Combined positron emission tomography/computed tomography for diagnosis and monitoring of orbital adnexal lymphoma.

PURPOSE: Combined whole-body F-18-fluoro-2-deoxyglucose positron emission tomography / computed tomography ([18F]FDG-PET/CT) gives precise information about tumour morphology and metabolism. The standardized uptake value (SUV) allows quantification of tumour metabolism. The diagnostic value of PET/CT in patients with suspected orbital adnexal lymphoma (OAL) was evaluated.

METHODS

Of 21 patients with suspected OAL who underwent combined whole-body PET/CT between 07/2002 and 11/2016, 16 were scanned before and five after orbital biopsy. Histological tumour determination was performed in all cases via biopsy. Correlation between SUVmax and therapeutic status, lymphoma stage (Ann Arbor classification) and histological grading was tested.

RESULTS

All lesions could be depicted by combined whole-body PET/CT. Histology confirmed two malignant T-cell and 18 malignant B cell non-Hodgkin lymphomas as well as one patient suffering from systemic lymphoma with chronic polypoid sinusitis. SUVmax levels of orbital findings were significantly lower after therapy (p < 0.001; Fisher's exact test). Higher stage lymphomas (Ann Arbor classification) expressed significantly higher SUVmax levels (p = 0.014; Fisher's exact test). There was no significant correlation of SUVmax values and histologic grading in this patient collective.

CONCLUSION

Positron emission tomography/computed tomography (PET/CT) depicted vital tumour metabolism of OALs accurately. In cases scanned after orbital biopsy and under systemic therapy, no elevated tumour metabolic activity was expressed. This underlines the reasonable application of PET/CT for therapy monitoring besides whole-body staging. Higher-stage OALs show higher metabolic activity. Yet, for adequate therapy initiation, histology remains indispensable.