123I-MIBG Scintigraphy and 18F-FDG PET in Neuroblastoma
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* Nghi Co Nguyen
* Deepika Bhatla
* Medhat M. Osman

**TO THE EDITOR:** We read with great interest a recent article by Sharp et al. (*1*) in which the authors compared the diagnostic utility of 123I-metaiodobenzylguanidine (MIBG) scintigraphy and 18F-FDG PET in neuroblastoma. In this retrospective study, a total of 113 paired 123I-MIBG and 18F-FDG PET scans of 60 patients were compared.

The authors concluded that 18F-FDG PET was superior to 123I-MIBG scanning in detecting stage 1 and 2 neuroblastoma. Only 10 patients, however, had stage 1 or 2 disease, and of these, 5 patients were undergoing imaging for diagnosis and 5 for follow-up, indicating nonuniform patient groups with different clinical questions. Because the methods of statistical analysis were not described in the article, it was difficult to comprehend the results of the confidence intervals. The calculation of confidence intervals usually requires the assumption that the distribution of the sample population is normal; however, given the small sample size of the studied groups with stage 1 and 2, a normal distribution could not be expected. Thus, the conclusion that 18F-FDG PET is superior for depicting stage 1 and 2 neuroblastoma is doubtful. We would appreciate information about the authors' methods of statistical analysis and their comments on the results for stage 1 and 2 neuroblastoma in regard to the statistical power of the tests.

The authors further concluded that 123I-MIBG scanning was superior to 18F-FDG PET in the evaluation of stage 4 neuroblastoma, “especially during initial chemotherapy, primarily because of the better detection of bone or marrow metastases.” In contrast to these findings, Kushner et al. (*2*) reported a study of 51 patients with high-risk neuroblastoma in which 18F-FDG PET was equal or superior to 123I-MIBG scanning for “identifying neuroblastoma in soft tissue and extra-cranial skeletal structures, for revealing small lesions, and for delineating the extent and localizing sites of disease.” Sharp et al. (*1*) mentioned and discussed the findings of Kushner et al. briefly and from another angle; for example, that Kushner et al. “primarily addressed appropriate follow-up for patients with progressive disease after primary tumor resection in the absence of cranial vault lesions.” The authors, however, did not discuss the discrepancy of the results between the 2 studies. We would appreciate a discussion by the authors in this regard.

The authors described 123I-MIBG as being inferior to 18F-FDG PET in stage 1 and 2 neuroblastoma and superior to 18F-FDG PET in stage 4 neuroblastoma, based on the numbers of scans and patients for which either of the 2 modalities detected more lesions. The authors, however, did not discuss whether the better performance of either modality resulted in a change in clinical stage or clinical management. We would appreciate information from the authors on this subject.

## Footnotes

*   COPYRIGHT © 2010 by the Society of Nuclear Medicine, Inc.

## References

1.  1. Sharp SE, Shulkin BL, Gelfand MJ, Salisbury S, Furman WL. 123I-MIBG scintigraphy and 18F-FDG PET in neuroblastoma. J Nucl Med. 2009;50:1237–1243.
    
    [Abstract/FREE Full Text](http://jnm.snmjournals.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6Njoiam51bWVkIjtzOjU6InJlc2lkIjtzOjk6IjUwLzgvMTIzNyI7czo0OiJhdG9tIjtzOjIzOiIvam51bWVkLzUxLzIvMzMwLjIuYXRvbSI7fXM6ODoiZnJhZ21lbnQiO3M6MDoiIjt9) 

2.  2. Kushner BH, Yeung HW, Larson SM, Kramer K, Cheung NK. Extending positron emission tomography scan utility to high-risk neuroblastoma: fluorine-18 fluorodeoxyglucose positron emission tomography as sole imaging modality in follow-up of patients. J Clin Oncol. 2001;19:3397–3405.
    
    [Abstract/FREE Full Text](http://jnm.snmjournals.org/lookup/ijlink/YTozOntzOjQ6InBhdGgiO3M6MTQ6Ii9sb29rdXAvaWpsaW5rIjtzOjU6InF1ZXJ5IjthOjQ6e3M6ODoibGlua1R5cGUiO3M6NDoiQUJTVCI7czoxMToiam91cm5hbENvZGUiO3M6MzoiamNvIjtzOjU6InJlc2lkIjtzOjEwOiIxOS8xNC8zMzk3IjtzOjQ6ImF0b20iO3M6MjM6Ii9qbnVtZWQvNTEvMi8zMzAuMi5hdG9tIjt9czo4OiJmcmFnbWVudCI7czowOiIiO30=)