[¹⁸F]FDG in recurrent breast cancer: diagnostic performances, clinical impact and relevance of induced changes in management

Prognosis and management of patients with recurrent breast cancer depend on the spread of the disease. The aim of this study was to evaluate the performance of fluorine-18 fluorodeoxyglucose gamma camera positron emission tomography (FDG-GPET) in detecting breast cancer recurrence, its clinical impact and the relevance of induced changes in management. Patients (n=134) with suspicion of recurrence either clinically or on conventional imaging (suspected recurrence: SR) or with an isolated increase in tumour marker levels (occult recurrence: OR) underwent FDG-GPET on a coincidence gamma camera. The reference standard for evaluation of accuracy, either histology (n=26) or follow-up for 1 year (n=49), was available in 75 (56%) patients. A questionnaire was sent to the referring clinician to evaluate the impact of FDG on management. Responses were obtained for 75 patients. Information regarding both approaches was available for 46 patients (46/134=34%). At the patient level, the sensitivity of FDG-GPET was 84%, significantly higher than the 63% sensitivity for conventional modalities, and the specificity was 78% versus 61%. The values for FDG-GPET were 81% and 86% respectively in the SR group and 90% and 73% respectively in the OR group, without any significant difference between these settings. The rate of change in management was 44% overall, 43% in the SR group and 45% in the OR group. Within the two groups, intermodality (major) changes were more frequent than intramodality (minor) changes. In the 46 patients for whom both approaches were available, 93% of management modifications were relevant (validated by biopsy or clinical follow-up). The results of this retrospective study show that FDG-GPET has an important role to play in patient management by confirming and evaluating the extent of recurrence or by localising occult recurrence