Pilot Study Of^99mTc-MIBI SPECT/CT In Predicting The Response Of Neoadjuvant Chemotherapy With Docetaxel-based Regimen For Locoregionally Advanced Nasopharyngeal Carcinoma

Background:Neoadjuvant chemotherapy with docetaxel-based regimen has shown great promise for the treatment of locoregionally advanced nasopharyngeal carcinoma (NPC). However for patients with chemotherapy-resistant NPC, neoadjuvant chemotherapy may cause a delay of definitive radiotherapy and unnecessary toxicities. If patients with chemotherapy-resistant NPC were screened out before treatment, then they would be spared from ineffective induction chemotherapy.99mTc-MIBI SPECT/CT has been reported to predict the efficacy of chemotherapy in lung cancer, breast cancer and lymphoma. In our previous study, we have shown that "Tc-MIBI SPECT/CT can predict response to induction chemotherapy with cisplatin and5-Fu in NPC. However, its role in predicting response to docetaxel-based regimen had not been defined. Therefore, a prospective study is carried out to evaluate the role of99mTc-MIBI SPECT/CT in assessing the response of nasopharyngeal carcinoma to neoadjuvant chemotherapy with docetaxel, cisplatin and5-Fu.Objective:To approach double-phase99mTc-MIBI SPECT/CT in predicting the response of nasopharyngeal carcinoma to neoadjuvant chemotherapy with docetaxel-based regimen.Methods:Thirty-one pathologically proven nasopharyngeal carcinoma patients participated in this prospective study. Before treatment, early and delayed single-photon emission computed tomography/compute tomopraphy (SPECT/CT) images were obtained instantly and2hours after an intravenous injection of25-30mCi99mTc-MIBI. All the patients received neoadjuvant chemotherapy consisting of docetaxel (60mg/m2/d on day1), cisplatin (25mg/m2/d on days1-3) plus5-FU (500mg/m2/d on days1-5) for two cycles. The efficacy of neoadjuvant chemotherapy was evaluated by magnetic resonance imaging performed one week after the second cycle chemotherapy. The relationships between efficacy of neoadjuvant chemotherapy and the early uptake ratio, late uptake ratio and washout rate of99mTc-MIBI were evaluated. Receiver operating characteristic curve (ROC curve) was drawn to determine the cutoff value of the diagnostic test.Results:According to the MRI, among twenty primary lesions in the nasopharynx, two achieved complete remission (CR),14had partial response (PR),4experienced stable disease, none of patients had progressive disease (PD). Thus16lesions were sensitive to chemotherapy and4insensitive. There were19lesions in neck. One had CR,14had PR, four experienced SD, no lesion progressed. Thus15lesions were sensitive to chemotherapy and4insensitive. The difference of the response rate between nasopharyngeal lesions and cervical lesions was not statistically significant. The early uptake of99mTc-MIBI (2.67±0.83) in the lesions which were sensitive to chemotherapy was significantly higher (p=0.003) compared with that (1.69±0.46) in the insensitive lesions. 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 of99mTc-MIBI was not significantly different between the two groups. Through ROC curve analysis, the AUC for early uptake of99mTc-MIBI and late uptake were0.84(SE:0.064;95%CI:0.715-0.967, p=0.003) and0.752(SE:0.118;95%CI:0.521-0.983, p=0.03). The sensitivity, specificity, positive predictive value and negative predictive value were74.2%,87.5%,95.8%and46.7%for early uptake and87.1%,62.5%,90%and66.6%for late uptake, respectively.Conlusions:The uptake of99mTc-MIBI in both early phase and late phase could predict the efficacy of neoadjuvant chemotherapy with docetaxel-based regimen.