The Use of Molecular Breast Imaging to Assess Response in Women Undergoing Neoadjuvant Therapy for Breast Cancer

Abstract

To report our findings from a prospective pilot study evaluating the accuracy of molecular breast imaging (MBI) in assessing tumor response to neoadjuvant therapy (NT) for breast cancer. Twenty patients with newly diagnosed invasive breast cancer who were scheduled to receive NT underwent MBI before beginning and after completing NT before surgery. MBI was performed using a dual-detector cadmium-zinc-telluride gamma camera system mounted on a modified mammography gantry after patients had received an intravenous injection of 20 mCi of 99mTc sestamibi. Tumor extent was measured on MBI, and tumor-to-background (T/B) ratios of radiotracer uptake were determined through region-of-interest analysis. Pathologic measurement of tumor size was used as a standard and compared with post-NT tumor size derived from MBI. Three patients in whom post-NT MBI could not be performed because of scheduling problems were excluded from analysis. Eighteen cancers were diagnosed in 17 patients. A correlation coefficient of r = 0.681 (P = 0.002) was found between MBI and residual tumor size. The average T/B ratio on MBI decreased from a pretreatment value of 3.0 to a posttreatment value of 1.4. The relative decrease in T/B ratio did not appear to be predictive of response. Measurements of tumor size by MBI and T/B ratios are limited in their predictive value regarding the pathologic extent of residual disease in women treated with NT for breast cancer. Alternate tumor-specific radiopharmaceuticals should be evaluated to provide information to improve planning and monitoring of breast cancer treatment.