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PET/MRI assessment of lung nodules in primary abdominal malignancies: sensitivity and outcome analysis
Pierpaolo Biondetti1, Mark G Vangel2, Rita M Lahoud1
1Department of Radiology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, White 270, Boston, MA, 02114, USA.
Purpose:
To evaluate PET/MR lung nodule detection compared to PET/CT or CT, to determine growth of nodules missed by PET/MR, and to investigate the impact of missed nodules on clinical management in primary abdominal malignancies.
Methods:
This retrospective IRB-approved study included [18F]-FDG PET/MR in 126 patients. All had standard of care chest imaging (SCI) with diagnostic chest CT or PET/CT within 6 weeks of PET/MR that served as standard of reference. Two radiologists assessed lung nodules (size, location, consistency, position, and [18F]-FDG avidity) on SCI and PET/MR. A side-by-side analysis of nodules on SCI and PET/MR was performed. The nodules missed on PET/MR were assessed on follow-up SCI to ascertain their growth (≥ 2 mm); their impact on management was also investigated.
Results:
A total of 505 nodules (mean 4 mm, range 1-23 mm) were detected by SCI in 89/126 patients (66M:60F, mean age 60 years). PET/MR detected 61 nodules for a sensitivity of 28.1% for patient and 12.1% for nodule, with higher sensitivity for > 7 mm nodules (< 30% and > 70% respectively, p < 0.05). 75/337 (22.3%) of the nodules missed on PET/MR (follow-up mean 736 days) demonstrated growth. In patients positive for nodules at SCI and negative at PET/MR, missed nodules did not influence patients' management.
Conclusions:
Sensitivity of lung nodule detection on PET/MR is affected by nodule size and is lower than SCI. 22.3% of missed nodules increased on follow-up likely representing metastases. Although this did not impact clinical management in study group with primary abdominal malignancy, largely composed of extra-thoracic advanced stage cancers, with possible different implications in patients without extra-thoracic spread.
Insights
Positron emission tomography/magnetic resonance (PET/MR) has lower sensitivity for detecting lung nodules compared to standard chest imaging. While some missed nodules grew, they did not impact clinical management in patients with primary abdominal malignancies.
Area of Science:
- Radiology
- Oncology
- Medical Imaging
Background:
- Lung nodules are common incidental findings in patients undergoing imaging for primary abdominal malignancies.
- Accurate detection and characterization of lung nodules are crucial for staging and management.
- Positron emission tomography/magnetic resonance (PET/MR) is an emerging imaging modality with potential advantages, but its performance in lung nodule detection needs evaluation.
Purpose of the Study:
- To compare the efficacy of PET/MR in detecting lung nodules versus standard of care imaging (SCI) such as PET/CT or CT.
- To assess the growth of lung nodules that were missed by PET/MR.
- To investigate the clinical management implications of lung nodules missed by PET/MR in patients with primary abdominal malignancies.
Main Methods:
- A retrospective study included 126 patients who underwent [18F]-FDG PET/MR.
- Standard of care chest imaging (CT or PET/CT) within 6 weeks served as the reference standard.
- Two radiologists independently assessed lung nodules on both PET/MR and SCI, with follow-up imaging used to evaluate growth of missed nodules.
Main Results:
- A total of 505 nodules were detected by SCI, while PET/MR detected only 61 nodules, resulting in a sensitivity of 12.1% for nodules.
- PET/MR sensitivity was higher for larger nodules (>7 mm).
- Of the nodules missed by PET/MR, 22.3% showed growth on follow-up, but this did not alter patient management in this cohort.
Conclusions:
- PET/MR demonstrates lower sensitivity for lung nodule detection compared to standard chest imaging, influenced by nodule size.
- A significant proportion of nodules missed by PET/MR exhibited growth, suggesting potential metastatic disease.
- While missed nodules did not impact management in this study group, implications may differ in patients without advanced extra-thoracic disease.
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