Hypoxic Imaging with ^99mTc-HL91 and its Correlation with HIF-1α in NPC

Objectives To study the correlation of ^99mTc-HL91 imaging with HIF-1α expression 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 ^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) were counted. The expression of HIF-1α was determined by immunohistochemistry.

Results Tumor activity was more easily identified at 4 hr rather than at 1 hr post-injection mainly due to a reduction in background activity (P<0.01). Accumulation activity at the nasopharyngeal tumor sites was identified in all patients on planar images and SPECT slices. Most of the cervical node metastases couldn’t be clearly observed on the planar images though they showed prominent accumulation on the SPECT slices. Two cases showed that the accumulation of the tracer at the nasopharyngeal tumor sites wasn't correlated with the cervical node metastases. The accumulation of the tracer at the nasopharyngeal tumor sites had no statistical difference with the cervical node metastases. HIF-1α expression(39.8%～77.8%, mean: 56.38%) was better correlated with the uptake of HL91 at the nasopharyngeal tumor sites on SPECT slices (P<0.05).

Conclusions ^99mTc-HL91 imaging afforded good images 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-1α expression.