Features of late local failure of early‑stage non‑small cell lung cancer treated with stereotactic body radiotherapy

Local failure of non-small cell lung cancer (NSCLC) treated with stereotactic body radiation therapy (SBRT) often occurs within 2 years and delayed local failure is uncommon. In the present study, features of late local failure (LLF; >2 years after SBRT) after SBRT were investigated and compared with those of early local failure (ELF; ≤2 years after SBRT) to explore whether these two local recurrence features have different prognostic implications. Patients who underwent SBRT for stage I-IIA NSCLC between July 2006 and March 2014 were retrospectively reviewed. Overall, 173 patients underwent SBRT for NSCLC. The median follow-up times after SBRT were 50 and 31 months for survival and computed tomography (CT) follow-up, respectively. LLF and ELF occurred in 7 and 13 patients, respectively. The median times to LLF and ELF were 42 months (range, 31-61 months) and 13 months (range, 4-16 months), respectively. Local-only failure occurred in 14% (1/7) of LLF cases and 77% (10/13) of ELF cases, which was significantly different (Fisher's exact test, P=0.02). Curative-intent salvage treatment was impossible in all of the LLF cases and 69% (9/13) of the ELF cases, which was significantly different (Fisher's exact test, P<0.01). The median survival times after local failure were 9 and 25 months for patients with LLF and ELF, respectively. Additionally, the 1-year overall survival rates after local failure were 29 and 83% in the LLF and ELF groups, respectively, which was significantly different (log-rank test, P<0.01 at 1-year). In summary, the prognosis after LLF was significantly unfavorable compared with after ELF. Curative-intent salvage treatment is often difficult for LLF due to metastases. Therefore, it seems reasonable to decrease the frequency of follow-up CT for detecting tumor recurrence after the first 2 years post-SBRT.