Whole-body 18F-fluorodeoxyglucose positron emission tomography-computed tomography (18F-FDG PET/CT) for staging locally advanced breast cancer: A prospective study from a tertiary cancer centre in south India

Background & objectives: Locally advanced breast cancer (LABC) is associated with substantial risk of occult metastases. The patients with LABC have high rate of systemic relapse, suggesting inadequacy of the current conventional staging in detecting the occult metastatic spread. 18F-fluorodeoxyglucose (FDG) positron emission tomography-computed tomography (PET/CT) is a new modality in the staging of breast cancer patients. Hence, this study was conducted to evaluate the role of 18F-FDG PET/CT in initial staging of LABC and to compare it with conventional methods. Methods: This prospective study included biopsy-confirmed female patients diagnosed with LABC meeting the selection criteria and attending surgical, medical and radiation oncology departments of a tertiary care centre in south India, from April 2013 to December 2014. Conventional workup included serum chemistry, mammogram, bone scan, contrast-enhanced CT (CECT) chest and upper abdomen and ultrasound abdomen and pelvis. All patients following conventional workup underwent 18F-FDG PET/CT. Results: In this study, 61 women with LABC underwent both conventional workup and 18F-FGD PET/CT. The 18F-FDG PET/CT, in comparison to conventional workup, revealed unsuspected N3 nodal disease in 11 more patients, revealed distant metastasis in seven more patients and also detected extra sites of metastasis in five patients. The sensitivity, specificity, positive predictive value, negative predictive value and accuracy of PET/CT to detect distant metastasis were 95, 98, 95, 98 and 97 per cent, respectively, whereas the sensitivity, specificity, positive predictive value, negative predictive value and accuracy of conventional imaging to detect distant metastasis were 65, 93, 81, 84 and 84 per cent, respectively. Interpretation & conclusions: The 18F-FDG PET/CT was found to be more accurate than conventional imaging for staging and modified stage and treatment in 30 and 38 per cent of patients, respectively. It was particularly useful in detecting occult distant metastasis and N3 nodal disease with an added advantage of examining whole body in single session. However, CECT chest was superior over 18F-FDG PET/CT for detecting pulmonary metastasis