Radiation-absorbed dose estimates to normal organs following intraperitoneal 186Re-labeled monoclonal antibody: methods and results.

The radiation-absorbed dose was estimated following i.p. administration of a 186Re-labeled murine antibody, NR-LU-10, in 27 patients with advanced ovarian cancer. Data for the dosimetry estimation were obtained from quantitative gamma camera imaging and gamma counting of serum and i.p. fluid radioactivity. A peritoneal cavity model was used to estimate the dose to normal organs from radioactivity within the peritoneal cavity. Estimates of radiation-absorbed dose to normal organs in rad/mCi administered (mean + SD) were: whole body, 0.7 + 0.3; marrow, 0.4 + 0.1; liver, 1.9 + 0.9; kidneys, 0.2 + 0.2, and intestine, 0.2 + 0.2. The radiation-absorbed dose estimates to the normal peritoneal surface varied depending on the volume of fluid infused and whether the activity was measured by the gamma camera or from the peritoneal fluid samples. Using gamma camera data, the peritoneal surface dose ranged from 7 to 36 rads/mCi; when using the peritoneal fluid sample data, the dose ranged from 2 to 25 rads/mCi. Myelosuppression, observed in several patients, correlated best with marrow dose estimates based on the serum radioactivity, and significant toxicity was observed at marrow doses greater than 100 rads. The noninvasive methods of dose estimation for i.p. administration of radioimmunoconjugates provided reasonable absorbed dose estimates when compared with previously described, more invasive methods.