Ablative Techniques for Lung Metastases: Outcomes of Patients Treated with Stereotactic Radiotherapy and Radiofrequency Ablation

Stereotactic radiotherapy (SBRT) and radiofrequency ablation (RFA) are common ablative techniques for lung metastases. Retrospective review of all patients treated with either modality at a single institution between 2011 and 2019 was conducted. Baseline characteristics and outcomes were compared. Local and distant progression, and overall survival were estimated using the Kaplan Meier method. Univariable analysis was carried out using Cox regression followed by multivariable modeling. 106 patients treated with RFA and 70 treated with SBRT were identified. Tumours treated with SBRT were larger (median size 18 vs 11mm) and primarily oligometastatic (91.4% vs 20%). Median progression-free survival (PFS) was 12.5 months for SBRT and 7.9 months for RFA (p=0.009). Median OS was similar (p=0.66). In multivariable analysis, lesion size >20mm was predictive of adverse local PFS (p=0.001), PFS (p=0.0034) and OS (p=0.001). Statistically significant interaction effect suggested RFA offered better local PFS compared to SBRT within colorectal primary patients (p=0.035). This study highlights differences in patient baseline characteristics, selection and outcomes for RFA or SBRT in the treatment of lung metastases at our institution. Future studies for SBRT should focus on the radiosensitivites of individual tumour types and the optimum dose schedules required for differing histologies. For less radiosensitive tumours, RFA may offer a superior alternative.