One single-time-point kidney uptake from OctreoScan correlates with number of desintegrations measured over 72 hours and calculated for the 6.7 hours half-life nuclide (177)Lu.
OBJECTIVE
In somatostatin receptor-targeted therapy, renal toxicity is an expected side effect, and therefore pretherapeutic dosimetry based on a measured kinetics is preferable. In contrast, a convenient one single-time-point scan might also reveal relevant information on expected dose to organs. However, very early time points might not reflect the true retention by the renal cortex and therefore be of limited value to predict dose for the long-lived 177Lu.


METHODS
Dosimetry with 111In-octreotide was performed in 24 patients, and the number of disintegrations (ND) were calculated for 177Lu. Uptake values for each time point were correlated with ND.


RESULTS
The fitting algorithm was best with biexponential equations in 18 patients. Mean biologic half-life of the alpha component was 6 hours (+/-12 hours) and for the beta component 82 hours (+/-38 hours). For the early time points, correlation with ND was generally poor. For later time points, correlation increased markedly after 4 hours (4 hours: r = 0.83, 72 hours: r = 0.93) and were also capable of predicting dosimetry to some extent.


CONCLUSIONS
In conclusion, thorough quantification of the 4 hours single-time-point scans seems to be enough to predict the expected renal dose for radionuclide therapies to some degree.
Klinik und Poliklinik für Nuklearmedizin, Universitätsmedizin Mainz, Mainz, Germany. matthias.miederer@unimedizin-mainz.de
Matthias
M
Miederer
Helmut
H
Reber
Andreas
A
Helisch
Christian
C
Fottner
Matthias
M
Weber
Mathias
M
Schreckenberger
D001692:Biological Transport; D005260:Female; D006207:Half-Life; D006801:Humans; D007668:Kidney / Q000000981:diagnostic imaging* / Q000378:metabolism* / Q000473:pathology / Q000528:radiation effects; D007700:Kinetics; D008187:Lutetium / Q000009:adverse effects* / Q000378:metabolism* / Q000627:therapeutic use; D008297:Male; D018358:Neuroendocrine Tumors / Q000000981:diagnostic imaging / Q000378:metabolism / Q000473:pathology / Q000532:radiotherapy; D015282:Octreotide / Q000031:analogs & derivatives; D009929:Organ Size / Q000528:radiation effects; D011868:Radioisotopes / Q000009:adverse effects* / Q000378:metabolism* / Q000627:therapeutic use; D011874:Radiometry; D011877:Radionuclide Imaging
D011868:Radioisotopes; C094279:indium-111-octreotide; D008187:Lutetium; D015282:Octreotide