Hypoxic Imaging With ^99mTc-HL91 And Its Correlation With HIF-1α In NPC

Objective:To study the correlation of 99rnTc-HL91 imaging with HIF-1αexpression for nasopharyngeal carcinoma (NPC).Methods:12 inpatients with pathologically proven NPCs were enrolled into the study before chemotherapy and radiotherapy. Local planar scans and SPECT acquisitions were performed at 1 and 4 hour after intravenous injection of 740-1110 MBq (20-30 mCi) 99mTc HL91. Regions of interest (ROIs) were drawn around the tumor on planar and tomographic 99mTc-HL91 images. The tumor (T) to normal tissue (N) values (T/N) was counted. Slices of the highest nuclide accumulation sites of the nasopharyngeal tumors and the cervical node metastases were counted as the tumor (T) values. Normal tissue background regions (N) were taken from qualitatively normal regions on the opposite side of the body. The same T/N values were drawn on the planar images. The expression of HIF-1αwas determined by immunohistochemistry.Results:(1)Tumor activity is more easily identified at 4 hr rather than at 1 hr postinjection mainly due to a reduction in background activity(P<0.01). (2)T/N ratios are consistently much higher with 99mTc-HL91 SPECT images than planar images (P<0.01) in this study. (3)Accumulation activity at the nasopharyngeal tumor sites was identified in all patients on planar images and most prominently identified by SPECT slices. But most of the cervical node metastases couldn't be clearly observed on the planar images though they're very prominent accumulation on the SPECT slices. (4) There are two cases showing that the accumulation of the tracer at the nasopharyngeal tumor sites isn't correlated with the cervical node metastases. While the cervical node metastases showed massive tracer accumulation, the nasopharyngeal tumor sites showed few tracer accumulations. The contrary condition exists. (5) The accumulation of the tracer at the nasopharyngeal tumor sites has no statistical difference with the cervical node metastases. (6)There's one case showing that cyst in the tumor couldn't accumulate the tracer. (7) HIF-1αexpression(39.8%～77.8%, mean: 56.38%) was better correlated with the uptake of HL91 at the nasopharyngeal tumor sites on SPECT slices while it wasn't correlated with the uptake of HL91 of the nasopharyngeal tumor sites on planar images and the uptake of HL91 of the metastatic cervical nodes. This means the planar images couldn't be the proof to diagnose hypoxic situation of the nasopharyngeal tumors.Conclusion:99mTc-HL91 imaging afforded good images to demonstrate the uptake of the tracer at the nasopharyngeal tumor sites and the cervical node metastases. The uptake of HL91 at the nasopharyngeal tumor sites on SPECT slices was better correlated with HIF-1αexpression. Both meant hypoxia existed in NPCs.