title: Monitoring of 57Co-bleomycin delivery to brain metastases and their tumors of origin.
abstract: The concentration of cobalt-57 (57Co)-labeled bleomycin delivered to three brain metastases and to their tumors of origin in the lungs was measured using a single-photon emission computerized tomography technique. In two brain metastases the 57Co-bleomycin concentration measured at different times after the intravenous injection was significantly lower than that in the originating lung tumors (p less than 0.01 and p less than 0.001). In these two patients, the tumor cumulative concentration (TCC) of drug in the brain neoplasm compared to the lung carcinoma was 12.92 versus 15.12 and 10.30 versus 19.74 micrograms/cc/min. In the third patient there was no significant difference in drug concentration between the tumor in the brain and in the lung (TCC 16.02 vs. 15.09 micrograms/cc/min). There was a significant difference in the drug TCC between the three brain metastases: the difference between the lowest and highest concentrations was more than 50% (10.3 vs. 16.02 micrograms/cc/min). When the concentration in the tumor over time (CT(t)) of the 57Co-bleomycin was compared in the brain and lung tumors, a good correlation was found in each of the three cases (r = 0.93, 0.99, and 0.97). This suggests that the difference in drug uptake between brain metastases and their originating lung tumor is a quantitative rather than a qualitative phenomenon. The results show that the amount of drug to which brain metastases are exposed varies and may be very low in some tumors; therefore, effectiveness of drug delivery may play a role in the nonresponsiveness of brain metastases to treatment.
mesh_terms: D001761:Bleomycin / Q000493:pharmacokinetics*; D001932:Brain Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism* / Q000556:secondary; D003037:Cobalt Radioisotopes; D006801:Humans; D008175:Lung Neoplasms / Q000000981:diagnostic imaging / Q000378:metabolism*; D014055:Tomography, Emission-Computed
chemical_list: D003037:Cobalt Radioisotopes; D001761:Bleomycin