Abstract: Background and purpose: Neoadjuvant chemotherapy with docetaxel was gaining more attention in the treatment for locoregionally advanced nasopharyngeal carcinoma (NPC). The prediction of the sensitivity to neoadjuvant chemotherapy with docetaxel could enable clinicians to individualize treatment protocols for NPC. Recently we found that ^99mTc-MIBI imaging in NPC could predict tumor response to chemotherapy with cisplatin plus 5-FU. However, there was no study to support similar findings in NPC patients receiving chemotherapy containing docetaxel. This study was to evaluate the value of double-phase ^99mTc-MIBI SPECT/CT in predicting response to neoadjuvant chemotherapy with docetaxel-based regimen for nasopharyngeal carcinoma. Methods: Thirty-one nasopharyngeal carcinoma patients participated in this prospective study. Before treatment, early and delayed singlephoton emission computed tomography/compute tomography (SPECT/CT) images were obtained instantly and 2 hours after an intravenous injection of 25-30 mCi ^99mTc-MIBI. All patients received neoadjuvant chemotherapy consisting of docetaxel, cisplatin plus 5-FU for two cycles. The relationships between efficacy of neoadjuvant chemotherapy and the early uptake ratio, late uptake ratio and washout rate of ^99mTc-MIBI were evaluated. Results: According to the MRI, the early uptake of ^99mTc-MIBI (2.67±0.83) in the lesions which were sensitive to chemotherapy was significantly higher compared with that (1.69±0.46) in the insensitive lesions(P=0.003). The difference of the late uptake between the sensitive(1.46±0.39) and the insensitive (1.06±0.62) was also statistically significant (P=0.026). However, the washout rate of ^99mTc-MIBI was not significantly different between the two groups (P=0.23). Through ROC curve analysis, the AUC for early uptake of ^99mTc-MIBI and late uptake were 0.84. The sensitivity, specificity, positive predictive value and negative predictive value were 74.2%, 87.5%, 95.8% and 46.7% for early uptake when the cut off value of 1.97 was used. Conclusion: The uptake of 99mTc-MIBI in both early phase and late phase could predict the efficacy of neoadjuvant chemotherapy with docetaxel-based regimen.

Key words: Nasopharyngeal carcinoma, ^99mTc-MIBI SPECT/CT, Neoadjuvant chemotherapy, Multidrug Resistance