Biometabolic distribution of 99mTc-3PRGD2 and its potential value in monitoring chemotherapeutic effects

Objectives 99mTc-3PRGD2 is a novel radiotracer that can detect integrin αvβ3. We investigated the biometabolic distribution characteristics of 99mTc-3PRGD2 and its potential value for monitoring chemotherapeutic effects.

Methods VX2 squamous cell tumors were implanted into 18 rabbits, which were randomized into a treatment and control group. 99mTc-3PRGD2 scintigraphy was performed prior to cisplatin injection and repeated on days 0, 1, 7 and 14 post-injection. The images were compared between the two groups. Continuous dynamic scanning, static scanning and SPECT/CT were performed over 3 h. The peak time (time to reach peak) and tumor-to-normal (T/N) ratios were calculated. Autoradiography was performed on excised tumors from three rabbits/ group on day 1.

Results The half-life of the radiotracer in the heart, liver and tumor of rabbits in the control group were 3.43±0.94, 13.41±9.17 and 70.83±33.37 minutes respectively. In the treatment group, tumor size was significantly reduced on day 7 (P < 0.05). The peak time delayed immediately after cisplatin administration on day 0 and on day 1 in the treatment group while it shortened in the control group. The T/N ratios at 3 h decreased in the treatment group while they increased in the control group(P < 0.05). The visibility of the images was fainter for the treatment group compared to the control group on autoradiographic images. More necrosis districts were seen on the scintigraphic images and H&E staining for the treatment group throughout treatment.

Conclusions The delayed peak time of the dynamic phase and the decreased T/N ratios at static 3 h suggest that 99mTc-3PRGD2 scintigraphy may potentially be employed to monitor the chemotherapeutic effects of drugs. The effective half life of the tracer in the tumor could be referential for other studies and further clinical works.