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Journal of Clinical Oncology, Vol 23, No 12 (April 20), 2005: pp. 2874-2875 © 2005 American Society of Clinical Oncology. DOI: 10.1200/JCO.2005.05.338
Do PET and SNB Reduce the Rate of Elective Neck Dissection? A Hypothesis Still in Need of ValidationDepartment of Therapeutic Radiology, Yale University School of Medicine, New Haven, CT To the Editor: In their recent article, Kovács et al1 report their experience utilizing positron emission tomography (PET), computed tomography (CT), and sentinel node biopsy (SNB) in a prospective cohort of patients with resectable T1-3 squamous cell carcinoma of the oral cavity and oropharynx. This experience represents an important addition to the literature regarding the use of PET in the management of such patients. The authors conclude that a strategy utilizing PET and SNB considerably reduces the number of extensive neck dissections performed when compared with a treatment strategy that relies on only CT. However, the data presented do not necessarily support this conclusion. For the identification of cervical lymph node metastasis, the authors state that CT "had a clear advantage" regarding sensitivity and that PET "had a clear advantage" regarding specificity. However, because these differences were not statistically significant, it is inappropriate to conclude that either PET or CT is better. In addition, administration of high-dose intra-arterial cisplatin after imaging and before SNB or neck dissection could have sterilized microscopic disease and thus artifactually increased the observed false-positive rates for both CT and PET. The authors claim that a strategy using SNB for patients who are cN0 by PET will reduce the number of neck dissections required. They begin with the a priori assumption that an ipsilateral level I-V modified radical neck dissection (MRND) is indicated for all patients with suspected cervical lymph node metastasis. Thus, if PET reveals evidence for cervical metastasis, a modified radical neck dissection is performed. If PET reveals no evidence for cervical metastasis, a modified radical neck dissection is performed only if SNB is positive. The authors state that this strategy markedly reduced the number of neck dissections performed when compared with a CT-based strategy. First, they state in the abstract that 96 of 124 neck sides would have required a neck dissection (either selective or modified radical) on the basis of a CT approach, but only 41 of 124 neck sides actually required dissection with the PET + SNB approach. This statement generates confusion because the CT-based approach assumes that selective neck dissection is performed for all cN0 patients, whereas the PET-based approach assumes that SNB is performed for all cN0 patients. Thus, the authors are comparing two different treatment paradigms, not two different imaging tests. The real comparison should be the difference in neck dissection rates for a PET + SNB approach versus a CT + SNB approach. With the PET-based approach, 41 neck dissections were performed. The number of neck dissections that would have been performed with a CT + SNB approach is theoretically derived from the observed sensitivity and specificity of CT and is approximately 45, but may be as high as 49. Thus, addition of PET spared only four to eight neck sides from dissection. Finally, it should be emphasized that the "unnecessary" neck dissections with the CT + SNB strategy are attributed to an excess in false-positive CT results as compared with PET results. However, all of these excess CT false-positive cases were evaluated with only SNB, a technique that may underestimate the true likelihood of cervical metastasis when compared with the gold standard of level I-V neck dissection.2 Thus, the reported CT false-positive rate may be artifactually elevated. If the false-positive rate of CT is truly lower than reported in this study, then the number of "unnecessary" neck dissections would decrease, further narrowing the difference between CT- and PET-based approaches. In summary, this article supports the hypothesis that excellent outcomes can be achieved using SNB to evaluate the clinically negative neck. However, there appears to be no clinically or statistically significant difference between PET and CT when integrated with SNB in the staging of patients with head and neck cancer. Authors' Disclosures of Potential Conflicts of Interest The authors indicated no potential conflicts of interest. Acknowledgment The authors whish to acknowledge Dr Gabriel N. Hortobagyi for reviewing this letter. REFERENCES
1. Kovács AF, Dobert N, Gaa J, et al: Positron emission tomography in combination with sentinel node biopsy reduces the rate of elective neck dissections in the treatment of oral and oropharyngeal cancer. J Clin Oncol 22:3973-3980, 2004 2. Ross GL, Shoaib T, Soutar DS, et al: The First International Conference on Sentinel Node Biopsy in Mucosal Head and Neck Cancer and adoption of a multicenter trial protocol. Ann Surg Oncol 9:406-410, 2002[CrossRef][Medline]
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Copyright © 2005 by the American Society of Clinical Oncology, Online ISSN: 1527-7755. Print ISSN: 0732-183X
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