Abstract
BackgroundThe purpose of this study was to use serial magnetic resonance imaging (MRI) examinations to observe changes in malignant lung tumors over time post-cryoablation.MethodsThe study protocol was approved by Institutional Review Board, and written informed consent was obtained from each participant in accordance with the Declaration of Helsinki. Patients with primary or metastatic lung tumors eligible for cryoablation were included in this prospective study. Cryoablation was performed according to standard procedures. Unenhanced and dynamic contrast-enhanced MRI scans were performed pre-cryoablation and at 1 day, 1 week, and 3-, 6-, and 12 months after cryoablation. At each time point, the signal intensity of the ablated zone on both T1WI and T2WI images, and volume and characteristics of the ablation zone were examined, and changes over time analyzed.ResultsA total of 26 nodules in 23 patients were included in the study. The mean patient age was 53.7 ± 13.6 years, and 57.7% were males. Ablation zone volume increased to 1 week after the procedure, and then returned to baseline by 3 months. Cavitation post-cryoablation was found in 34.6% (9/26) of the nodules 1 month after treatment. Two types of time-signal intensity curves post-cryoablation were found: a straight line representing no definite enhancement from 1-day to 1-month, and an inflow curve representing mild delayed enhancement from month 3 to month 12. Local progression was associated with an incomplete hypointense rim around the ablation zone and absence of cavitation post-treatment.ConclusionsCharacteristic changes are present on MRI after cryoablation of lung tumors. A complete hypointense rim and cavitation may be signs of adequate treatment and that local tumor progression is less likely.
Highlights
The purpose of this study was to use serial magnetic resonance imaging (MRI) examinations to observe changes in malignant lung tumors over time post-cryoablation
Nonsurgical candidates are usually managed with systemic chemotherapy; side effects can be severe and not all tumors respond to chemotherapy [3,4,5]
During the post ablation follow-up period, progression was diagnosed by biopsy only if the patient was able to tolerate the procedure, or changes in the nodule such as rapid enlargement or increased glucose uptake were identified on positron emission tomography (PET/computed tomography (CT))
Summary
The purpose of this study was to use serial magnetic resonance imaging (MRI) examinations to observe changes in malignant lung tumors over time post-cryoablation. Surgical resection is the standard treatment for early-stage patients. Percutaneous cryoablation of tumors in the thorax was first reported in 2005 [9], and it has been shown to be safe and effective for lung tumors [3, 5, 10], it is still not widely used for lung malignancies [11]. No tissue is removed during cryoablation; imaging is necessary to determine if the extent of ablation is adequate, and to determine how the lesion has responded to the treatment. Imaging studies are mainly utilized for intra-operative guidance, and there is only 1 report on application of computed tomography (CT) for determination of the ablated zone and the examination of serial post-ablative changes [12].
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