Octreotide Directly Labeled With ～(99m)Tc And Preliminary Imaging On Small Cell Lung Cancer

Objective : To develop an optimal method to label Octreotide with 99mTc directly and evaluate its significance as an imaging agent of somatostatin receptor positive tumors for small cell lung cancer. Methods: 1 Sodium ascorbate and Na2S2O4 were adopted to label Octreotide with Tc. The mixture was purified by using a Sep-Pak CIS reversed-phase extraction cartridge. The radiochemical purity was measured by High Pressure Liquid Chromatography (HPLC) and biolayer chromatography combining method of silver stain. 2 99mTc-Octreotide was injected through the ear vein in 15 normal rabbits to study the character of its radioactivity biodistribution and metabolism. (3) The somatostatin-receptor positive imaging procedure using 99mTc-Octreotide was reported in 5 patients with histologically proven small cell lung cancer and compared with CT findings. Results: 1 The yield of 99mTc-Octreotide was 71.87%±1.12% measured by biolayer chromatography combining silver stain whereas 71. 37%±1.83% by HPLC. There was no statistic significance between them. (P>0. 05). Radiochemical purity was 95.62%± 1. 78%, 94. 78%± 1. 56%(P>0.05) respectively measured by the two methods above after purification. The compound remained stable with no precipitation and its radiochemical purity was 92. 1% ?93.6% after 4 hour at room temperature. (2) In rabbits, 99mTc-Octreotide injected intravenously was rapidly cleared from the circulation mainly by the renal , secondly through the hepatobilinary into intestinal tract and with very little normal organ uptake. Time-activity curve of heart was highest with time to peak 60s, time to 1/2 peak398±4. 6s. Renal curve decreased slowly with Time to peak 374±5. 6s and crossed with heart curveat 274s. Liver curve was lower and decreased slowly with time to peak 50s. (3) In 3 of 5 patients with small cell lung cancer showed primary diseases of intense uptake, 1 low uptake, 1 no uptake, whereas only 3 of 5 patients showed positive findings by CT exam. The ratio of tumor and normality (T/N) was no significantly different among 0.5h, 1h, 2h, 3h (1.52 ± 0.31, 1.72±0.42, 1.91±0.55, 1.88±0.38 , F=2.125, P>0.05). Conclusions: These results suggested that Octreotide labeled with 99mTc was feasible. Imaging with this radiopharmacentical to detect small cell lung cancer and its local or extent metastases was a noninvasive exam technique. 99mTc-Octreotide was a promising radiopharmacentical for scintigraphic imaging of tumors rich in somatostatin receptors.Postgraduate: Wang xufu Directed by: Professor Zuo shuyao...