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Local failure of primary lung cancer treated with stereotactic body radiotherapy (SBRT) occurs even after 2-years or more. Differences in prognosis after local failure between early local failure (ELF, recurred within 2-years from SBRT) cases and delayed local failure (DLF, recurred after >2-years from SBRT) cases were investigated.

Consecutive stage I-IIA lung cancer treated with SBRT was retrospectively reviewed. In SBRT, 48 Gy in four fractions at the isocenter was delivered to the primary tumors in principle. Local failure was diagnosed by periodical follow-up CT with or without FDG-PET/CT.

Between 2006 and 2012, 173 lung cancer (stage I, 141; Stage IIA, 32) in 155 patients were treated with SBRT. Twenty-eight tumors recurred locally with or without simultaneous regional and/or distant failure (ELF, 14; DLF, 14). Median time to local failure was 13 months (range 4-23 months) for ELF and 43 months (range 28-94 months) for DLF. Simultaneous regional and/or distant failure tended to be more frequent in DLF compared to ELF (57% vs. 21%; X2-test, p = 0.0530). Prognosis after local failure was significantly poor in DLF cases. Two-year overall survival rates calculated from local failure was 60% for ELF cases and 15% for DLF cases (log-rank test, p=0.0195).

Regarding early-stage lung cancer treated with SBRT, prognosis after local failure was significantly poor in DLF cases compared to ELF cases. In DLF cases, simultaneous regional and/or distant failure tended to be more frequent.