(18)F-fluorodeoxyglucose position emission tomography (FDG-PET) for monitoring disease activity and treatment response in idiopathic retroperitoneal fibrosis.

OBJECTIVE: To evaluate the value of (18)F-fluorodeoxyglucose positron emission tomography (FDG-PET) in monitoring disease activity and predicting treatment response in idiopathic retroperitoneal fibrosis (iRPF). PATIENTS AND METHODS: This prospective study was approved by the institutional review board. Informed consent was obtained from all patients. Twenty-six patients with iRPF receiving tamoxifen monotherapy underwent repeated FDG-PET (baseline and, if positive, at 3 months) and computed tomographic (CT) scanning (baseline, 4 and 8 months). Maximal RPF mass thickness in 3 different view directions was measured on each CT scan; FDG-uptake was semi-quantified using a visual 4-point scale. Initial and follow-up PET scan results were correlated with clinical, laboratory and CT scan follow-up data. Treatment outcome was the aggregate measure of clinical, laboratory and CT-documented response to tamoxifen. RESULTS: FDG-PET was positive in 20 patients. Patients with positive PET scan result had higher C-reactive protein level (P=0.02) and larger mass size (P=0.01) compared with patients with negative PET scan result. Visual PET score correlated with C-reactive protein level (P=0.002) and CT-documented mass thickness (P=0.04). Visual PET score decreased following treatment (P<0.01). This decrease correlated with decrease in ESR (P<0.001) but not with CT-documented mass regression. Positive predicting value (PPV) of initial positive PET scan result was 0.63; PPV of negative follow-up PET scan result in patients with initial positive PET scan result was 0.66. CONCLUSION: FDG-PET is valuable in detecting (recurrent) disease activity. Short-term follow-up with FDG-PET cannot be routinely recommended for the therapeutic evaluation of RPF disease in tamoxifen-treated patients.

Clinical value of gallium-67 SPECT scintigraphy in the diagnostic and therapeutic evaluation of retroperitoneal fibrosis: a prospective study.

BACKGROUND: Gallium-67 (67Ga) scintigraphy may be useful in evaluating patients with retroperitoneal fibrosis (RPF), but a systematic assessment of its value is lacking. OBJECTIVE: Prospective evaluation of the value of 67Ga scintigraphy in assessing active RPF disease and in predicting treatment response. METHODS: Thirty-four patients with nonmalignant RPF treated with tamoxifen underwent 67Ga scintigraphy at baseline and--if baseline gallium scan was positive--at 3 months follow-up. Gallium scans were visually scored according to pathologic 67Ga-uptake compared to normal bone marrow 67Ga-uptake. Results were correlated with other (follow-up) measurements. Value of (follow-up) 67Ga scintigraphy in predicting treatment response was also assessed. RESULTS: Gallium scans were positive in 24 patients (71%). Mass thickness was greater in patients with positive gallium scan compared with patients with negative gallium scan (P = 0.006). Visual gallium score correlated with mass thickness (P = 0.006). Visual gallium score decreased significantly following tamoxifen treatment (P < 0.0001). Decrease in visual gallium score correlated with decreases in C-reactive protein and erythrocyte sedimentation rate (P = 0.019) and with decrease in mass thickness (P < 0.01). Positive predicting value (PPV) of positive baseline gallium scan was 0.71; PPV of negative follow-up gallium scan in patients with initial positive scan was 0.89. 67Ga scintigraphy detected extra-abdominal involvement in one patient and recurrent active disease in two symptomatic patients with normal acute-phase reactants and stable residual mass. CONCLUSION: 67Ga scintigraphy is useful in assessing (recurrent) activity of RPF disease and in evaluating treatment response in patients with initial positive gallium scan.