PHARMACOKINETICS AND RADIATION-DOSE OF Y-90 CITRATE AND Y-90 EDTMP MEASURED WITH Y-86 AND PET

Painful bone metastases are palliatively treated with {beta}=emitting isotopes such as Y-90. To obtain quantitative biokinetic data of Y-90-citrate and Y-90-EDTMP (ethylenediaminetetramethylenephosphonate) the {beta}{sup +}-emitting sister isotope Y-86 (T{sub 1/2}=14.7 h, 33% {beta}{sup +}) was prepared and applied as Y-86-citrate and Y-86-EDTMP using whole-body PET measurements. Patients with multiple bone metastases of prostate cancer received about 200 MBq Y-86-citrate (n=4) or Y-86-EDTW (n=3). Dynamic scans were recorded over the liver up to 4 h after injection (p.i.) followed by 3 to 5 quantitative whole-body PET scans from 4 to 72 h p.i. The reconstructed transversal PET images were evaluated to obtain time-activity curves in normal bone, metastases and liver. Based on these Y-86-uptake kinetics data the radiation doses caused by the Y-90-compounds were calculated. Whereas Y-86-citrate was found in the liver (14% at 4 h p.i.), this organ was not visible after the injection of Y-86-EDTMP. For both compounds 20% to 40% of the injected activity was found in the skeleton. Maximum ratios of activity concentration of metastasis to normal bone reached 9:1 for citrate and 15:1 for EDTMP. The dose to the red marrow was 2.6{plus_minus}0.4 mGy per 1 MBq of injected Y-90-citrate and 1.7{plus_minus}0.3 mGy for Y-90-EDTMP. Themore » doses delivered to the metastases varied from 9 to 39 mGy per 1 MBq of the injected Y-90-activity. This study shows that Y-86 and PET allow to compare the pharmo-kinetics of different Y-90-radiotherapeuticals quantitatively and to derive dosimetric data for the individual patient. Furthermore, because of the chemical similarity of Y-EDTMP and Sm-EDTMP, these date should also be relevant to Sm-153-EDTMP.« less