ACCURACY OF PET/MRI FOR ESTIMATING RESIDUAL TUMOR AFTER NEOADJUVANT CHEMOTHERAPY IN PATIENTS WITH INVASIVE BREAST CANCER

Abstract

Breast cancer is the most frequently diagnosed cancer and the leading cause of cancer death among women worldwide.Neoadjuvant chemotherapy has a well-established role in the treatment of invasive breast cancer. Initially used only for locally advanced breast cancer, it can be offered to all patients who would benefit from adjuvant systemic chemotherapy, enabling early assessment of the chemotherapy response, improving surgical options and reducing mortality. Early and accurate assessment of tumor response to therapy can help to individualize treatment regimens and avoid ineffective treatment choices.Traditional methods such as mammography and ultrasonography are not adequate to monitor treatment response, since they fail to distinguish fibrotic lesions from residual tumors.Magnetic Resonance Imaging (MRI) is a widely used method for this purpose, with relative good accuracy. However, it may underestimate or overestimate the residual tumor. The efficacy of 18F-FDG PET/CT has also been studied, but it does not seem to be accurate in the evaluation of small tumors.There is evidence that 18F-FDG PET/CT has greater sensitivity and MRI a greater specificity in the evaluation of response of the neoadjuvant therapy in patients with breast cancer. The combination of these two imaging methods in the integrated PET/MRI method is expected to provide better information and may have great potential to improve the diagnostic performance.Our project is novel and aims at investigating the accuracy of the integrated PET/MRI method in the identification of residual lesions in patients with invasive breast cancer that have been treated with neoadjuvant chemotherapy. To this end, 57 patients with breast cancer and axillary lymph node involvement will be evaluated by PET/MRI in addition to the routine staging exams which include biopsies and imaging methods. The findings of the PET/MRI scans will be correlated with those obtained by the histopathological analyses of the tissues removed at surgery. The working hypothesis is that the PET/MRI will be of even better accuracy than the information provided by PET scan and MRI as independently performed. However, should it have an accuracy comparable to either of these, still the integrated PET/MRI method would particularly benefit those patients who are candidates for both MRI (for breast lesions) and 18F-FDG PET/CT (whole body scan), enabling a single exam, lower radiation exposure, lower total examination time and better correlation between the methods, with potentially better accuracy at evaluating the response to neoadjuvant chemotherapy. (AU)