Dual phase qualitative and quantitative 99mTc-MIBI scintimammography for predicting response to neoadjuvant chemotherapy in breast cancer.

OBJECTIVE To determine the role of dual phase 99mTc-MIBI scintimammography in predicting chemotherapeutic response in breast cancer. STUDY DESIGN Cross-sectional study. PLACE AND DURATION OF STUDY Karachi Institute of Radiology and Nuclear Medicine (KIRAN), from September 2004 to March 2005. METHODOLOGY 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. RESULTS 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. CONCLUSION 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.