Early Detection of Cancer: Evaluation of MR Imaging Grading Systems in Patients with Suspected Nasopharyngeal Carcinoma
Ann D. King, John K. S. Woo, Qi Yong H. Ai, Frankie Mo, Tiffany Y. So, W.K. Lam, Irene O L Tse, Alexander C. Vlantis, Natalie Yip, Edwin P. Hui, Brigette Ma, Rossa W. K. Chiu, A.T.C. Chan, Yuk Ming Dennis Lo, K.C. Allen Chan
Abstract
<h3>BACKGROUND AND PURPOSE:</h3> We evaluated modifications to our contrast-enhanced MR imaging grading system for symptomatic patients with suspected nasopharyngeal carcinoma, aimed at improving discrimination of early-stage cancer and benign hyperplasia. We evaluated a second non-contrast-enhanced MR imaging grading system for asymptomatic patients from nasopharyngeal carcinoma plasma screening programs. <h3>MATERIALS AND METHODS:</h3> Dedicated nasopharyngeal MR imaging before (plain scan system) and after intravenous contrast administration (current and modified systems) was reviewed in patients from a nasopharyngeal carcinoma–endemic region, comprising 383 patients with suspected disease without nasopharyngeal carcinoma and 383 patients with nasopharyngeal carcinoma. The modified and plain scan systems refined primary tumor criteria, added a nodal assessment, and expanded the system from 4 to 5 grades. The overall combined sensitivity and specificity of the 3 systems were compared using the extended McNemar test (a χ<sup>2</sup> value <math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" id="i1" overflow="scroll"><mrow><msubsup><mi>χ</mi><mrow><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow><mn>2</mn></msubsup></mrow></math>> 5.99 indicates significance). <h3>RESULTS:</h3> The current, modified, and plain scan MR imaging systems yielded sensitivities of 99.74%, 97.91%, and 97.65%, respectively, and specificities of 63.45%, 89.56% and 86.42%, respectively. The modified system yielded significantly better performance than the current (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" id="i2" overflow="scroll"><mrow><msubsup><mi>χ</mi><mrow><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow><mn>2</mn></msubsup></mrow></math> = 122) and plain scan (<math xmlns="http://www.w3.org/1998/Math/MathML" display="inline" id="i3" overflow="scroll"><mrow><msubsup><mi>χ</mi><mrow><mrow><mo>(</mo><mn>2</mn><mo>)</mo></mrow></mrow><mn>2</mn></msubsup></mrow></math> = 6.1) systems. The percentages of patients with nasopharyngeal carcinoma in grades 1–2, grade 3, and grades 4–5 for the modified and plain scan MR imaging systems were 0.42% and 0.44%; 6.31% and 6.96%; and 90.36% and 87.79%, respectively. No additional cancers were detected after contrast administration in cases of a plain scan graded 1–2. <h3>CONCLUSIONS:</h3> We propose a modified MR imaging grading system that improves diagnostic performance for nasopharyngeal carcinoma detection. Contrast was not valuable for low MR imaging grades, and the plain scan shows potential for use in screening programs.