Emerging research suggests that positron emission tomography/computed tomography (PET/CT) provides significant advantages over conventional computed tomography (CT) for the management of patients with oligometastatic breast cancer.
For the retrospective study, recently published in the Journal of Nuclear Medicine, researchers compared conventional CT scans to 150 18F-FDG PET/CT images drawn from 80 women with oligometastatic breast cancer. Sixty-one patients (40.7 percent) in the cohort had a previous history of oligometastatic disease (OMD), 57 patients (38 percent) had prior polymetastatic disease and 32 women were diagnosed with metastatic disease for the first time, according to the study.
The researchers found that CT missed additional metastases detected by 18F-FDG PET/CT in 33.3 percent of the cases and detected less than 50 percent of positive lesions diagnosed with 18F-FDG PET/CT in 20.7 percent of the reviewed cases.
Noting that metastases in non-regional lymph nodes accounted for 27.1 percent of the metastases detected in the study and that 24.3 percent of these metastases were only detected with 18F-FDG PET/CT, the study authors said the differences between 18-F FDG PET/CT and conventional CT have significant implications for the use of ablative treatment of OMD.
“A high sensitivity for the detection of metastases is crucial for the concept of ablative treatment in OMD, which requires that all active lesions be treated with curative intent to erase the potential sites of origin for further metastasis or local progression. The persistence of a single unrecognized metastasis can jeopardize the success of ablative therapy in OMD,” wrote lead study author Rebecca Moser, M.D., who is affiliated with the Department of Radiation Oncology at the Technical University Munich School of Medicine and Health in Munich, Germany, and colleagues.
The study authors emphasized that 18F-FDG PET/CT offers a higher yield for diagnosing distant metastases as opposed to CT, noting previous research that indicated a 46 percent sensitivity rate of CT for lymph node metastases.
“This low sensitivity for lymph node metastases can be attributed to the fact that distinction is based solely on the size and shape of the lymph node,” added Moser and colleagues. “18F-FDG PET/CT, on the other hand, provides additional information about metabolic activity, resulting in a better sensitivity for detecting distant metastases.”
Three Key Takeaways
- Improved lesion detection. PET/CT outperforms conventional CT in detecting additional metastases in patients with oligometastatic breast cancer. CT scans missed additional metastases found by PET/CT in 33.3% of cases, highlighting the superior sensitivity of PET/CT for lesion detection.
- Enhanced sensitivity for distant metastases. PET/CT offers higher sensitivity for diagnosing distant metastases compared to CT alone, especially in non-regional lymph nodes. This higher sensitivity is attributed to PET/CT providing metabolic activity information in addition to anatomical data, which aids in detecting distant metastases.
- Critical for ablative treatment planning. The study underscores the importance of PET/CT in ablative treatment planning for oligometastatic disease. Ablative therapy requires treating all active lesions with curative intent, and PET/CT's higher sensitivity ensures that potentially overlooked metastases are addressed, crucial for the success of ablative therapy in oligometastatic breast cancer.
(Editor’s note: For related content, see “Current Perspectives on PET/CT Imaging in Patients with Metastatic Breast Cancer,” “Positron Emission Tomography and De-Escalation of Breast Cancer Treatment: What Emerging Research Reveals” and “MRI-Based AI Model Shows Promise in Predicting Lymph Node Metastasis with Breast Cancer.”)
While the researchers acknowledged that CT found more metastases in 46.7 percent of the cases than 18F-FDG PET/CT, they pointed out that most of these patients had inactive metastases with normal glucose metabolism due to receiving systemic therapy prior to PET imaging. The study authors also maintained that 36 percent of OMD cases were revealed only on 18F-FDG PET/CT.
“ … Use of only conventional CT is not suitable to reliably detect oligopersistent or oligorecurrent disease. In conventional CT, distinguishing between active metastases and inactive residual metastases is not feasible,” emphasized Moser and colleagues. “However, bone scintigraphy in additional to conventional CT is likely to mitigate the large disparities observed in this study between 18F-FDG PET/CT and conventional CT.”
Beyond the inherent limitations of a retrospective study, the authors noted differences between 18F-FDG PET/CT and CT in defining OMD as opposed to directly comparing the accuracy of the two imaging modalities. The researchers also conceded the possibility of false-positive findings due to the comparison of 18F-FDG PET/CT with its CT component. The study authors added that patients with brain metastasis or a history of a second malignancy were excluded from the study.
