Undeserved bad press for bone scans: reply

Abstract

Undeserved bad press for bone scans: reply Dear SirWe 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 information is provided by the m I B G 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 collapses in the light of our original sentence: "123I-mIBG is able to detect early tumoural deposits in the bone marrow before osseous invasion occurs as shown on 99mTc-MDP bone scans." Our conclusion is based on the following results as reported in our article: a) Thirty-eight mIBG scans showed no visualization 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 m I B G 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 cannotalthough techniques can always be improved -agree with his judgement that the bone scans are of "poor quality". As we mentioned in the article, this study was a retrospective one. Subsequent to personal communication with Dr. I. Roca from Spain at the '92 EANM congress in Lisbon, we have made it departmental practice 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 comment about " Fig. 2", claiming that the knees are not normal. Considering the great range of 99mTc-MDP uptake in the skeleton, we must be very cautious in interpreting the scans and indeed focussing attention too exclusively 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][3][4].As we noted in our paper [2], the conclusion that m I B G scan is superior to 99mTc-MDP bone scan in detecting small foci of bone metastases and/or bone marrow involvement is not confined to our group but rather is shared by other groups [5][6][7][8][9]. It is true that 10% of neuroblastomas fail to accumulate m I B G [9] while MDP bone scan clearly demonstrates the inv...