Combining evidence and practice: evaluating proton re-irradiation in recurrent lung cancer.

[BACKGROUND] Locoregional recurrence of lung cancer after definitive radiotherapy remains a clinical challenge. Although re-irradiation offers curative potential, its application is limited by cumulative toxicity to organs at risk. Proton re-irradiation therapy (PRT) provides favorable dosimetric properties that may mitigate treatment-related adverse events (AEs).

[METHODS] We conducted a meta-analysis of eight studies including 343 patients with recurrent lung cancer treated with PRT. Outcomes assessed included overall survival (OS), progression-free survival (PFS), and AEs. Additionally, a single-center retrospective cohort of 12 patients treated with PRT between November 2023 and April 2024 was analyzed as real-world evidence.

[RESULTS] The pooled 1-year and 2-year OS rates were 62% and 45%, respectively; the corresponding PFS rates were 47% and 28%. The incidence of grade ≥3 AEs was 22%, and grade 5 AEs occurred in up to 10.5% of patients. In the institutional cohort, the 1-year OS was 66.7%, with only one patient (8.3%) experiencing a grade ≥3 AEs.

[CONCLUSION] PRT demonstrates promising efficacy and acceptable safety in patients with recurrent lung cancer. While these findings are encouraging, they should be interpreted cautiously given the limited high-level evidence, and prospective randomized studies are needed to further define the role of PRT relative to photon-based re-irradiation.