Dual phase qualitative and quantitative 99mtc-mibi scinfimammography for predicting response to neoadjuvant chemotherapy in breast cancer

To determine the role of dual phase 99mTc-MIBI scintimammography in predicting chemotherapeutic response in breast cancer. Cross-sectional study. Karachi Institute of Radiology and Nuclear Medicine [KIRAN], from September 2004 to March 2005. Female patients with locally advanced breast cancer being planned for the anthracycline-based neoadjuvant chemotherapy were included in this study. All subjects received a 740 MBq bolus intravenous injection of 99mTc-MIBI. Ten minutes and 3 hours post-injection planar images were obtained in prone, lateral and supine positions using double head gamma camera. MIBI washout was scored as follows: > 30% as a positive prognostic test [predicting a poor response to chemotherapy] and < 30% as negative prognostic test [predicting a good response to chemotherapy]. Qualitative analysis of MIBI scans was also performed and categorized as visual wash-out or no visual washout as apparent on the early and delayed images. The criterion for the good and bad response was the reduction of > 50% and < 50% in the tumour burden respectively. Accuracy analysis, Chi-square test and Wilcoxan sign rank test were applied. There were 32 females [mean age: 46.3 years; median age 46 years; age range 33-65 years]. Quantitative dual phase 99mTc-MIBI scintimammography was found to be a good predictor of chemotherapeutic response in breast cancer. These were true positive in 8 patients and true negative in 19 patients with sensitivity [Sens.] 72%, specificity [Spec.] 90%, Positive Predictive Value [PPV] 80%, Negative Predictive Value [NPV] 86.5%, p < 0.03. Receiver Operating Characteristics [ROC] curve analysis demonstrates 30% as a cut-off value for the wash-out in quantitative dual phase MIBI for the prediction of the chemotherapeutic response. In comparison, qualitative scintimammography had Sens. 82%, Spec. 53%, PPV 29%, NPV 93% and p < 0.38. Statistical difference was found between early and delayed uptake ratios in the responders and non-responders. Quantitative dual phase 99mTc-MIBI scintimammography is a simple, reliable, non-invasive and effective tool for predicting the response to neoadjuvant chemotherapy. Furthermore, quantitative assessment is more precise than qualitative [visual wash-out] approach