Low-Burden Oligometastatic Disease of the Lung Treated with Robotic Stereotactic Ablative Radiotherapy: A Retrospective Study.

Background/Objectives: The lung is the most common site of metastases, regardless of the cancer subtype. Treating oligometastatic disease with surgery or stereotactic ablative radiotherapy (SABR) may improve patient survival. Methods: We retrospectively analyzed 41 patients with limited (one or two lesions, max dimension <3 cm) lung-only metastatic disease that were treated with the CK M6 robotic radiosurgery system in our Department, in terms of treatment efficacy and toxicity. Results: Acute and late toxicity was negligible (4 out of 41 patients developed grade 2 or 3 lung fibrosis). Six months post-SABR, complete response was achieved in 18 out of 41 patients (43.9%), while the rest of the cases exhibited major responses. A biological effective dose (BED_α/β=10) in the range of 100 Gy appears to be equally effective with higher doses. Within a median follow-up of 34 months, only three patients (7.3%) progressed locally, while three patients progressed to distal sites. Two-year local progression-free survival (LPFS) rates were 92.6% (95% CI 78.5-97%). Conclusions: SABR for low-burden lung oligometastases is an effective treatment modality that yields high local control and survival rates. Toxicity is negligible, regardless of the performance status of patients. Early referral of such patients to radiation oncology departments may be critical for patient survival and quality of life.