A cost-efficient diagnostic imaging algorithm incorporating I-123 MIBG SPECT/CT for suspected pheochromocytoma

Objectives To develop a cost-efficient diagnostic imaging algorithm incorporating I-123 MIBG SPECT/CT for clinically suspected pheochromocytoma.

Methods A retrospective review of I-123 MIBG SPECT/CTs performed at our institution between Jan 2007 and Feb 2011 for clinically suspected pheochromocytoma was performed. SPECT/CT findings, 24 hour fractionated urine metanephrine (FUM) measurements (within 2 months of SPECT/CT), and relevant CT and/or MR findings (within 6 months of the SPECT/CT) were recorded. A cost-efficient diagnostic imaging algorithm was developed, maintaining diagnostic accuracy. Actual imaging costs for this cohort were compared with the expected costs using the algorithm.

Results 71 patients were included. If the FUM were normal, all of the SPECT/CT studies were negative (16/71). Conversely, 87% of patients with a total metanephrine (TM) ≥1.7µmol/24hr (15/71) had a positive SPECT/CT study. If the TM was <1.7µmol/24 hr but one or more of the metanephrine fractions were abnormal (40/71), only 39-58% of the SPECT/CT studies were positive. Of these, none had a positive SPECT/CT if they had a negative or benign CT and/or MR (14/71). An average of $3273.85/patient was spent on imaging (76 SPECT/CT scans, 44 CT scans, and 25 MRI studies). By using the developed algorithm, the average cost could be lowered to $1897.94/patient (31 MIBG, 20 CT, 20 MRI).

Conclusions Patients with clinically suspected pheochromocytoma should initially be evaluated with 24 hour FUM. If the TM is ≥1.7µmol/24hr, then the patient should be evaluated with an I-123 MIBG SPECT/CT. If the FUM are all normal then no further imaging is indicated. A CT or MR study should be performed if the TM is <1.7µmol/24hr but one or more of the metanephrine fractions is abnormal. If the CT or MR is normal or benign, no further imaging is required. If abnormal, further evaluation with an I-123 MIBG SPECT/CT is indicated. Using the algorithm would result in a cost-savings of 58% ($1375.91/patient) with no expected change in accuracy