Departments of Nuclear Medicine, Medical School and Hospital, Johann Wolfgang Goethe-University of Frankfurt and RheinischeFriedrich Wilhelms, University of Bonn, Bonn 53127, Germany
Address correspondence to: Christian Menzel, M.D., Klinikum der Johann Wolfgang Goethe-Universitat, Frankfurt am Main, Klinik fur Nuklearmedizin Universitatsklinikum, Theodor-Stern-Kai 7, Frankfurt 60590, Germany. E-mail: christian.menzel{at}em.uni-frankfurt.de.
To the editor:
We have read with great interest the article by Mazzaferri et al. that appeared in a recent issue of JCEM (1). The issue of serum thyroglobulin (TG) after stimulation with recombinant human TSH (rhTSH) (Thyrogen, Genzyme Corporation, Cambridge, MA) as the sole parameter for a follow-up of thyroid carcinoma has been addressed in a number of studies recently. This article mainly summarizes the results of studies previously published by the writers.
Based on their review of various publications, Mazzaferri and co-workers consider stimulated, namely rhTSH-stimulated, human TG (hTG) tests sufficient for a follow-up of low-risk papillary thyroid cancer. By contrast, in their opinion the use of whole body scintigraphy after diagnostic I-131 (dWBS) activities should be discouraged.
Although in general we may agree on the principal theory that dWBS possibly is of questionable value in a certain number of low-risk patients with papillary thyroid carcinoma, in regard to the current paper we first of all would not accept a title stating that its content was a consensus report. In fact, this consensus was achieved by a very selective choice of authors and largely on the basis of papers that these authors had previously published. From our point of view, this should be stated more clearly to avoid any misunderstandings.
Secondly, this consensus not to make use of dWBS in the future was achieved without sufficiently considering the professional opinion of nuclear medicine specialists, which could have helped in different ways.
As we have pointed out already, there may be an agreement concerning low-risk patients who may not benefit from an additional dWBS, thus allowing these costs to be saved, but we would oppose the definition of low-risk patients as given in the paper. Although we continue to learn more about the use of rhTSH and for example the different effectiveness of I-131 after its use compared with thyroid hormone withdrawal, we should keep this group limited to papillary carcinomas of patients younger than 45 yr and to a primary tumor size pT1 without metastases (also we would suggest using the new UICC classification, because alternatives are confusing). We recommend this due to our experience that stimulated hTG, also after endogenous or rhTSH stimulation, may remain below 2 ng/ml, whereas there is still evidence of differentiated thyroid cancer in the scintigraphy and especially after positron emission tomography (PET) imaging with F18-deoxyglucose, although our patients were not selected for a low-risk profile. As we keep on learning about the use of rhTSH, the stereotype measurement of hTG 72 h after its application may not even represent the true peak level of hTG in all patients, at least according to our own data. Thus, any threshold must be considered critically.
We would also take issue with the follow-up algorithm noted in the paper and shown in Fig. 1. This group of low-risk patients (still to be defined) who display increased stimulated hTG should immediately receive a check for urinary iodine excretion to rule out iodine contamination being followed by a diagnostic or therapeutic amount of I-131. After all, I-131 remains the only systemic therapy available for these patients, and, regardless of any discussion whether or not uptake may or may not be present, it remains a prerogative for the therapy planning just to know this in the individual patient. This concept may be complemented by PET and/or computed tomography/magnetic resonance imaging at an earlier point in the algorithm. Neck ultrasound is a routine investigation and, thus, is always applied. If positive, other tumor sites are not ruled out. If negative, a correlate for an elevated hTG is missing. Chest x-ray from our point of view is cheap but out of date in the presence of the high-resolution multislice computed tomography and PET.
We would finally oppose any suggestion that it is cost effective simply to exchange dWBS for rhTSH. Although the information obtained by dWBS may not be needed in all cases, its diagnostic and therapeutic value in questionable cases is unsurpassed. rhTSH in contrast is a tool to avoid the discomfort of thyroid hormone withdrawal and, in doing so, represents important progress. However, in a diagnostic setting this has no additional positive impact at all compared with the much cheaper option of thyroid hormone withdrawal. Although we may therefore consider the possibility of doing without dWBS in certain patients in the future, we do not consider that this option should be connected closely to the use of rhTSH, which itself is still associated with a number of unsolved problems.
Received June 3, 2003.
References
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