Differences in metastatic pattern between 18F-FDG-PET/CT and "CT only" in OMD breast cancer
PD-0241
Abstract
Differences in metastatic pattern between 18F-FDG-PET/CT and "CT only" in OMD breast cancer
Authors: Sophie Pfeiffer1, Rebecca Asadpour1, Lisena Cala2, Wolfgang Weber2, Stephanie E. Combs1, Kai J. Borm1
1Technical University of Munich, Klinikum rechts der Isar, Department of Radiation Oncology, Munich, Germany; 2Technical University of Munich, Klinikum rechts der Isar, Department of Nuclear Medicine, Munich, Germany
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Purpose or Objective
Stereotactic ablative radiotherapy (SABR) of up to 5 metastases has been shown to improve overall survival (OS) in oligometastatic tumor disease (OMD) in previous studies (e.g. SABR-COMET trial). For breast cancer however, there is conflicting evidence regarding the effectiveness of SABR in OMD. An important difference between breast cancer and other entities (such as prostate and lung cancer) is the fact that PET/CT imaging is used less frequently during staging. In the current study, we aim to investigate the impact of 18F-FDG-PET/CT on the pattern of OMD as compared to conventional CT staging.
Material and Methods
All patients in the current study underwent 18F-FDG-PET/CT imaging for breast cancer between 12/2006 and 01/2022 at the Technical University of Munich (TUM). Inclusion criteria were OMD (defined as ≤5 distant metastases) in 18F-FDG-PET/CT and/or CT imaging alone. 81 patients were included in the analyses with 158 18F-FDG-PET/CT images. For all patients, CT imaging findings were reported separately from 18F-FDG-PET findings, allowing comparison of conventional CT imaging and 18F-FDG-PET/CT. For each lesion suspicious of metastasis, we assessed the congruence between CT only and 18F-FDG-PET/CT. Data was analyzed using SPSS. The study was approved by the local Ethics Commission (2022-432-S-NP).
Results
According to the ESTRO/EORTC OMD classification 20% (n = 32) of the cases were De-novo OMD, 43% (n = 68) repeat OMD and 37% (n = 58) induced OMD. In only 32% (n = 50) of the cases, an identical OMD pattern was found in conventional CT imaging and 18F-FDG-PET/CT. In the remaining 108 cases (68 %) there were either differences regarding the number or the localization of the metastases (or both). In 44 % (n = 70) of the cases, the definition of OMD was met only in one of the two imaging modalities (18F-FDG-PET/CT or CT only). In 35% (n = 55) of the cases 18F-FDG-PET/CT revealed additional metastases which were not detected in CT imaging.
Conclusion
Our data demonstrate that the use of 18F-FDG-PET/CT has an important impact on the detected pattern of OMD. This should be considered during interpretation of existing evidence of “OMD breast cancer” and in future trials on the topic.