The influence of irradiation on the biological half-life of prostacyclin in plasma of patients with gastrointestinal cancer.

In seven patients suffering from inoperable pancreatic cancer and in 14 patients with inoperable colonic cancer the half-life (T/2) of prostaglandin (PG)I2 in plasma in vitro has been determined before and at various intervals after irradiation. No significant difference of PGI2-T/2 could be observed either before irradiation, at the end of the irradiation period or 3 and 6 weeks after the last irradiation. Thus irradiation does not appear to interfere with the degradation of PGI2-T/2 in plasma. In patients with inoperable pancreatic and colonic cancer the PGI2-T/2 was not significantly different to that of the PGI2-T/2 of controls. Thus, a shortening of PGI2-T/2 is not a common feature in tumour patients. Hyperaggregation promoting seeding of metastases is not influenced by irradiation via the particular parameter of the PG-system.