Performance of Contrast-Enhanced Spectral Mammography to Assess Neoadjuvant Chemotherapy Response (CEDM)

The use of neoadjuvant systemic therapy in the treatment of breast cancer patients is increasing beyond the scope of locally advanced disease. Imaging provides important information in assessing response to therapy as a complement to conventional tumor measurements via physical examination. Tumor response to neoadjuvant therapy can also provide prognostic information. The attainment of pCR after completion of neoadjuvant therapy and surgical resection is associated with improved disease-free survival. This correlation is especially strong for Triple-receptor negative and human epidermal growth factor receptor 2 (HER-2) positive breast cancer. Studies of neoadjuvant therapy have used a variety of methods for assessing tumor response. Currently, there are no established clinical practice guidelines for how best to assess tumor response to neoadjuvant therapy. Typically, patients undergo conventional breast imaging such as mammography and ultrasonography (US) and physical examination, and dynamic contrast-enhanced breast magnetic resonance imaging (DCR-MRI) in selected cases.

Contrast Enhanced Digital Mammography (CEDM) is a novel imaging technique, which allows digital mammography to be used with contrast enhancement to depict cancers that would otherwise be occult on standard unenhanced mammography. CEDM is performed with and without intravenous iodine contrast, using the dual energy subtraction technique. Compared with mammography and US, CEDM improves the sensitivity for breast cancer detection without decreasing specificity. CEDM digital detector has higher spatial resolution than MRI, revealing details that are approximately 10 times better. In contrast to the rapid washout in MRI, enhancement on CEDM in fact persists for at least 10 min after contrast agent infusion. Today CEDM is available commercially for clinical use. It is estimated that over 200,000 CEDM examinations have been performed to date in both research and clinical settings. CEDM costs significantly less compared to MRI. Furthermore, longer time delays between contrast injection and CEDM exposure could result in stronger enhancement and hence better visibility compared to MRI, especially given the much higher spatial resolution of digital mammography. It is unknown whether CEDM can improve the sensitivity of mammography in the early assessment of neoadjuvant therapy response. We hypothesize that CEDM is superior to mammography and ultrasound in assessing early response, and pre-surgical residual cancer after neoadjuvant therapy, and when performed, non-inferior to MRI in assessing the residual disease using the metrics of pCR and residual cancer burden (RCB).