Tc-99m-3P(4)-RGD(2) radiotracers for SPECT/CT of esophageal tumor

In recent years, several RGD (Arg-Gly-Asp)-based radiotracers have already been successfully tested in human for the visualization of integrin alpha v beta 3, demonstrating its feasibility in tumor diagnosis. In this paper, we evaluated the Tc-99m-3P(4)-RGD(2) single photon emission computed tomography/computerized tomography (SPECT/CT) in patients suffering from space occupying disease of esophagus. 40 patients (34 males and 6 female; mean age: 58.3 years) with a suspected space occupying lesion of esophagus were included, thus finally obtaining their definite pathologic diagnosis (malignant, n=32; benign, n=8). All patients underwent endoscopic, barium esophagography and SPECT/CT imaging preoperatively. The chest SPECT was performed at 4 h after administration of Tc-99m-3P(4)-RGD(2) with a dose of 939 +/- 118 MBq. The diagnosis precision, sensitivity and specificity among these methods were compared. The relationship between radioactive uptake and clinical pathological stage of esophageal carcinoma was discussed by calculating the tumor to normal esophagus (T/N). Meanwhile, the integrin alpha v beta 3 expression was assessed immunohistochemically in postoperative esophageal tissues. 31 patients were diagnosed as esophageal carcinoma; and 1, leiomyosarcoma; and 6. leimyoma; and 2, esophageal tuberculosis. The accuracy, sensitivity and specificity of barium esophagography, endoscopic and SPECT/CT imaging are 92.5/93.8/87.5%, 97.5/96.9/100%, and 90/90.6/87.5%, respectively. Abnormal accumulation of radiotracer in 29 malignant lesions is observed. The SPECT/CT imaging displayed the region of radioactive uptake and lesions matched extremely with the TIN ratio from 1.31 to 2.79 (mean 2.04). A case with pulmonary metastases and a case with mediastinal lymph node metastases were found which were missed by barium esophagography and endoscopic. The Tc-99m-3P(4)-RGD(2) uptake of the esophageal carcinoma masses had no relevance to the tumor pathologic classification (P>0.05). There was a significant positive correlation between T/N ratio and positive cell percentage of integrin alpha v beta 3 (r=0.976), demonstrating the certain clinical potential in the diagnosis of esophageal carcinoma.