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Local Recurrence Following Transbronchial Microwave Ablation - Risk Factors And Subsequent Management
Joyce WY Chan1, Rainbow WH Lau
1, Aliss TC Chang
1, Clarence HW Chan
1, Cheuk Man Chu
2, Tony SK Mok
3, Calvin SH Ng
1.
1Division of Cardiothoracic Surgery, Department of Surgery, Prince of Wales Hospital, Chinese University of Hong Kong, HKSAR, Hong Kong, Hong Kong,
2Department of Imaging and Interventional Radiology, Prince of Wales Hospital, Chinese University of Hong Kong, HKSAR Prince of Wales Hospital, Chinese University of Hong Kong, HKSAR, Hong Kong, Hong Kong,
3State Key Laboratory of Translational Oncology, Department of Clinical Oncology, Prince of Wales Hospital, Chinese University of Hong Kong, HKSAR, Hong Kong, Hong Kong.
BACKGROUND: Transbronchial microwave ablation with electromagnetic navigation bronchoscopy (ENB) guidance has been a novel technique for treating multifocal lung cancers and lung oligometastases. With its safety and short-term efficacy established by earlier studies, we aim to analyze the risk factors for recurrences and review the subsequent management plan.
METHODS: 235 nodules in 153 patients were treated with ENB transbronchial microwave ablation with intra-operative cone-beam CT support from April 2019 to June 2024. The nodules were evaluated with CT or PET/CT every 6 months for radiological response.
RESULTS: At median follow up of 30 months, 23 cases (9.8%) had confirmed or suspected local recurrence. Two cases were confirmed by biopsy, 5 cases by resection, 14 cases were radiological recurrences, while the remaining two cases were highly suspicious pending confirmation. Nineteen cases were true ablation site recurrences and 4 were intralobar recurrences. Fifteen (65.2%) were primary lung cancers while the rest (34.8%) were metastases. At the time of ablation the nodules were solid in 73.9%, with a mean maximal diameter of 17.7mm and a mean minimal ablation margin of 5.1mm. The mean interval between ablation and relapse was 502 days (range 78-1376 days). For treatment of recurrence, five patients received surgical resection, three received stereotactic body radiation therapy, two underwent successful microwave reablation, and seven received systemic therapy. Compared to those that had not recurred in the same cohort, risk factors for recurrence include solidity (73.9% vs 26.4%, p<0.01) and nodule maximal diameter (17.7mm vs 11.8mm, p <0.02). There was no significant difference between the two groups in terms of bronchus sign, nodule location, and presence of nearby large blood vessels. Upon review of each relapsed case, further potential contributing factors were identified, including small ablative margin <3mm, intra-operative atelectasis which obscured the target nodule leading to inaccurate ablation zone assessement, small intra-operative or 1-month interval ablation zone size on CT, and irregular nodule shape especially dumbbell-shaped.
CONCLUSIONS:Despite the reasonably low local recurrence rate of transbronchial microwave ablation, the local control rate of can be further improved by better case selection. Large solid lung malignancies with irregular shape should be avoided.
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