99MTc-MIBI spect in detection of primary nasopharyngeal carcinoma and differentiation of residual or recurrent lesions after radiotherapy

Objective: To investigate the diagnostic potential of 99mTc-sestamibi (MIBI) SPECT in evaluating the extent of primary disease and differentiating residual/recurrent lesions post- radiotherapy in patients with nasopharyngeal carcinoma(NPC). Methods: Twenty patients with primary NPC histologically confirmed with biopsy underwent repeated 99mTc-MIBI SPECT before radiotherapy and at 3 months, 6 months after radiotherapy. The scintigraphy were compared with that of CT/MRI. Nasopharyngeal-to-scalp ratios were obtained as MIBI uptake index (MUI). The recurrent lesions were judged with biopsy and/or clinical follow-up which lasted for 18 months post radiotherapy. Receiver operating characteristic analysis was used to defined the cutoff of MUI. Results: When MUI 2.15 was used as cutoff, the sensitivity ,specificity and accuracy for detecting the primary NPC were all 95%. The optimum cutoff 1.32 of MUI was defined with a sensitivity of 75%, a specificity of 93.8%, and an accuracy of 90% for differentiating residual/recurrent lesions from the benign process post- radiotherapy, while CT/MRI evaluations showed sensitivity of 75%, specificity of 81.3%, and accuracy of 80%. Combination CT/MRI and 99mTc-MIBI SPECT for 16 NPC patients with congruent results showed a sensitivity of 100%, a specificity of 92.1%, and an accuracy of 93.8% for differentiating residual/recurrent NPC from benign lesions. Conclusions: 99mTc-MIBI SPECT may play a role in detecting primary NPC. The combination of CT/MRI and 99mTc-MIBI SPECT may give more accurate diagnosis and diferentiation in distinguishing residual/recurrent lesions in the follow-up post-radiotherapy. (authors)