MR-guided online adaptive stereotactic body radiotherapy (MRgSBRT) of primary lung tumors and lung oligometastases

Stereotactic body radiotherapy is pivotal in the treatment of lung tumors, demonstrating effective local control. However, challenges persist with intra-fractional anatomical changes and organs at risk during delivery. Magnetic resonance-guided online adaptive stereotactic body radiotherapy (MRgSBRT) represents a novel technique promising to achieve safe delivery of ablative doses with improved outcomes for primary lung tumors or lung oligometastases.

In this single-institution retrospective analysis, we evaluated 64 patients (92 lesions) with primary lung cancer or lung oligometastases treated with MRgSBRT. Using Kaplan-Meier method and log-rank test; we estimated local control (LC), local progression-free survival (LPFS), distant progression-free survival (DPFS), and overall survival (OS).

A total of 64 patients (92 lesions) treated with MRgSBRT were included comprising 14.1% primary lung cancer lesions and 85.9% lung oligometastases. Median total dose, fraction number, fraction dose and BED₁₀ were 50 Gy (range, 21–70 Gy), 5 (range, 1–10), 10 Gy (range, 6–34 Gy), 100 Gy (range, 48–180.0 Gy) respectively. Of the 420 fractions administered, 88.6% (n = 372) involved on-table adapted plans. Median LPFS was not reached and the 1‑ and 3‑year LPFS rates were 96.3% (95% CI 92.4–100.0%) and 86.4% (95% CI 76.9–95.9%), respectively. No local recurrences were observed post-treatment with a total dose of > 50 Gy, BED10 > 100 Gy, fractional dose of > 10 Gy or a CCI > 0.96.

Our study of MRgSBRT in 92 lung lesions revealed a 1-year and 3‑year LPFS rates of 96.3 and 86.4%, respectively without ≥ grade 3 toxicity. Future prospective studies evaluating lung MRgSBRT are awaited.