OBJECTIVE. Because CT protocols for staging lung cancer vary and little information exists regarding the diagnostic importance of using IV contrast material. our intent was to evaluate intra- and interobserver agreement in the detection of enlarged mediastinal lymph nodes, comparing IV contrast-enhanced and unenhanced CT. SUBJECTS AND METHODS. Fifty patients with known or suspected bronchogenic carcinoma underwent unenhanced thoracic CT followed by contrast-enhanced CT. Three ob- servers noted enlarged lymph nodes (>10 mm in the short axis) and assigned the enlarged nodes to American Thoracic Society nodal statio)n designations. Enlarged lymph nodes were grouped two ways: by assigning the exact number of enlarged lymph nodes found (zero, o)ne. two, three, four or more), and by assigning whether at least one. or no. enlarged mediastinal lymph nodes were found at a station (“one or none’S). Agreement levels were determined for inter- and intraobserver interpretations using weighted kappa statistics and the McNemar test. RESULTS. The number of enlarged lymph no)des with enhanced CT was II% higher than on unenhanced studies (418 versus 377; p = .044). Numbers of enlarged lymph nodes were different for five stations; however, the numbers were small except for the right upper paratra- cheal station (2R) (contrast-enhanced. 68 enlarged lymph nodes: unenhanced. 44 enlarged lymph nodes; p = .014). With regard to all stations together. intraobserver agreement between contrast-enhanced and unenhanced studies was almost perfect ( range. .85-94). and no dif- ference was found for any observer in the proportion of patients with at least one enlarged lymph node. Interobserver agreement was substantial or almost perfect for the to)tal number of enlarged lymph nodes. For specific statio)ns. the lowest kappa value was .48 at 2R. One ob- server reported more patients with at least one enlarged lymph node with contrast enhance- ment at station 2R (p = .03 1 ). Greater agreement existed between two observers at station 2R with contrast enhancement versus no enhancement ( = .85 versus .48: p = .02). Conclusions matched, and calculations of estimated kappa values gave similar results for determination of the specific number of enlarged lymph nodes at a station and the “one or no)ne’ category. CONCLUSION. We found high agreement for intra- and interobserver interpretations for contrast- enlunced and unenhanced CT, although contrast-enhanced CT revealed more en- larged lymph nodes. especially at station 2R. Received May 27, 1997: accepted after revision October 10, 1997. Presented at the annual meeting of the Radiological Society of North America, Chicago, November-December 1995. E. A. Kazerooni is supported in part by a General Electric Academic Radiology Award, and M. Strawderman is supported by University of Michigan Cancer Center core grant P03-CA46592. 1 Department of Radiology, University of Michigan Hospitals, 1500 E. Medical Center Dr., Taubman Center 2910, Ann Arbor, Ml 48109-0326. Address correspondence to P. N. Cascade. 2Cancer Center, University of Michigan Hospitals, Ann Arbor, Ml 48109. AJR 1998:170:927-931 0361-803X/98/1704-927 ©American Roentgen Ray Society AJR:170, April1998 927 Variability in the Detection of Enlarged Mediastinal Lymph Nodes in Staging Lung Cancer:A Comparison of Contrast-Enhanced and Unenhanced CT Philip N. Cascade1 Barry H. Gross1 Ella A. 1 Leslie E. Quint1 Isaac R. Francis1 Myla Strawderman2 Melvyn Korobkin1 T he CT evaluation of media.stinal lymph nodes is generally accepted as an important element in staging non-small cell lung cancer [ 1 ]. Accurate stag- ing helps to define prognosis and is crucial for selecting the optimum therapeutic approach. Techniques for the CT evaluation of nodal en- largement vary, and the optimum methodology has not been established. Protocols differ with regard to the use of conventional versus helical c-f scanning. slice thickness. hand versus power injection of IV contrast material. or whether contrast material should be used at all 121. Unenhanced scanning has the inherent ad- vantage of avo)iding the risks of contrast mate- rial (induced renal toxicity and hypersensitivity reactions). providing greater patient comfort, and requiring less time and effort to perform. Unenhanced studies also provide savings on costs. including the variable expense of con- trast material and other disposable items such as IV tubing and needles. Several studies have described variability in the detection of enlarged mediastinal lymph nodes. Guyatt et al. 13l. reporting for the Cana- dian Lung Oncology Group. found interob- Downloaded from www.ajronline.org by 52.73.204.196 on 05/16/22 from IP address 52.73.204.196. Copyright ARRS. For personal use only; all rights reserved