Comparison of Tc-99m maraciclatide and Tc-99m sestamibi molecular breast imaging in patients with suspected breast cancer

BACKGROUND Molecular breast imaging (MBI) performed with 99mTc sestamibi has been shown to be a valuable technique for the detection of breast cancer. Alternative radiotracers such as 99mTc maraciclatide may offer improved uptake in breast lesions. The purpose of this study was to compare relative performance of 99mTc sestamibi and 99mTc maraciclatide in patients with suspected breast cancer, using a high-resolution dedicated gamma camera for MBI. Women with breast lesions suspicious for malignancy were recruited to undergo two MBI examinations-one with 99mTc sestamibi and one with 99mTc maraciclatide. A radiologist interpreted MBI studies in a randomized, blinded fashion to assign an assessment score (1-5) and measured lesion size. Lesion-to-background (L/B) ratio was measured with region-of-interest analysis. RESULTS Among 39 analyzable patients, 21 malignant tumors were identified in 21 patients. Eighteen of 21 tumors (86%) were seen on 99mTc sestamibi MBI and 19 of 21 (90%) were seen on 99mTc maraciclatide MBI (p = 1). Tumor extent measured with both radiopharmaceuticals correlated strongly with pathologic size (99mTc sestamibi, r = 0.84; 99mTc maraciclatide, r = 0.81). The L/B ratio in detected breast cancers was similar for the two radiopharmaceuticals: 1.55 ± 0.36 (mean ± S.D.) for 99mTc sestamibi and 1.62 ± 0.37 (mean ± S.D.) for 99mTc maraciclatide (p = 0.53). No correlation was found between the L/B ratio and molecular subtype for 99mTc sestamibi (r s  = 0.12, p = 0.63) or 99mTc maraciclatide (r s  = -0.12, p = 0.64). Of 20 benign lesions, 10 (50%) were seen on 99mTc sestamibi and 9 of 20 (45%) were seen on 99mTc maraciclatide images (p = 0.1). The average L/B ratio for benign lesions was 1.34 ±0.40 (mean ±S.D.) for 99mTc sestamibi and 1.41 ±0.52 (mean ±S.D.) for 99mTc maraciclatide (p = 0.75). Overall diagnostic performance was similar for both radiopharmaceuticals. AUC from ROC analysis was 0.83 for 99mTc sestamibi and 0.87 for 99mTc maraciclatide (p = 0.64). CONCLUSIONS 99mTc maraciclatide offered comparable lesion uptake to 99mTc sestamibi, in both malignant and benign lesions. There was good correlation between lesion extent and uptake measured from both radiopharmaceuticals. 99mTc maraciclatide offered a marginal (but not significant) improvement in sensitivity over 99mTc sestamibi. Our findings did not support an association between the uptake of either radiopharmaceutical and tumor molecular subtype. TRIAL REGISTRATION ClinicalTrials.gov, NCT00888589.