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Journal of Clinical Oncology, Vol 25, No 36 (December 20), 2007: pp. 5838-5839 © 2007 American Society of Clinical Oncology. DOI: 10.1200/JCO.2007.14.4469
In Reply:Department of Radiology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
Department of Nuclear Medicine, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium
Department of Urology, Cliniques Universitaires Saint-Luc, Université Catholique de Louvain, Brussels, Belgium We appreciate the interest of Dr Venkitaraman and colleagues in our recent article.1 We wish to address their comments. Dr Venkitaraman and colleagues seem to be intrigued by the superior results of magnetic resonance imaging (MRI) over bone scan (BS) to detect bone metastases in patients with prostate cancer (PCa) at high risk for metastases, and question our categorization of results. As detailed in the article, we used the same clear classification system of the results into three well-defined categories (positive, negative, or equivocal), and the same statistical approach (consisting of categorizing the equivocal readings as suggestive for malignancy in patients with no metastasis and categorizing the equivocal readings as benign in patients with metastasis) for all imaging tests (BS, targeted radiographs [TXR], and MRI of the bone marrow). We do agree that the term "equivocal" covers a wide range of results that could have been termed "possible," "suspicious," "likely," "highly suspicious," "almost certain," and so on. The generic term does not matter: this category encompasses all situations in which imaging findings could not be categorized confidently as positive or negative, regardless of the level of incertitude. This classical approach was used for all imaging techniques. There is no bias there. We do agree that the example illustrated in the Figure 1 of our article is highly suggestive of skeletal metastasis on the basis of the results of the BS/TXR work-up. However, we do not state that "further confirmation with other imaging including MRI" is required, although it would be requested in clinical routine whenever a consolidate answer is required. We do demonstrate that a one-step noninvasive examination, MRI, results in immediate certitude with regard to the metastatic status of this patient.
We cannot agree with Dr Venkitaraman and colleagues when they invoke conventional wisdom or suggestions to make sometimes life-threatening or invalidating therapeutic decisions. Conventional wisdom may be acceptable in clinical practice to assess a fracture risk—it becomes questionable when it comes to definitive decisions in oncology. In 1958, Galbraith coined this term "conventional wisdom" to define "the ideas which are esteemed at any time for their acceptability," and pointed out that there may be important differences between what is acceptable (the territory of the conventional wisdom) and what is true. Conventional wisdom is often seen as an obstacle to introducing new theories—a cause of inertia.2 Our study demonstrated that a fair proportion of our patient staging using the current BS/TXR work-up was not true according to the gold standard. Is this acceptable? Let us take examples from our series. The example of a middle-aged man just being diagnosed with localized high risk PCa (Gleason score 8), with a normal abdominal computed tomography and normal BS. Based on conventional wisdom and current work-up, he would undergo a radical prostatectomy, although metastatic status is evident at MRI (Fig 1). In more advanced disease and clinical trials aimed at validating bone-specific agents, we maintain that it is not acceptable to rely on most likely positive end points and on a conventional wisdom–based appreciation. Dr Venkitaraman and colleagues emphasize that if a BS uptake is not explained by a benign lesion on radiographs, it is most likely to represent a malignant process. Another conventional wisdom points toward the opposite direction, suggesting that solitary rib lesions in cancer patients detected at BS with normal radiographs are most likely associated with a benign etiology.3 There seem to be variations in the conventional wisdom. We confirm that "none of the patients without metastasis on MRI of the axial skeleton had metastasis elsewhere." As stated in the article, isolated abnormal uptake outside the axial skeleton on BS was only observed in four patients, due to Paget disease in one case, and to rib fractures in three cases, as confirmed by TXR and follow-up. We also confirm that MRI had no false-negative result in terms of patient staging, given that each patient with peripheral metastases also had metastases within the spine and/or pelvis at MRI. The inclusion criteria of the study (high-risk PCa) were clearly defined and addressed by two patient populations reflecting daily therapeutic decisions in oncology: at diagnosis or later when they faced an increasing PSA. Whether BS may present more weaknesses in one of theses situations does not influence the study of available imaging tests in both situations. Evaluation of the benefit of obtaining true staging in each of these situations was beyond the purpose of our study. Finally, we do not state that MRI could replace BS as the initial and sole imaging modality for staging all PCa patients. We do demonstrate that MRI surpasses the current imaging strategy used for staging for bone metastases in a clearly defined patient population at high risk for bone metastases. Knowing whether staging for bone metastases is necessary in each newly diagnosed PCa, and whether BS may stay useful in this setting, was behind the scope of our work. There is place for large multicentric studies in well-defined groups of patients to assess and confirm the clinical efficacy of MRI as the initial tool for staging for bone metastases in PCa. AUTHORS' DISCLOSURES OF POTENTIAL CONFLICTS OF INTEREST The author(s) indicated no potential conflicts of interest.
ACKNOWLEDGMENTS Supported by an educational grant from the nonprofit organization Fondation Saint-Luc (F.E.L. and B.T.). REFERENCES
1. Lecouvet FE, Geukens D, Stainier A, et al: Magnetic resonance imaging of the axial skeleton for detecting bone metastases in patients with high-risk prostate cancer: Diagnostic and cost-effectiveness and comparison with current detection strategies. J Clin Oncol 25:3281-3287, 2007 2. Galbraith JK: The concept of the conventional wisdom, in The Affluent Society. London, United Kingdom, Hamish Hamilton, 1958, pp 6-17 3. Tumeh SS, Beadle G, Kaplan WD: Clinical significance of solitary rib lesions in patients with extraskeletal malignancy. J Nucl Med 26:1140-1143, 1985
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Copyright © 2007 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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) are identified on the magnetic resonance imaging studies as areas of low signal intensity on T1-weighted images of the (C) spine and (D) pelvis. Metastatic status was confirmed at follow-up.
