily pretreated, and relapsed TCL (2 men, 2 women; median age, 50 y) without suitable alternative therapeutic options underwent CXCR4-directed PET and pretherapeutic dosimetry. We then conducted CXCR4-targeted RLT in combination with allogeneic (3/4, 75%) or autologous (1/4, 25%) HSCT. One patient also underwent radioimmunotherapy targeting CD66 to enhance therapeutic efficacy. We investigated safety, best response, progression-free survival, and overall survival. Results: Pretherapeutic dosimetry indicated lymphoma-absorbed doses of up to 33.2 Gy from CXCR4-targeted RLT. Except for 1 patient who developed tumor lysis syndrome along with transient grade 3 kidney failure, no acute toxicity, allergic reactions, or other adverse events were recorded during therapy. One patient developed septicemia and subsequently died 16 d after RLT, whereas engraftment was achieved in the remaining 3 patients (75%). During follow-up, a partial response was recorded in 1 of 3 patients (33.3%) and a complete metabolic response in the other two (66.7%, with 1 patient also receiving additional radioimmunotherapy). Median progression-free survival was 7 mo (range, 4-25 mo). After a median follow-up of 54 mo (range, 4-56 mo), 3 patients were still alive at the date of censoring. Conclusion: For advanced, heavily pretreated TCL, CXCR4-directed RLT may serve as an effective conditioning therapy before HSCT and can cause substantial antilymphoma activity, leading to a remarkable response in selected cases.

Myocardial Uptake of 68Ga-Pentixafor in a Patient With Systemic Amyloidosis

ABSTRACT

A 55-year-old man presented with chest tightness and lower-limb edema for 1 year. Laboratory and imaging examinations suggested cardiac amyloidosis. Both 18F-FDG and 68Ga-pentixafor PET/CT showed increased uptake in the myocardium of the left ventricle, whereas the bone marrow had diffusely mild uptake of 68Ga-pentixafor without bone destruction. 99mTc-MDP bone scintigraphy also detected extraosseous uptake in the heart, gut, kidneys, and soft tissue. The biopsy of the abdominal subcutaneous fat confirmed amyloid deposits, and the patient was finally diagnosed with primary systemic amyloidosis. This case demonstrated that cardiac amyloidosis might show increased 68Ga-pentixafor uptake in myocardium.

Intense 68 Ga-Pentixafor Activity in Idiopathic Retroperitoneal Fibrosis

ABSTRACT

A 52-year-old man was admitted to our hospital with lower abdominal and low back pain, and abdomen CT at an outside hospital presented a retroperitoneal mass with left urinary tract obstruction and hydronephrosis. In 68 Ga-pentixafor PET/CT, the retroperitoneal mass showed intense radioactivity. Subsequently, the patient underwent biopsy of the retroperitoneal mass. The pathological examination showed only fibrous tissue without tumor cells. The patient was finally diagnosed with idiopathic retroperitoneal fibrosis. Our case demonstrated that idiopathic retroperitoneal fibrosis had intense uptake of 68 Ga-pentixafor.

The Role of [68Ga]Ga-Pentixafor PET/CT or PET/MRI in Lymphoma: A Systematic Review

The aim of this systematic review was to investigate published data about the role of gallium-68 Pentixafor positron emission tomography/computed tomography ([⁶⁸Ga]Ga-Pentixafor PET/CT) or PET/magnetic resonance imaging (PET/MRI) in patients affected by lymphoma. A comprehensive computer literature search of the Scopus, PubMed/MEDLINE, and Embase databases was conducted including articles indexed up to June 2022. In total, 14 studies or subsets in studies were eligible for inclusion. From the analyses of the selected studies, the following main findings have been found: (1) lymphomas can be considered [⁶⁸Ga]Ga-Pentixafor avid diseases, also in cases of fluorine-18 fluorodeoxyglucose [¹⁸F]FDG-not avid forms such as lymphoplasmacytic lymphoma (LPL), chronic lymphocytic leukemia (CLL), marginal zone lymphoma (MZL) and central nervous system lymphoma (CNSL); (2) among lymphomas, mantle cell lymphoma (MCL) and MZL are those with highest [⁶⁸Ga]Ga-Pentixafor uptake; (3) [⁶⁸Ga]Ga-Pentixafor PET/CT or PET/MRI is a useful tool for the staging and treatment response evaluation; (4) [⁶⁸Ga]Ga-Pentixafor PET seems to have a better diagnostic performance than [¹⁸F]FDG PET in evaluating lymphomas. Despite several limitations affecting this analysis, especially related to the heterogeneity of the included studies, [⁶⁸Ga]Ga-Pentixafor PET may be considered a useful imaging method for staging and treatment response evaluation of several lymphomas, especially MZL, CNSL and LPL.

Positron Emission Tomography Molecular Imaging for Phenotyping and Management of Lymphoma

Positron emission tomography (PET) represents molecular imaging for non-invasive phenotyping of physiological and biochemical processes in various oncological diseases. PET imaging with ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) for glucose metabolism evaluation is the standard imaging modality for the clinical management of lymphoma. One of the ¹⁸F-FDG PET applications is the detection and pre-treatment staging of lymphoma, which is highly sensitive. ¹⁸F-FDG PET is also applied during treatment to evaluate the individual chemo-sensitivity and accordingly guide the response-adapted therapy. At the end of the therapy regiment, a negative PET scan is indicative of a good prognosis in patients with advanced Hodgkin's lymphoma and diffuse large B-cell lymphoma. Thus, adjuvant radiotherapy may be alleviated. Future PET studies using non-¹⁸F-FDG radiotracers, such as ⁶⁸Ga-labeled pentixafor (a cyclic pentapeptide that enables sensitive and high-contrast imaging of C-X-C motif chemokine receptor 4), ⁶⁸Ga-labeled fibroblast activation protein inhibitor (FAPI) that reflects the tumor microenvironment, and ⁸⁹Zr-labeled atezolizumab that targets the programmed cell death-ligand 1 (PD-L1), may complement ¹⁸F-FDG and offer essential tools to decode lymphoma phenotypes further and identify the mechanisms of lymphoma therapy.

Burkitt Lymphoma/Leukemia Presented on 68Ga-Pentixafor and 18F-FDG PET/CT

ABSTRACT

An 18-year-old man with newly diagnosed Burkitt lymphoma/leukemia was referred for 18F-FDG and 68Ga-Pentixafor PET/CT. 68Ga-Pentixafor PET/CT revealed similar radioactivity uptake pattern to the 18F-FDG PET/CT in superior phrenic lymph node, ascending colon, ileocecum, peritoneal, marrow, and spleen. This case highlighted that it might be interesting to further investigate the role of 68Ga-Pentixafor PET/CT imaging in staging, treatment evaluation, and especially the feasibility of CXCR4-directed radioligand therapy in Burkitt lymphoma with positive expression of CXCR4.

Semi-quantitative measurements of chemokine receptor 4-targeted 68Ga-pentixafor PET/CT in response assessment of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma

Purpose

⁶⁸Ga-pentixafor PET/CT was reported to have a high sensitivity in detecting tumor involvement of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) in our previous study. We aimed to further investigate the semi-quantitative measurements of ⁶⁸Ga-pentixafor PET/CT in response assessment in WM/LPL.

Methods

Fifteen patients with WM/LPL were recruited in a prospective cohort study and underwent both ⁶⁸Ga-pentixafor and ¹⁸F-FDG PET/CT at baseline and post-treatment. PET/CT-based responses were analyzed with semi-quantitative assessments of metabolic tumor volume (MTV) and total lesions glycolysis/uptake (TLG_FDG and TLU_CXCR4), and the correlation between PET/CT-based response and clinical response, monoclonal protein and IgM response was analyzed.

Results

After chemotherapy, 5 patients had complete response or very good partial response, 8 had partial response or minimal response and 2 had progressive disease. In quantitative analysis, ⁶⁸Ga-pentixafor PET/CT-based response (measured in ∆TLU_CXCR4%, ∆MTV_CXCR4%, ∆SUVpeak%) showed a significant direct correlation with clinical response, monoclonal protein and IgM response (p < 0.01). However, ¹⁸F-FDG PET/CT-based response was independent from clinical response (p > 0.05).

Conclusions

The semi-quantitative measurements of ⁶⁸Ga-pentixafor PET/CT outperformed ¹⁸F-FDG PET/CT in response assessment of WM/LPL.

Supplementary Information

The online version contains supplementary material available at 10.1186/s13550-021-00852-0.

FDG-PET/CT in Lymphoma: Where Do We Go Now?

18F-fluorodeoxyglucose positron emission tomography combined with computed tomography (FDG-PET/CT) is an essential part of the management of patients with lymphoma at staging and response evaluation. Efforts to standardize PET acquisition and reporting, including the 5-point Deauville scale, have enabled PET to become a surrogate for treatment success or failure in common lymphoma subtypes. This review summarizes the key clinical-trial evidence that supports PET-directed personalized approaches in lymphoma but also points out the potential place of innovative PET/CT metrics or new radiopharmaceuticals in the future.

Chemokine Receptor 4-Targeted 68Ga-Pentixafor PET/CT in Response Assessment of Waldenström Macroglobulinemia/Lymphoplasmacytic Lymphoma: Comparison to 18F-FDG PET/CT

PURPOSE

68Ga-pentixafor PET/CT was reported to have a high sensitivity in detecting tumor involvement of Waldenström macroglobulinemia/lymphoplasmacytic lymphoma (WM/LPL) in our previous study. We aimed to further investigate its value in response assessment in WM/LPL.

PATIENTS AND METHODS

Fifteen patients with WM/LPL were recruited in a prospective cohort study and underwent both 68Ga-pentixafor and 18F-FDG PET/CT at baseline and posttreatment. PET/CT-based responses were analyzed with visual assessments and compared with clinical response.

RESULTS

At baseline, all of the 15 patients had a positive 68Ga-pentixafor PET/CT scan, whereas 18F-FDG PET/CT was positive in 11/15 patients. After chemotherapy, the overall response rate was 86.7% (13/15), and 68Ga-pentixafor PET/CT showed different degree of tumor response from baseline in these patients. In the 2 patients with progressive disease, 68Ga-pentixafor PET/CT detected new lesions or remarkable increase of 68Ga-pentixafor uptake in tumor involvements. However, 18F-FDG PET/CT failed to detect the improvement of disease in 6/13 patients and missed disease progression in 1 of the 2 patients.

CONCLUSIONS

68Ga-pentixafor PET/CT outperformed 18F-FDG PET/CT in response assessment of WM/LPL.

Increased Uptake of 68Ga-Pentixafor in Thymic Rebound After Chemotherapy in a Patient With Multiple Myeloma

A 38-year-old man with newly diagnosed multiple myeloma underwent Ga-pentixafor PET/CT for baseline assessment. Ga-pentixafor PET/CT demonstrated multiple focal bone and bone marrow lesions with intense radioactivity. After 9 cycles of chemotherapy against multiple myeloma, the patient experienced serologically complete remission of myeloma. Consistently, the follow-up Ga-pentixafor PET/CT for PET response showed significantly reduced uptake in the previously chemokine receptor 4-positive bone lesions. However, intense and homogeneous uptake of Ga-pentixafor was noted in the thymus with a smooth contour and slightly increased density, which is possibly caused by thymic hyperplasia after chemotherapy.