Iodine-131-metaiodobenzylguanidine dosimetry in cancer therapy: risk versus benefit.
In the treatment of neural crest tumors, such as pheochromocytoma, with[131I]MIBG, bone marrow toxicity limits the amount of administered activity and, thus, a therapeutically useful tumor dose.


METHODS
We calculated tumor doses in a series of diagnostic studies with [123I]MIBG using accurate quantification of SPECT and planar scintigraphy. By extrapolating diagnostic results to therapeutic activities of [131I]MIBG, we could compare the results with whole-body doses from a series of therapies.


RESULTS
The tumor dose was DT = 2.2 mGy MBq(-1) (median value of 27 measurements, range 0.04 < or = DT < or = 20 mGy MBq(-1) and the whole-body dose in a series of 16 patients undergoing 50 therapies was DWB = 0.12 +/- 0.04 mGy MBq(-1) (mean +/- s.d.). The therapeutic ratio varied between 130 to below 10 in some patients.


CONCLUSIONS
The results were compared with published data. We found clearly skewed distribution of tumor doses, with a majority of tumors receiving only a few mGy per MBq administered activity. In some patients, however, doses did reach 20 mGy MBq(-1).
Tristam
M
M
Department of Nuclear Medicine, Southampton General Hospital, United Kingdom.
Alaamer
A S
AS
Fleming
J S
JS
Lewington
V J
VJ
Zivanovic
M A
MA
D019797:3-Iodobenzylguanidine; D000293:Adolescent; D000328:Adult; D000970:Antineoplastic Agents / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D002648:Child; D006801:Humans; D007457:Iodine Radioisotopes / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D007462:Iodobenzenes / Q000008:administration & dosage* / Q000009:adverse effects / Q000627:therapeutic use; D009447:Neuroblastoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D010673:Pheochromocytoma / Q000000981:diagnostic imaging / Q000532:radiotherapy*; D011879:Radiotherapy Dosage; D012306:Risk; D015899:Tomography, Emission-Computed, Single-Photon
D000970:Antineoplastic Agents; D007457:Iodine Radioisotopes; D007462:Iodobenzenes; D019797:3-Iodobenzylguanidine