Somatostatin Receptors and Chemokine Receptor CXCR4 in Lymphomas: A Histopathological Review of Six Lymphoma Subtypes

Chemokine receptor-targeted PET/CT provides superior diagnostic performance in newly diagnosed marginal zone lymphoma patients: a head-to-head comparison with [18F]FDG

BACKGROUND

In patients with marginal zone lymphoma (MZL), [18F]FDG PET/CT provided inconsistent diagnostic accuracy. C-X-C motif chemokine receptor 4 (CXCR4) is overexpressed in MZL and thus, may emerge as novel theranostic target. We aimed to evaluate the diagnostic performance of CXCR4-targeting [68Ga]Ga-PentixaFor when compared to [18F]FDG PET/CT in MZL.

METHODS

Thirty-two untreated MZL patients (nodal, n = 17; extranodal, n = 13; splenic, n = 2) received [68Ga]Ga-PentixaFor and [18F]FDG PET/CT within median 2 days. We performed a visual and quantitative analysis of the total lymphoma volume by measuring maximum/peak standardized uptake values (SUVmax/peak), and calculating target-to-background ratios (TBR, defined as lesion-based SUVpeak divided by SUVmean from blood pool). Visual comparisons for both radiotracers were carried out for all target lesions (TL), and quantitative analysis of concordant TL evident on both scans. Last, MZL subtype analyses were also conducted.

RESULTS

On a patient-based level, [68Ga]Ga-PentixaFor identified MZL manifestations in 32 (100%) subjects (vs. [18F]FDG, 25/32 [78.1%]). Of the 256 identified TL, 127/256 (49.6%) manifestations were evident only on CXCR4-directed imaging, while only 7/256 (2.7%) were identified on [18F]FDG but missed by [68Ga]Ga-PentixaFor. In the remaining 122/256 (47.7%) concordant TL, [68Ga]Ga-PentixaFor consistently provided increased metrics when compared to [18F]FDG: SUVmax, 10.3 (range, 2.53-37.2) vs. 5.72 (2.32-37.0); SUVpeak, 6.23 (1.58-25.7) vs. 3.87 (1.54-27.7); P < 0.01, respectively. Concordant TL TBR on [68Ga]Ga-PentixaFor (median, 3.85; range, 1.05-16.0) was also approximately 1.8-fold higher relative to [18F]FDG (median, 2.08; range, 0.81-28.8; P < 0.01). Those findings on image contrast, however, were driven by nodal MZL (P < 0.01), and just missed significance for extranodal MZL (P = 0.06).

CONCLUSIONS

In newly diagnosed MZL patients, [68Ga]Ga-PentixaFor identified more sites of disease when compared to [18F]FDG, irrespective of MZL subtype. Quantitative PET parameters including TBR were also higher on [68Ga]Ga-PentixaFor PET/CT, suggesting improved diagnostic read-out using chemokine receptor-targeted imaging.

First reported case of splenic diffuse red pulp small B-cell lymphoma with novel mutations in CXCR4 and TRAF3 genes

Splenic diffuse red pulp small B-cell lymphoma (SDRPL) is a rare B-cell tumor whose genetic characteristics are poorly understood. Here, we introduce the case of a 62-year-old patient with SDRPL who showed progressive elevation of lymphocytes and progressive spleen enlargement. Immunohistochemistry showed that CD20 and CD79a were positive, and the Ki-67 labelling index was approximately 5%, consistent with the pathological features of splenic B-cell lymphoma. Spleen tissue and peripheral blood samples from the patient were sequenced using a next-generation sequencing platform, and mutations possibly were detected in the CXCR4 and TRAF3 genes that may be related to the pathogenesis of the disease. This finding may provide insights into the molecular pathogenesis of SDRPL and assist in molecular diagnosis and targeted therapy for SDRPL.

Evaluation of [68Ga]-DOTATOC PET/MRI in Patients with Meningioma of the Subcranial and Intraorbital Space

Meningiomas are known to express somatostatin receptor (SSTR) type 2 to a high degree. Therefore, radiolabeled somatostatin analogs, such as DOTATOC, have been introduced for PET imaging of meningiomas. However, the benefit of hybrid SSTR PET/MRI is still debated. Here, we report our experience with [⁶⁸Ga]-DOTATOC PET/MRI. Methods: PET/MRI was performed in 60 patients with suspected or diagnosed meningiomas of the skull plane and eye socket. Acquired datasets were reported by 2 independent readers regarding local tumor extent and signal characteristics. Histopathologic results and follow-up imaging served as the reference standard. SUVs of target lesions were analyzed according to the corresponding maximal tracer uptake. The diagnostic accuracy of PET/MRI and conventional MRI was determined independently and compared with the reference standard. Results: In total, 60 target lesions were identified, with 54 considered to be meningiomas according to the reference standard. Sensitivity and specificity of PET/MRI versus MRI alone were 95% versus 96% and 75% versus 66%, respectively. The McNemar test was not able to distinguish any differences between PET/MRI and the reference standard or MRI and the reference standard. No differences were found between the 2 modalities with respect to local infiltration. Conclusion: SSTR PET/MRI and MRI yielded similar accuracy for the detection of meningiomas of the skull base and intraorbital space. Here, sequential low-dose SSTR PET/CT might be helpful for the planning of radioligand therapy or radiotherapy.

Repurposed Effect of 177Lu-DOTATATE in the Treatment of Mantle Cell Lymphoma

Mantle cell lymphoma (MCL) is an uncommon subcategory of non-Hodgkin lymphoma (NHL). Pathogenesis primarily includes overexpression of CCND1 and SOX11 along with other molecular aberrations. Lutetium ¹⁷⁷Lu-DOTATATE is a radiolabeled somatostatin analogue used for the treatment of gastrointestinal neuroendocrine tumors. There are no clinical data supporting the use of Lutetium ¹⁷⁷Lu-DOTATATE in the treatment of lymphoma. We describe the case of an 84-year-old man with a history of MCL and carcinoid tumor of the lung. Following progression of the carcinoid malignancy, the patient was treated with Lutetium ¹⁷⁷Lu-DOTATATE. After treatment, there was an overall improvement of the patient's MCL that was demonstrated by stable lymphadenopathy on serial CT scans and down-trend of the absolute lymphocyte count. Therefore, we hypothesize that ¹⁷⁷Lu-DOTATATE might have a role and can be repurposed for treating MCL.