Microwave Ablation of Colorectal Pulmonary Metastases Offers Excellent Local Tumor Control and Can Prolong Time Off Chemotherapy.

Objective: To evaluate oncologic outcomes after microwave ablation (MWA) of colorectal pulmonary metastases, with focus on disease control without chemotherapy.

Methods: This institutional review board-approved retrospective study examined patients with oligometastatic or oligoprogressive colorectal pulmonary metastases undergoing MWA between January 2011 and December 2021. Imaging response was assessed with CT at 4-8 weeks post-MWA, with subsequent cross-sectional follow-up imaging every 2-4 months. Local tumor progression-free survival (LTPFS), chemotherapy-free survival (CFS) and overall survival (OS) were calculated using Kaplan-Meier methodology. Variables were evaluated for predictive significance using the log-rank test and Cox regression.

Results: Two hundred twenty-five patients (127 male, 98 female; median age: 55 years) with 720 pulmonary metastases underwent 400 MWA sessions (mean number of treated metastases per session: 1.8; range 1-9). Mean treated tumor size was 0.9 cm. LTPFS at 1, 2 and 3-years was 91.9%, 85.9% and 81.5%, respectively. Tumors ≥ 1 cm in size, pleural-based tumors and pre-MWA carcinoembryonic antigen (CEA) levels ≥ 10 ng/mL were associated with shorter LTPFS (all P < 0.001). 74.7% (168/225) of patients did not receive chemotherapy for at least two months after the initial MWA. Median CFS was 12 months (95% CI 7.8-16.2) and was significantly prolonged in patients with lung-only disease compared to those with concurrent extrapulmonary disease (34.4 vs. 4.0 months, P < 0.001). Median OS was 47 months (95% CI 36.7-57.3).

Conclusions: MWA of colorectal pulmonary metastases is associated with high local tumor control rates and can offer prolonged CFS, particularly for patients without concurrent extrapulmonary disease.