Radioisotope-guided surgery in patients with pheochromocytoma and recurrent medullary thyroid carcinoma: a comparison of preoperative and intraoperative tumor localization with histopathologic findings.

BACKGROUND. The objective of this study was to appraise the detection of metastases of medullary thyroid carcinoma (MTC) and pheochromocytoma using radioguided surgery (RGS) and to compare the results with external imaging modalities, surgical palpation, and histopathologic findings. METHODS. Twenty-five patients with recurrent MTC underwent preoperative scintigraphic imaging with 500 megabecquerels (MBq) of technetium 99m(V)-dimer-captosuccinic acid [ 99m Tc(V)-DMSA] and 222 MBq of indium 111 ( 111 In)-pentet-reotide. The radiopharmaceutical that showed the greatest preoperative tumor uptake was selected for intraoperative RGS. Surgery was performed 24 hours after the administration of 111 In-pentetreotide or 4 hours after the injection of 99m Tc(V)-DMSA. Furthermore, three male patients underwent surgery who suffered from recurrent pheochromocytoma (injection of 180 MBq iodine 123-labeled metaio-dobenzylguanidine [ 123 I-MIBG] 4-5 hours before surgery). RESULTS. Overall, lesion detection sensitivities in patients with MTC for computed tomography, 111 In-pentetreotide, and 99m Tc(V)-DMSA were 32%, 34%, and 65%, respectively. Surgical palpation identified lymph node metastases of recurrent MTC with a sensitivity of 65%, whereas RGS localized 64 malignant lesions (sensitivity, 97%). Altogether, 71 lesions could be excised, 5 of which were adjudged false positive with respect to MTC metastases. Both surgical palpation and RGS localized all paravertebral subdiaphragmatic lesions (size ≥ 2 cm) of recurrent pheochromocytoma seen in the preoperative MIBG scan. CONCLUSIONS. RGS was capable of localizing more and smaller metastases of MTC compared with conventional imaging modalities and surgical palpation. However, the relatively high radioligand accumulation in the kidneys ( 111 In-pentetreotide) and the dense hepatic and biliary signals using MIBG limited their use for intraoperative detection of tumors in the area of the adrenal gland.