Dosimetry for fractionated (131)I-mIBG therapies in patients with primary resistant high-risk neuroblastoma: preliminary results.
This paper describes the development of a protocol for SPECT-based tumor dosimetry for (131)I-mIBG therapy patients with high-risk neuroblastoma. The treatment aims to deliver a whole-body dose of 4 Gy in two fractions. Whole-body retention measurements taken during the first fraction are used to guide the second therapy administration. The tumor dose from 3 patients was assessed by acquiring a minimum of three SPECT scans. Dead-time and triple-energy window scatter corrections were applied. The images were reconstructed using filtered backprojection with a Chang attenuation correction, and a phantom-based calibration factor was used to convert to activity. A monoexponential fit was made to the data, and instantaneous uptake was assumed. Tumor absorbed-dose ratios were used to analyze intrapatient variations, and absolute tumor dosimetry was used to assess interpatient variation. The whole-body dose administered ranged from (3.7 +/- 0.1) Gy to (3.9 +/- 0.3) Gy. This method is more accurate than a weight-based administration method. Despite this, a variation in absorbed tumor dose of 10-103 Gy was observed. All repeat doses were in the same order of magnitude, although 2 patients received a lower tumor dose per MBq from the second therapy owing to a shorter biological half-life. The tumor dosimetry protocol was simple to apply and reproducible, but the errors in image quantitation needed to be evaluated.
Buckley
Susan E
SE
Royal Marsden NHS Foundation Trust, Sutton, Surrey, UK. susan.buckley@icr.ac.uk
Saran
Frank H
FH
Gaze
Mark N
MN
Chittenden
Sarah
S
Partridge
Mike
M
Lancaster
Donna
D
Pearson
Andrew
A
Flux
Glenn D
GD
D019797:3-Iodobenzylguanidine / Q000737:chemistry / Q000627:therapeutic use*; D002675:Child, Preschool; D005260:Female; D006801:Humans; D007457:Iodine Radioisotopes; D008297:Male; D009447:Neuroblastoma / Q000188:drug therapy* / Q000473:pathology / Q000532:radiotherapy*; D011874:Radiometry; D013997:Time Factors
D007457:Iodine Radioisotopes; D019797:3-Iodobenzylguanidine