Purpose: To compare the diagnostic accuracy and incremental diagnostic role of quantitative indices of early and delayed lesion to non‐lesion ratios (L/Ns) in the detection of primary breast cancer.
Material and Methods: Double‐phase 99mTc MIBI scintimammography (SMM) (early 10 min, delayed 3 h) was performed after injection of 750 MBq of 99mTc MIBI in 446 highly suspected breast cancer patients (malignant: 311, benign: 135). For visual analysis, five scoring methods were used, and, for quantitative analysis, early and delayed L/Ns were calculated. Receiver operating characteristic curve (ROC) analyses were performed to determine the optimal visual grade, and to calculate cut‐off values of quantitative indices for differentiation of malignant and benign diseases and to investigate whether the quantitative indices could provide incremental diagnostic values in addition to visual analysis.
Results: Optimal visual grades were above 4 and 5 in the detection of breast cancer. Sensitivity was 84.2% and specificity 79.3%; the area under the curve (AUC) was 0.832 (95% CI, 0.794–0.866) and standard error was 0.019. Early and delayed L/Ns of malignant breast disease were significantly higher than those of benign disease (early: 2.01±0.99 versus 1.13±0.26 (P<0.001); delayed: 1.68±0.69 versus 1.11±0.23 (P<0.001)). The optimal L/Ns for the detection of primary breast cancer were 1.27 for early and 1.12 for delayed imaging. When early L/N 1.27 was used as cut‐off value for the detection of primary breast cancer, the sensitivity of SMM was 77.8% and specificity 85.2%. The AUC was 0.856 (95% CI, 0.820–0.888). When delayed L/N 1.12 was used, sensitivity and specificity were 81.4% and 78.5%, respectively. The AUC was 0.834 (95% CI, 0.796–0.867). The ROC comparison of early and delayed L/N showed no statistical difference in the detection of malignant breast disease (P = 0.403). When the delayed L/N was added to the early one, early plus delayed quantitative analysis (E+D) showed 86.5% sensitivity and 74.8% specificity. However, the AUCs of E+D (0.854, 95% CI, 0.767–0.842) and early L/N (E) (0.856) showed no statistical difference (P = 0.614). When grades 4 and 5 were used as cut‐off visual grade, sensitivity and specificity were 84.2% and 79.3%, respectively. When the E was added to visual grade, visual plus early L/N (V+E) showed 89.4% sensitivity and 77% specificity. The AUC of V+E (0.867, 95% CI, 0.832–0.897) was significantly higher than that of visual analysis (V) (0.832, 95% CI, 0.794–0.866, P<0.001). When the delayed L/N (D) was added to visual grade, visual plus delayed L/N (V+D) showed 89.4% sensitivity and 74.1% specificity. The AUCs of V+D (0.852, 95% CI, 0.816–0.884) and V revealed no statistical differences (P = 0.052).
Conclusion: From this study, the optimal visual grades for diagnosis of breast cancer were grades 4 and 5; the cut‐off values of L/Ns were 1.27 for early and 1.12 for delayed imaging. It was also found that early L/Ns provide incremental value in addition to visual analysis. However, delayed L/N revealed no incremental value. Therefore, the delayed image should not be routinely performed for purposes of primary breast cancer detection
