Prediction of the usefulness of combined mammography and scintimammographyin suspected primary breast cancer using ROC curves

The aim of this study was to compare the accuracy of Tc-99m-methoxyisobutyl isonitrile scintimammography (SMM) and conventional mammography in patients presenting with suspected primary breast cancer. Receiver-operating-charac teristic (ROC) curve analysis was applied to determine if a combination of x-ray mammography (XMM) and SMM was more accurate than a single test alone. Methods: The results of SMM, XMM, and a combination of both studies perfor med over a 3-y period on 374 suspicious lesions in 353 patients with no pre vious history of breast cancer were reviewed. Each scan report was reviewed and graded as follows: grade 1, definitely normal or benign; grade 2, prob ably normal or benign; grade 3, equivocal; grade 4, probably cancer; and gr ade 5, definitely cancer, The results were verified by pathologic examinati on of biopsy material obtained from each suspicious mass. ROC curves were g enerated from these results. Results: There were 204 malignant breast tumor s and 170 nonmalignant breast lesions. SMM diagnosed correctly 181 breast c ancers and was true-negative in 122 benign breast lesions: sensitivity, 89% ; specificity, 71%; positive predictive Value (PPV), 79%; and negative pred ictive Value (NPV), 84%. XMM diagnosed correctly 143 malignant tumors and w as true-negative in 117 nonmalignant lesions. The sensitivity, specificity, PPV, and NPV for XMM were 70%, 69%, 73%, and 66%, respectively Using a com bination of the two tests, the combined sensitivity was 93%, specificity wa s 72%, PPV was 80%, and NPV was 90%. Using the index of the area under the ROC curve obtained by the rating method showed that the combination of XMM and SMM was significantly more accurate than either of the individual tests if performed alone (P < 0.05). Conclusion: This study shows that the combi nation of XMM and SMM produces more accurate results than either modality a lone, Therefore, if there is doubt about the accuracy of XMM, SMM should be used as the second-line test in breast imaging.