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

PURPOSE

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

MATERIALS AND 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).

CONCLUSION

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.