Lymphoma Associated With High Parotid Uptake and Pulmonary Lesions on PET-CT in Primary Sjogren Syndrome

In patients with primary Sjogren syndrome (pSS), a lymphoma diagnosis was associated with focal lung lesions or maximum parotid gland uptake on Fluorine 18 (¹⁸F) fluorodeoxyglucose (FDG) positron emission tomography with computed tomography (PET-CT), according to a report published in Arthritis & Rheumatology.

Despite that patients with pSS with systemic manifestations often display PET-CT abnormalities in the lungs, lymph nodes, and salivary glands regardless of lymphoma status, ¹⁸F-FDG PET-CT may still be useful for identifying lymphoma-associated patterns during imaging, although its utility remains unclear. Investigators sought to evaluate the usefulness of PET-CT for this purpose by comparing and characterizing patients with pSS with and without lymphoma in the largest study of its kind to date.

A dual-center retrospective study enrolled 45 participants with pSS who had undergone ¹⁸F-FDG PET-CT between 2011 and 2017 for either suspicion (n=37) or staging (n=8) of lymphoma. This cohort was divided into 2 groups: those with lymphoma (n=15; mean age, 61.0 years; 80.0% women) and those without lymphoma (n=30; mean age, 63.0 years; 83.3% women). Two readers blinded to lymphoma diagnosis assessed the PET-CT scans and compared abnormalities between the 2 study groups.

When compared with those without lymphoma, participants diagnosed with lymphoma had higher mean parotid gland size (P =.048) and an increased parotid maximum standardized uptake value, in addition to greater frequency of salivary gland enlargement (P =.003). However, no significant differences were found between the 2 groups in terms of the size, pattern, or frequency of lymphadenopathy, with uptake occurring in 53.3% and 43.3% of lymph nodes in patients with and without lymphoma, respectively.

Pulmonary uptake — in the form of focal nodules or condensations — was seen in 5 (33.3%) and 1 (3.3%) patients with and without lymphoma, respectively (P =.01). The whole PET-CT maximum standardized uptake value was higher in people with lymphoma vs those without (6.3 vs 4.2; P =.02), and the activity-derived median PET score was also greater in those with lymphoma (4 vs 2; P =.04).

Receiver operating characteristic curve analysis showed that a maximum standardized uptake value of ≥4.7 in the parotid glands and ≥5.7 in other sites, as well as focal pulmonary lesions, were predictive of lymphoma. Of these 3 parameters, the combination of parotid gland uptake ≥4.7 and focal lung lesions was deemed the most highly suggestive of lymphoma, with a sensitivity and specificity of 80.0% and 83.3%, respectively, and an area under the curve of 0.83.

Study limitations included a relatively small sample size, retrospective design, and the use of various PET scanners on different patients, potentially leading to variation in standardized uptake value measurements.

Whereas PET-CT abnormalities are common in lungs, lymph nodes, and glands among patients with and without lymphoma, it appears that the highlighted combination may help differentiate the 2 groups, identifying possibly evolving lymphoma in individuals with pulmonary nodules and parotid maximum standardized uptake value ≥4.7.

Reference

Keraen J, Blanc E, Besson FL, et al. Usefulness of 18F-FDG positron emission tomography (PET) for the diagnosis of lymphoma in primary Sjögren’s syndrome [published online January 7, 2019]. Arthritis Rheumatol. doi:10.1002/art.40829