Biokinetics of indium-111 labeled platelets after cryotherapy of hepatic metastases

Full text: The present investigation was performed to evaluate mean platelet live-span and the proportion of platelet disposal in different organs in patients after hepatic cryotherapy. Seven patients with advanced colorectal cancer and liver metastases were included. Directly before the surgical procedure a blood specimen was drawn and an in vitro labeling of patients platelets with 18 MBq Indium-111 oxime was performed. Reinjection was done intraoperatively just before cryotherapy. Blood specimen were drawn at 1, 2, 3, 24 und 48 h p.i.. Whole-body scintigraphy was acquired on day two alter operation. The evaluation comprised the calculation of mean platelet live-span and of organ activities as percentage of whole-body activity. The local disposal of platelets at the site of cryotherapy ranged from 0 to 35.2 percent, the mean value was 16,2 ± 12,2 percent (mean ± SD). The mean half-time of time-activity curve gave 0.6 to 2.4 days (mean ± SD: 1.6 ± 0.6 d; normal value: 3.5-6 d), the mean platelet life-span was between 2.1 and 5.2 days corresponding to a mean value of 3.4 ± 1.0 days (normal value: 7-11 d). The evaluation of SPECT slices of large liver metastases demonstrated that platelet disposal takes place at the border zone of the metastases just around the necrotic center. We conclude that the enhanced local platelet trapping is a major cause for cryothermia-induced systemic thrombocytopenia. (author)