Background/Purpose: Primary Sjögren’s syndrome (pSS) patients have an increased risk of developing a lymphoma. PSS-associated lymphomas are mostly of the mucosa associated lymphoid tissue (MALT) type and most commonly arise within the parotid glands. Although fluorine-18-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) is widely used in oncology and inflammatory diseases, the usefulness of FDG-PET/CT in detecting pSS-associated lymphomas is not yet clear. Therefore, we aimed to assess the usefulness of FDG-PET/CT for the diagnosis of pSS associated lymphomas in a large retrospective cohort of pSS patients.

Methods: PSS patients fulfilling the ACR-EULAR criteria for pSS, who underwent FDG-PET/CT between 2010 and 2021, were recruited from the electronic patient file system of the University Medical Center Groningen. Patients were excluded if FDG-PET/CT was performed due to an intercurrent malignancy not related to pSS. All FDG-PET/CT scans were performed on integrated PET/CT camera systems (Siemens Biograph mCT or Vision) and were reconstructed according to standardized European guidelines. FDG-PET/CT scans were visually and semi-quantitatively analysed by two investigators, focusing on the uptake in salivary and lacrimal glands and lymph nodes. Furthermore, systemic disease activity was assessed in the organs that can be visualized by FDG-PET/CT.

Results: Of the 71 included pSS patients, 26 (37%) were histologically diagnosed with a lymphoma. 23 (88%) of the pSS-associated lymphomas were of the MALT type; biopsy location: parotid (N=17), lacrimal gland (N=2), lungs (N=2) and lymph node (N=2). The maximum standardized uptake value (SUVmax) and the SUVpeak were significantly higher in both the parotid and the submandibular glands of pSS patients with lymphoma (p< 0.001 for both parameters in both glands). Furthermore, patients with lymphoma more often showed presence of nodular lung lesions, compared to non-lymphoma patients (31% vs 7%, p=0.014). There was no significant difference in the presence of abnormal FDG-uptake in lymph nodes (81% for lymphoma vs 70% for non-lymphoma). Furthermore, no differences were found in the presence of arthritis, myositis, enthesopathy, vasculitis, nephritis or interstitial lung disease, and lymphoma patients did not more frequently show abnormal uptake in the thyroid gland, liver, spleen or pancreas, compared to non-lymphoma patients.

Conclusion: PSS patients with lymphoma have significantly higher SUV-values in both the parotid and submandibular glands, and more often show nodular lung lesions. Standardized FDG-PET/CT can be useful in the diagnostic work-up of pSS-associated lymphomas, since (1) it can assist in the decision if, and subsequently at which location, a biopsy is needed, and (2) it could reduce the number of biopsies in patients who do not have salivary gland FDG-PET/CT abnormalities nor presence of nodular lung lesions. Importantly, abnormal uptake in lymph node regions is frequent in pSS and does not discriminate between lymphoma and non-lymphoma.

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ACR Meeting Abstracts - https://acrabstracts.org/abstract/the-value-of-fdg-pet-ct-in-the-detection-of-lymphomas-associated-with-primary-sjogrens-syndrome/