Predicting response to neo-adjuvant chemotherapy and assessment of residual disease in breast cancer using contrast-enhanced spectral mammography: a combined qualitative and quantitative approach

Background: Magnetic resonance imaging (MRI) is the gold standard imaging modality for evaluation of response for neo-adjuvant chemotherapy (NAC) in breast cancer as it has the advantage of providing both; morphology assessment together with providing functional information which can be obtained by contrast injection. Until the recent emergence of contrast-enhanced mammography as a promising breast imaging modality, these features were considered unique for MRI. The aim of the study is to evaluate the competence of contrast-enhanced spectral mammography (CESM) in the prediction of response to NAC and the assessment of residual disease extent, as well as the assessment of a new combined (quantitative and qualitative) evaluation approach that is proposed by the authors. The study included 81 patients with pathologically proved breast cancer scheduled for receiving NAC. They underwent 2 CESM examinations; pre- and post-NAC (maximum 10 days before surgery). All patients were assessed using the RECIST 1.1 criteria and a combined approach (RECIST+ qualitative subjective assessment). Results were in correlation to postoperative pathology using the Miller-Payne grading. For statistical evaluation, patients were classified into responders and non-responders. Results: Postoperative histopathology showed that 60/81 lesions were responders (Miller-Payne grades 3, 4, and 5) while the combined response evaluation approach and RECIST 1.1 alone showed 57/60 (95%) patients and 46/60 patients (76.7%) as responders respectively. The combined response evaluation approach showed higher sensitivity and positive and negative predictive values compared to the evaluation based on RECIST alone (95%, 87.6%, and 81.2% compared to 76.6%, 86.7%, and 50% respectively). Conclusion: CESM can be readily used to assess tumor response to NAC and allows the assessment of functional changes in residual tumor cells in addition to size discrepancy. Using CESM, we could accurately assess residual tumor extent and thus enable better surgical planning.