Clinical usefulness of FDG PET/CT in patients with Castleman disease

1681 Objectives: Castleman disease (CD) is an uncommon, poorly understood lymphoproliferative disorder with varying clinical manifestations. We aimed to compare the FDG PET/CT and clinical findings and assess the prognostic value of FDG PET/CT in patients with CD. Methods: We retrospectively reviewed FDG PET/CT images of patients with histologically confirmed, treatment naive CD. FDG uptake of the involved lymph node (LN) was visually classified as positive or negative. The extent of the involved LN was categorized as limited (on the same side of the diaphragm) or extensive (on both sides of the diaphragm) as for lymphoma staging. Sites of extranodal involvement were also noted. The association between FDG PET/CT and clinical findings (clinical symptoms, histologic subtype, and laboratory findings) was assessed and estimate of survival function for overall survival (OS) was compared by log-rank test. Results: In total, 57 patients (42 men, 15 women; median age 50 years, range 26-82 years) were included. Of these patients, 10 (18%) had unicentric CD and 47 (82%) had multicentric CD. By histologic classification, 28 patients (49%) had hyaline vascular subtype; 23 (40%) had plasma cell subtype; and 6 (11%) had mixed or unclassified subtype. At the time of the FDG PET/CT imaging, 17 patients (30%) had clinical symptoms and 35 (61%) had abnormal laboratory findings (low hemoglobin, low platelet, low albumin, or elevated high-sensitivity C-reactive protein levels). In FDG PET/CT assessments, 44 (77%) had LNs with FDG uptake greater than the liver. Twenty-seven patients (47%) had limited nodal involvement and 30 (53%) had extensive nodal involvement. Extranodal involvement was suspected in 25 patients (44%). Of the 57 patients, the patients presented with both extensive nodal involvement on FDG PET/CT and clinical symptoms in 12 (21%) and the patients presented with both extensive nodal involvement on FDG PET/CT and abnormal laboratory findings in 22 (39%). Eleven patients (19%) died during the follow-up period (median follow-up time 31 months). One patient among the 11 deaths had limited nodal involvement on baseline FDG PET/CT and OS of 134 months. The estimated 5 years OS was 100% for the patients with limited nodal involvement and 67% for the patients with extensive nodal involvement (p=0.031). Conclusion: FDG PET/CT is useful for assessing the extent of disease involvement in patients with CD, which may be associated with survival.