Evaluation of scintimammography as an additional test to conventional mammography in detection of breast cancer

OBJECTIVES AND DESIGN: Scintimammography using Tc-99m MIBI is becoming established as a second line diagnostic test for the detection of breast cancer in patients with suspected primary disease. Though most published clinical studies compare scintimammography (SMM) with mammography (XMM), in clinical practice they are likely to be used sequentially with the scintimammography following the mammography. MATERIALS AND METHODS: To determine the possible accuracy of such an approach, receiver operator characteristic (ROC) curves were produced for SMM, XMM and a combination of both studies performed over 2 years period on 162 suspicious lesions in 154 patients with no previous history of breast cancer. Each scan was reported in 5 grades: 1-normal or definitely benign; 2-possibly normal or possibly benign; 3-equivoval; 4-probably cancer; 5-definitely cancer. The results have been verified by pathological examination of biopsy material obtained from each suspicious mass. RESULTS: There were 102 malignant breast tumours and 60 non-malignant breast lesions. SMM correctly diagnosed 89 breast cancers, and was false negative in 13 cases. It was true negative in 36 benign breast lesions. The sensitivity of SMM was 87%, specificity 65%, PPV 81% and NPV 75%. XMM diagnosed correctly 70 malignant tumours. The sensitivity, specificity, PPV and NPV for XMM were respectively: 69%, 72%, PPV 81% and NPV 57%. However, if a combination of the two methods is used the overall diagnostic accuracy was as follows: 92%, 80%, 89% and 86%. Evaluation of index area under ROC curve allows in both diagnostic methods XMM and SMM results as follows: 0.79 and 0.83. Additional sequence imaging allows 0.94. Combined XMM and SMM in suspected primary breast cancer patients has higher diagnostic accuracy than each method separately (p < 0.05). CONCLUSION: This study shows that the combination of mammography and scintimammography produces more accurate results than either modality alone this is how these test should be performed in clinical practice.