European Journal of

Nuclear Medicine Letter to the editor

Undeserved bad press for bone scans: reply

Dear Sir

We are really astonished by the style of Dr. Gordon's letter [1], which exposes us to what we consider to be unjustifiable criticism. Our paper [2] was not intended to - nor does it - place bone scans in an unfavourable light; it simply concludes that in certain situations more infor- mation is provided by the mIBG scan.

1. In Dr. Gordon's letter the meaning of the sentence 'q23I-MIBG is able to detect early tumoral diposits [sic] ... before 99mTc-MDP bone scans" is distorted by the omission signalled by dots. His argument simply collap- ses in the light of our original sentence: "123I-mIBG is able to detect early tumoural deposits in the bone mar- row before osseous invasion occurs as shown on 99mTc- MDP bone scans." Our conclusion is based on the fol- lowing results as reported in our article: a) Thirty-eight mIBG scans showed no visualiza- tion of the skeleton: the matching 99mTc-MDP bone scans were also normal. b) Seven cases with diffuse m I B G uptake in the skeleton appeared as normal on the 99mTc-MDP scans. c) Of 27 cases showing focally increased mIBG uptake in the skeleton with or without diffuse uptake, only 18 demonstrated a hot spot on the bone scintigram.

It is evident that these results allow us to draw the above-mentioned conclusion. With the best will in the world it cannot be concluded that MDP is better or even as good as mIBG in this respect.

2. While we thank Dr. Gordon for pointing out that the fibula is indistinguishable from the tibia, we cannot - although techniques can always be improved - agree with his judgement that the bone scans are of "poor qua- lity". As we mentioned in the article, this study was a retrospective one. Subsequent to personal communica- tion with Dr. I. Roca from Spain at the '92 EANM congress in Lisbon, we have made it departmental prac- tice to take images of the knees at internal rotation in order to distinguish the fibula from the tibia.

3. Again, we cannot agree with Dr. Gordon's com- ment about "Fig. 2", claiming that the knees are not normal. Considering the great range of 99mTc-MDP up- take in the skeleton, we must be very cautious in inter- preting the scans and indeed focussing attention too ex- clusively on the presence of metastasis may sometimes be misleading and may induce over-diagnosis.

We leave it up to readers to judge whether or not, in the examples shown by us, it will ever be possible for

Dr. Gordon's high-quality 99mTc-MDP images to achieve more than a suspicion of metastasis in the delineated sites of uptake. This ~ts because of the non-specificity of 99mTc-MDP while 123I-mIBG shows highly specific bony uptake without any false-positive results [2-4].

As we noted in our paper [2], the conclusion that mIBG scan is superior to 99mTc-MDP bone scan in de- tecting small foci of bone metastases and/or bone mar- row involvement is not confined to our group but rather is shared by other groups [5-9]. It is true that 10% of neuroblastomas fail to accumulate mIBG [9] while MDP bone scan clearly demonstrates the involved bony sites and this may cause an underestimation of tumour dissemination [4, 6, 10]. This situation does not change the facts. Two different techniques each can be very va- luable in themselves; in any given situation, one will be better than the other, while their combined use may come closest to the ideal. What we have written in our paper does nothing other than to clearly suggest the combined use of 99mTc-MDP scan and 123I mIBG scan as complementary methods.

4. We entirely agree that the excellent publication, Atlas of Bone Scintigraphy in the Developing Paediatric Skeleton, which was prepared by distinguished authors, including Dr. Gordon, will certainly help us in obtaining better images and in interpretation. In any case, such an excellent work does not require any advertisement.

In conclusion we still believe that the tone of Dr. Gordon's letter is unworthy and his criticism in the last analysis is not well grounded. "Amicus Plato, sed magis arnica veritas."

On behalf of the authors [2],

Kaan Osmanagaoglu Department of Radiotherapy and Nuclear Medicine University Hospital De Pintelaan 185 B-9000 Ghent, Belgium

References

1. Gordon I. Undeserved bad press for bone scans. Eur J Nucl Med 1994; 21: 466.

2. Osmanagaoglu K. Lippens M, Benoit Y, Obrie E, Schelstraete K, Simons M. A comparison of iodine-123-mIBG scintigra- phy and single bone marrow aspiration biopsy in the diagnosis and follow-up of 26 children with neuroblastoma. Eur J Nucl Med 1993; 20:1153-1160.

3. Lumbroso JD, Guermazi F, Hartmann O, Coomaert S, Rabari- son Y, Lecl~re JG, Counaet D, Bayle C, Cailland JM, Lemerle J, Parmentier C. Meta-iodobenzylguanidine (mIBG) scan in

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neuroblastoma: sensitivity and specificity. A review of 115 scans. Prog Clin Biol Res 1988; 271: 689.

4. Shulkin BL, Shapiro B, Hutckinson RJ, Sisson JC, Mallette S, Mudgett EE. Comparison of bone and 131 I-mIBG scanning for the detection of skeletal and extraskeletal neuroblastoma. EurJNuclMed 1991; 18: 553.

5. Jacobs A, Delree M, Desprechins B, Otten J, Ferster A, Jonckheer MH, Mertens J, Ham HR, Piepsz A. Consolidating the role of I-mIBG scintigraphy in childhood neuroblastoma: five years of clinical experience. Pediatr Radiol 1990; 20: 157.

6. Bouvier JF, Philip T, Chauvot P, Brunat Mentigny M, Du- crettet F, Ma'iassi N, Lahn~che BE. Pitfalls and solutions in

neuroblastoma diagnosis using radioiodine mIBG: our expe- rience about 50 cases. Prog CIin BiolRes 1988; 271: 707.

7. Shulkin BL, Shen SW, Sisson JC, Shapiro B. Iodine-131 mIBG scintigraphy of the extremities in metastatic pheochro- macytoma and neuroblastoma. J Nucl Med 1987; 28:315.

8. Hibi S, Todo S, Imashuku S, Miyazaki T. 131 I-Metaiodo- benzylguanidine scintigraphy in patients with neuroblastoma. Pediatr RadioI 1987; 17: 308. Shulkin B, Shapiro B. Editorial. JNucl Med 1993; 34: 865. Gordon I, Peters AM, Gutman A, Morony S, Dicks-Mireaux C, Pritchard J. Skeletal assessment in neuroblastoma - the pit- falls of iodine-123-mIBG scans. J Nucl Med 1990; 31: 129.

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European Journal of Nuclear Medicine Vol. 21, No. 10, October 1994