Purpose
To study the utility of combined positron emission tomography/computed tomography (PET/CT) in the staging and management of ocular adnexal lymphoma (OAL).
Methods
A retrospective review of all patients diagnosed with OAL between January 2004 and April 2013 was performed. Patients were included if they were diagnosed with an OAL with orbital involvement confirmed by immunohistopathology and/or flow cytometry and underwent head and body PET/CT prior to the institution of therapy. Data analyzed included patient demographics, OAL diagnosis based on the World Health Organization’s reclassification of lymphoma, results of systemic staging by PET/CT, and type of therapy. Standard uptake values (SUVs) on PET/CT were also analyzed. SUVs in the ocular adnexa were analyzed separately from those in the body. Data was also analyzed after reclassifying specific lymphoma subtypes into either “indolent” or “aggressive” categories, based on known clinical behavior of each lymphoma subtype. Descriptive statistics and analysis (Fisher exact test and Wilcox sum rank test) for correlations were carried out with SPSS 16.0.1.
Results
Forty-one patients met the inclusion criteria. Analysis of SUVs showed a statistically significant difference in orbital SUVs between indolent and aggressive lymphoma subtypes (p=0.003). However, no significant difference was noted when comparing body SUVs (p=0.2225). Comparison of the distribution of lymphoma subtypes across initial stages with PET alone was compared to published reports on staging distributions utilizing additional modalities (CT, MRI, bone marrow biopsy), and no statistically significant difference was found. Of note, although 12 of 27 (44%) indolent OAL were stage I compared to only 2 of 14 (14%) aggressive OAL, this difference was not statistically significant (p=0.1928).
Conclusions
The orbital SUV of indolent OAL is significantly lower than of aggressive OAL, but no difference was noted in body SUVs. PET appears to upstage indolent OAL when compared to previous studies, but this finding must be tempered by known limitations of PET in orbital disease and in non-Hodgkin lymphoma (NHL), including resolution, background metabolic activity of the brain, and variable tracer uptake in indolent NHL. Based on this limited initial study, the utility of PET/CT in the staging of indolent lymphoma subtypes remains unproven.