Evaluation of semi-quantitative scoring system for metaiodobenzylguanidine (mIBG) scans in patients with relapsed neuroblastoma.
BACKGROUND
The purpose of this study was to determine the accuracy of two semi-quantitative scoring systems to assess response to (131)I-metaiodobenzylguanidine (mIBG) therapy in recurrent neuroblastoma.


METHODS
Diagnostic mIBG scan pairs (n = 57) were collected for patients who underwent (131)I-mIBG therapy for relapsed neuroblastoma. Two scoring systems were designated: Method 1, which divided the body into nine segments to view osteomedullary lesions with an additional tenth segment to assess soft tissue involvement; and Method 2, which divided the body into seven segments without a corresponding compartment for soft tissue involvement. Four nuclear medicine physicians independently assigned extension and intensity scores utilizing both methods, and separately recorded their impression of whether the post-therapy scan had improved, not changed, or worsened. Inter- and intra-observer concordance and correlation with overall response and progression-free survival (PFS) were performed.


RESULTS
Method 1 produced the highest inter-observer concordance and was used to calculate the relative extension scores (post-therapy score divided by pre-therapy score), which correlated significantly with overall response. Patients who achieved complete response (CR) or partial response (PR) (n = 21) had lower relative extension scores, compared to those without response (P < 0.001). The readers' overall impression associated highly (P < 0.001) with the relative extension scores though results were less quantitative. Concordance was higher if initial scores were >5. Relative extension score did not predict PFS.


CONCLUSIONS
Semi-quantitative scoring of mIBG scans provides a more reliable method of assessing response in patients with relapsed neuroblastoma than qualitative impression. The reproducibility and high inter-observer concordance makes mIBG score an important component of overall response criteria in patients with recurrent neuroblastoma.
Messina
Julia A
JA
Department of Pediatrics, University of California, San Francisco, California 94143, USA.
Cheng
Su-Chun
SC
Franc
Benjamin L
BL
Charron
Martin
M
Shulkin
Barry
B
To
Bao
B
Maris
John M
JM
Yanik
Gregory
G
Hawkins
Randall A
RA
Matthay
Katherine K
KK
D019797:3-Iodobenzylguanidine; D000293:Adolescent; D000328:Adult; D002648:Child; D002675:Child, Preschool; D018572:Disease-Free Survival; D005260:Female; D006801:Humans; D007223:Infant; D007231:Infant, Newborn; D008297:Male; D009364:Neoplasm Recurrence, Local; D009447:Neuroblastoma / Q000000981:diagnostic imaging* / Q000401:mortality; D015588:Observer Variation; D011877:Radionuclide Imaging; D019275:Radiopharmaceuticals; D015203:Reproducibility of Results
D019275:Radiopharmaceuticals; D019797:3-Iodobenzylguanidine