Stereotactic Lung Re-Irradiation After a First Course of Stereotactic Radiotherapy with In-Field Relapse: A Valuable Option to Be Considered

Background/Objectives: Stereotactic body radiation therapy (SBRT) has demonstrated high local control rates for inoperable early-stage lung cancers. However, 5-15% of patients experience local relapse within the irradiated volume after treatment, with limited curative salvage options. The aim of this review is to clarify the modalities and outcomes after a second course of SBRT in patients with local relapse after a previous lung SBRT. Methods: An exhaustive literature review was conducted to identify, analyse and summarise the results of 21 main studies. Results: Local repeat lung SBRT after a first course of SBRT showed a favourable local control at 1 and 2 years, ranging from 70 to 90% and 45 to 80%, respectively. Good overall survival rates were also observed at 1 and 2 years reaching up to 95% and 85%, respectively. Toxicity was rare but could be severe, with cases of Grade 4 and 5 toxicities (approximate to 5%). An important dose relationship was observed between re-irradiation dose levels and local control, highlighting the importance of precise dosing. The cumulative doses impacting organs at risk were similarly associated with increased radiation-induced toxicity. Central lung lesions presented a higher risk for severe side effects compared to peripheral ones. Conclusions: In conclusion, repeat lung SBRT after a first course of SBRT represents a feasible treatment option in cases of local recurrence. In order to limit severe toxicity, patients must be carefully selected, and particular attention should be given to cumulative doses to organs at risk, as well as tumour location. Thus, further investigations are still needed to refine the optimal parameters for SBRT lung re-irradiation.